WILDLIFE MANAGEMENT PLAN

FOR TORREY PINES STATE RESERVE

TERRESTRIAL VERTEBRATES

November 1997

Revised December, 1998

A Report Prepared Under the Resource Preservation Grant Program of the California Department of Parks and Recreation

ACKNOWLEDGEMENTS

Project Manager: Michael Wells, Associate Resource Ecologist, San Diego Coast District

Interim Manager: Dr. Jamie King, Environmental Services Intern, San Diego Coast District

Field Coordinator: Stacie Hathaway, Environmental Services Intern, Torrey Pines State Reserve

Field Assistant: Jamie King, Environmental Services Intern, San Diego Coast District

Report Preparation:

Habitat Mapping Summary: Michael Wells

Vertebrate Survey Summaries: Jamie King

Introduction and Recommendation Implementation Sections: Mike Wells and Karen Miner, Associate Resource Ecologist, Southern Service Center

Mapping: Darren Smith and Paul Ison, GIS specialists, Southern Service Center

Report Editing: Marla Mealey, Archaeological Lead, Southern Service Center, Karen Miner, Mike Wells, Jamie King and M.Jean Smith

Contractors:

Habitat Mapping: D. Stow, S. Phinn, B. Nyden and M. Henry, Center for Earth Systems Analysis and Research, Department of Geography, San Diego State University

Mammalian Carnivore Study: Kevin Crooks, Department of Biology, University of California, Santa Cruz

Herpetofauna Study: Robert N. Fisher and Ted J. Case, Department of Biology, University of California, San Diego

Sensitive Avifauna Survey: Jon Gibson, Darren Irwin, and Trevor Price, Department of Biology, University of California, San Diego

Special Thanks to:

The staff of Torrey Pines State Reserve

Torrey Pines Docent Society, especially John Carson, President

and the many volunteers and landowners adjacent to the Extension, who contributed to the success of this project.

TABLE OF CONTENTS

1. INTRODUCTION

1.1 Key Concepts and Underlying Assumptions

1.2 Overview

 2. HABITAT MAPPING 2.1 Introduction

2.2 Habitat Classification
 

2.2.1 Upland Habitat Types 2.2.1.1 Torrey Pine Forest and Woodland
2.2.1.2 Southern Maritime Chaparral
2.2.1.3 Bare Ground
  2.2.2 Wetland Habitats

2.2.3 Salt Marsh Habitats

2.2.3.1 Bare Soil/Panne/Sand
2.2.3.2 Riparian
2.2.3.3 Grasses   2.3 Trends and Long-Term Change
          2.3.1 Uplands
          2.3.2 Wetlands 3. PREDATOR AND MESOPREDATOR SURVEY 3.1 Introduction

3.2 Materials and Methods

3.3 Results and Discussion
 

3.3.1 Relative Abundance

3.3.2 Distribution

3.3.2.1 Bobcats
3.3.2.2 Coyotes
3.3.2.3 Smaller Carnivores
  3.3.3 Corridors 3.3.3.1 Sorrento Valley Corridor
3.3.3.2 Portofino Corridor 
3.3.3.3 Pacific Coast Highway
3.3.3.4 Crest Canyon
3.3.3.5 Los Peñasquitos Creek
3.3.3.6 Carmel Valley Corridor
3.3.3.7 Carmel Mountain Corridor 3.3.4 Characteristics of Functional Corridors 3.3.4.1 Size
3.3.4.2 Structure 3.3.5 Community Effects : Housecats, Coyotes and Mesopredator Release

3.3.6 Relation of Species Sensitivity to Habitat Fragmentation

3.3.7 Comparison of Study Methods

 3.4 Recommendations for Predators
  3.4.1 Corridor Preservation and Enhancement 3.4.1.1 Pacific Coast Highway
3.4.1.2 Carmel Valley Corridor
3.4.1.3 Sorrento Valley Corridor
3.4.1.4 Land Acquisition 3.4.2 Continued Monitoring

3.4.3 Halting Human Disturbance

3.4.4 The Railroad Issue

3.4.5 Public Education

 4. REPTILE AND AMPHIBIAN SURVEY 4.1 Materials and Methods

4.2 Results of Herpetofauna Survey
 

4.2.1 Species Present

4.2.2 Diversity

4.2.3 Distribution and Sensitivity

4.2.4 Status of Sensitive Snakes and Lizards

4.2.4.1 Coast Horned Lizard (Phrynosoma coronatum)
4.2.4.2 Coastal Western Whiptail (Cnemidophorus tigris multiscutatus)
4.2.4.3 Orange-Throated Whiptail (Cnemidophorus hyperythrus)
4.2.4.4 Coronado Skink (Eumeces skiltonianus interparietalis)
4.2.4.5 California Legless Lizard (Anniella pulchra)
4.2.4.6 San Diego Ring-Necked Snake (Diadophis punctatus)
4.2.4.7 Two-Striped Garter Snake (Thamnophis hammondii)
4.2.4.8 Red Diamond Rattlesnake (Crotalus ruber)
4.2.4.9 Coastal Rosy Boa (Lichanura trivirgata)
4.2.4.10Coastal Patch-Nosed Snake (Salvadora hexalepis virgultea)
  4.2.5 Historic Numbers 4.2.5.1 Snakes

4.2.5.2 Lagoon Species

4.2.5.3 Other Species
 

 4.2.6 Activity Patterns 4.2.6.1 Amphibians
4.2.6.2 Lizards
4.2.6.3 Snakes
  4.3 Results of inadvertant Rodent captures
  4.3.1 Distribution 4.3.1.1 Mice
4.3.1.2 California Meadow Vole (Microtus californicus)
4.3.1.3 Shrews (Notiosorex and Sorex)
  4.3.2 Rodent Activity Patterns 4.3.2.1 Mice
4.3.2.2 Voles
4.3.2.3 Shrews
  4.4 Areas of Special Concern

4.5 Recommendations for Herpetofauna
 

4.5.1 Exotic Species

4.5.2 Physical Modifications

4.5.3 Enforcement

4.5.4 Education

4.5.5 Corridor Creation

 5. AVIFAUNA SURVEYS 5.1 Introduction

5.2 Trends

5.3 Habitat Affiliations

5.4 Conservation Issues

5.5 Individual Species Summaries
 

5.5.1 Belding’s Savannah Sparrow (Passerculus sandwichensis beldingi)

5.5.2 California Least Tern (Sterna antillarum browni)

5.5.3 Light-footed Clapper Rail (Rallus longirostris levipes)

5.5.4 Snowy Plover (Charadrius alexandrinus nivosus)

5.5.5 Coastal Cactus Wren (Campylorhynchus brunneicapillus)

5.5.6 California Gnatcatcher (Polioptila californica californica)

5.5.7 Least Bell’s Vireo (Vireo bellii pusillus)

 6. Implementation of Recommendations 6.1 Introduction

6.2 Assumptions

6.3 Means of Implementation

6.4 Criteria for Prioritizing Actions

6.5 Actions Recommended
 

6.5.1 Internal Actions

6.5.2 Internal Actions with Funding Required

6.5.3 Cooperative Actions

6.5.4 Cooperative Actions with Funding Required

 7. References

INTRODUCTION

The primary purpose of the State Park System is to preserve the indigenous aquatic and terrestrial flora and fauna of California’s various ecological regions, including the southern coastal strip (Public Resources Code 5019.53). Torrey Pines State Reserve, including Peñasquitos Marsh Natural Preserve (Reserve), is unique in that it is one of the only large areas (1,256 acres) of natural coastal habitat left within the city limits of San Diego, and is therefore an important contributor to regional habitat and faunal preservation. Historically, the Reserve was the western terminus of a band of undeveloped land that extended from the coastal mountains to the Pacific Ocean. With the urbanization of San Diego, this band of natural open space has become increasingly compressed and riddled with urban enclaves. Recent development in the Carmel Valley, Carmel Mountain, and Sorrento Valley areas has substantially reduced the open space connection of the Reserve to habitat to the east. This apparent loss of connectivity is of concern to park managers and ecologists, because it likely means that several of the large wildlife species (deer, mountain lion and bobcats, etc.), and potentially even some smaller species (reptiles, rodents, etc.), will no longer use the Reserve. Based on current knowledge of effects of habitat fragmentation, the loss of these species will likely have a "domino" effect and result in the loss of additional species within the Reserve. The ability of the Reserve to maintain faunal diversity also depends on the amount and condition of the various wildlife habitats within the Reserve. These habitats can be affected by both management practices within the Reserve and by changes in land use and conditions upstream or bordering the Reserve. Currently, there are many non-department development projects proposed or in process, that will likely affect wildlife populations in the Reserve area, both directly and indirectly. Mitigation measures for impacts from these projects are being determined without fully knowing the possible range and relative significance of impacts, or appropriate measures for reducing these impacts. It has become apparent that a wildlife management plan needs to be developed that identifies specific strategies and actions needed to maintain the current faunal diversity, based on specific knowledge of the distribution and density of various key species and their habitats within the Reserve.

With this in mind, the State Park System, using funds from the Resource Preservation Grant Program, initiated a project to determine the status of wildlife populations, their habitats, and the management actions critical to the preservation of faunal diversity within the Reserve. The project consists of four focused studies:

The underlying aim of these studies is to ascertain the current status of several suites of sensitive or ecologically important species and to compare this information with that gained from previous studies, in order to determine population trends and to recommend appropriate management actions for the curtailment of the loss of species. Components of the research for this project were identified in the Torrey Pines State Reserve Natural Resources Inventory and Monitoring Program (California Department of Parks and Recreation [CDPR] 1995), and are listed in that document as I-1, I-8, M-9, and M-13 through M-21.

This document 1) presents and summarizes the results of the four studies, 2) identifies specific management strategies and actions necessary for maintaining the current faunal biodiversity of terrestrial vertebrates at The Reserve, and 3) organizes these recommended actions according to priority and means of implementation. In addition to providing California State Parks with a plan for preserving faunal biodiversity within the Reserve, this document is intended to be complementary to the City of San Diego’s Multiple Species Conservation Program (MSCP) and shared with all agencies enrolled in the program so that habitat linkages can be coordinated region-wide. It is to be noted that these are baseline studies, designed to support a definitive decision-making process.
 

 Key Concepts and Underlying Assumptions

Research within the last ten years on the effects of preserve design and habitat fragmentation has demonstrated that isolation of natural areas ultimately results in the loss of species therein (Soulé et al. 1988, 1991). The size of the fragment and the amount of time since its isolation determine the number of species existing in the "island" of habitat. Relatively small habitat patches (less than a few square miles) cannot support a self-sustaining population of wide ranging species such as large vertebrates. Many of these large vertebrates are top predators, such as the mountain lion, bobcat and coyote, and are often referred to as "keystone predators". The loss of these keystone predators creates an imbalance in the wildlife community, which leads to further loss of species due to a process known as "mesopredator release". This occurs when some species (smaller predators, such as fox, skunk, and domestic cats) increase in abundance at the expense of their prey (birds, rodents, insects, reptiles and amphibians). If these prey species are already at low numbers within the fragment, as is the case with rare or sensitive species, they are more susceptible to being eliminated from the area.Populations of species with limited numbers of individuals are already subject to possible extinction due to the effects of chance events, such as disease, extremes in weather, genetic drift, and gender bias. These random events can effectively wipe out a population of a given species within a localized area, especially if the size of the population is low. Loss of species to chance events is said to be caused by demographic (characteristics of the population) or environmental "stochasticity". The number of individuals of a species required to maintain a healthy, viable population that persists through time in spite of stochastic events depends on many factors and is specific to each species within the context of the particular habitat fragment. However, a general rule of thumb derived from theoretical and empirical field data is that 500 individuals are required for species with average natural fluctuations in population size, such as birds and large mammals, and 5,000 individuals for species with large natural fluctuations in population size, such as some rodents and insects. This number is referred to as the "minimum viable population" size. To be conservative, some researchers suggest that these numbers should be doubled to permit long-term persistence (Thomas 1990).The long-term maintenance of populations is also partly dependent on the genetic diversity of the population. The more genetic diversity a populations has the more likely it will be able to adapt to changes in the environment or local conditions, such as disease, habitat disturbance, habitat alterations, presence or absence of other species, etc. If a population is too small, the individuals interbreed among themselves, and any deleterious genes are more readily passed on to the next generation. The population then reduces in size and continues to decline in a downward spiral towards extinction. This is referred to as "inbreeding depression". A population is said to be "genetically viable" if the number of successfully reproducing individuals, or "effective population size", adequately represents the whole population in terms of its genetics. The minimum number of individuals required for a population to be genetically viable depends on many factors and is species specific, but generally 500 successfully reproducing individuals has been estimated as the required minimum for long term survival of a species. A minimum of 50 successfully reproducing individuals is the estimated requirement to avoid inbreeding depression. Clearly, maintaining 500 successfully breeding individuals of every species is not possible within the Reserve alone, especially for the large vertebrate species. Even 50 individuals would be difficult for some species, including bobcats, mountain lions (both keystone predators), and listed species such as California Gnatcatchers, and clapper rails (See Section 5.5 this volume). For this reason it is essential to consider the connection that the Reserve has with other wildlife habitat in the vicinity.There are two ways to increase the number of individuals in the effective population, and both will have to be employed at the Reserve. One is to increase the carrying capacity of the land base through habitat enhancement measures, such as removal of competing non-native species, restoration of natural ecological processes, and by decreasing disturbance factors. The other is to assure exchange of breeding individuals between other populations of the species through maintenance of dispersal corridors physically connecting "subpopulations" thereby allowing passive exchange of individuals, or through actively transporting individuals between isolated "metapopulations". The term "subpopulations" refers to a subset of a species whose members most often breed with other members of the same subset, but for which there is some exchange of breeders with other subsets of the species. The term "metapopulation" refers to a subset of a species, or collection of subpopulations, that is geographically isolated from other such metapopulations of the species. Whether the individuals of a particular species at the Reserve represents a subpopulation or a metapopulation of that species depends on the natural dispersal abilities of that species and the current physical distance to other groups of individuals of that species. For example, a bird will have no problem crossing a river, but the same obstacle could effectively isolate two populations of a lizard. Another example is that a bird with a typical dispersal distance of eight miles has the ability to breed with individuals located or dispersing within that distance, but if the nearest population of this species is 30 miles away, the two populations may be considered effectively isolated from each other. Thus, different species will require different strategies for the maintenance of genetic exchange between populations in order for the species to persist within the Reserve. However, to maintain the presence of keystone predators and reduce the risk of mortality for animals crossing urban landscapes, it will be necessary to maintain connectivity of habitat, not only within the Reserve, but also between the Reserve and other nearby natural open space and faunal populations.The suite of species surveyed as part of this study (mammalian carnivores, reptiles, amphibians and rare birds) were chosen because of their particular vulnerability to habitat fragmentation and environmental disturbance. By basing management and conservation strategies on these species, we hope to address the most critical threats, not only to the persistence of these species, but to the long-term preservation of the entire wildlife community at Torrey Pines State Reserve.  

 Overview

The 1,256 acres within the Torrey Pines State Reserve are already divided into distinct subunits by topography and roads (Figure 1.1). The "Main Reserve," the area around the lodge on the terrace south of the lagoon, includes the Torrey pine forest, coastal bluff, and shrub habitats between the beach and the Pacific Coast Highway (also known as North Torrey Pines Road). Los Peñasquitos Lagoon and the surrounding upland habitats including salt marsh, freshwater marsh, and subshrub phase of Southern Maritime Chaparral, comprise the "Lagoon" subunit and is bordered by North Torrey Pines Road on the west, Carmel Valley Road on the north and Sorrento Valley Road on the east. The railroad berm running through this area somewhat further divides it into northeast and southwest components. The third subunit is referred to as the "Extension." This area, which is set apart from the rest of the Reserve, is comprised of Southern Maritime Chaparral, and a small grove of Torrey pines. Carmel Valley Road and a residential area occupy the intervening area between the Extension and the Lagoon.

One only has to look at early topographic maps (e.g., 1953 Del Mar 7.5 minute quadrangle) and aerial photographs (Figures 2.1 through 2.8) to see that the Extension and Lagoon areas were once broadly connected to Del Mar Mesa (and thence to San Dieguito Valley), Carmel Valley, Carmel Mountain, Los Peñasquitos Canyon, Mira Mesa (Kearney Mesa), and Carroll Canyon, with only a few narrow transportation routes bisecting these broad corridors (i.e., Sorrento Valley Road, Carmel Valley Road, Fourth Street Extension, and the Santa Fe Railroad). At that time the main Reserve had been separated from lands to the east by Pacific Coast Highway for some time. According to a 1975-revised topographic map, connectivity to the north and east of the Reserve had been all but severed by the construction of Interstates 5 and 805. In addition, development had occurred in Sorrento Valley and the mouth of Los Peñasquitos Canyon. To the north Del Mar Heights was being developed, separating the Extension from the San Dieguito Valley. By 1992 (in Ogden Environmental and Energy Services Company [Ogden] 1992) residential and commercial development had greatly reduced the amount of natural habitat in Del Mar Heights, Carmel Valley, and on Mira Mesa. Most recently, construction of Highway 56 and its exchange with I-5, and additional development in Sorrento Valley and Carmel Valley have essentially severed connectivity of the Reserve to lands directly east.

Effects from this development were realized within the Reserve as water runoff, debris, and silt were discharged into the creeks and lagoon from these expanding urban areas. This has led, in part, to an increase in the amount of sediment deposited within the lagoon (Mudie and Byrne 1980), which has elevated portions of the land area thereby effecting the type and distribution of vegetation and bare ground within the lagoon. This conversion of vegetation types is further exacerbated by the accompanying increase in freshwater input into the system. The increase in freshwater flow of Peñasquitos Creek is evidenced by the fact that in 1980 the U. S. Geological Service reclassified it from intermittent to a perennial stream. It is hypothesized that the current freshwater emergent and riparian vegetation types, as well as many invasive non-native species, have become established and expanded at the expense of saltmarsh vegetation in the eastern part of the lagoon as a result of the increased inputs of sediment and freshwater. The amount and types of chemicals transported into the system through this urban runoff (lawn fertilizers, road oil, etc.) and their impacts are unknown.

It may be that a naturally functioning lagoon system, receiving natural tidal flows, could possibly accommodate these anthropogenic perturbations. However, the lagoon mouth of Los Peñasquitos is constricted to the width of the Pacific Coast Highway bridge and several of the tidal channels are cut off by the railroad berm. These physical barriers altered the manner and extent of tidal influence within the lagoon and the composition and distribution of habitat has changed accordingly (See Section 2.3 this volume).

All of these changes in and around the Reserve have altered its ecology and its relationship to adjacent natural areas such that the Reserve’s natural assemblage of animals may not be able to continue to exist. It appears that at least five species of vertebrates examined in this study have become extirpated from the park since the 1960s. These include:

Least Tern, Sterna antillarum (breeding)

Snowy Plover, Charadrius alexandrinus (breeding)

Red Diamond Rattlesnake, Crotalus ruber

Long-nosed Snake, Rhinochelius lecontei

Mountain Lion, Felis concolor

 It is possible that an additional six species of snakes also disappeared from the Reserve during the same time period based on trapping records in the vicinity (See Section 4.2.5 this volume). Other species may have been extirpated prior to that time but earlier occurrence records are unavailable for comparison. The four studies summarized in the following sections were conducted in order to augment existing spotty occurrence records, and document the current abundance and distribution of terrestrial vertebrates and their habitat, in order to provide baseline information for management of the Reserve in hopes that further loss of species diversity can be avoided.
 

HABITAT MAPPING

Introduction

The amount and distribution of suitable habitat is an essential element to consider for the management of wild faunal populations. Many species are obliged to inhabit particular vegetation types, while others may require a variety of habitat types for different phases of their life cycles or to fulfill particular life history requirements. Consideration of the spatial arrangement of various habitat types is crucial when assessing the probability of whether a viable population of a particular species may persist within some geographically defined area. In Torrey Pines State Reserve, many sensitive taxa are dependent on specific habitat types. This is especially the case for endangered avifauna (Gibson and Price 1996). The intent of this portion of the project is to map the distribution of various habitat types, as defined by physical site characteristics and vegetation, within the boundaries of the Reserve. Ultimately such information can support management activities such as indicating where vegetation restoration efforts can be focused in order to increase the amount of suitable habitat for sensitive species, or to enhance connectivity between habitat patches.The habitat type maps for this project were produced by the Department of Geography at San Diego State University (Plate I). A summary of the procedures used is included in Appendix A (Stow et. al. 1996).The habitat maps of the wetlands within Los Peñasquitos Lagoon were produced from ADAR imagery taken by Positive Systems Inc. during overflights of the lagoon on October 18, 1994 and September 24, 1995. The images were orthorectified with kinematic global positioning system (GPS) data to a horizontal positional accuracy of less than two meters. Classification of the images was a supervised, automated procedure using reference information taken from training sites established within the lagoon.The habitat map of the upland portion of the lagoon was compiled using a different procedure. Images of terrestrial vegetation often include a high level of non-vegetative reflectance such as earth and rock. This problem prevents effective use of automated classification. The habitat coverage for the upland portion of the Reserve was manually interpreted from ADAR images referenced to 25 vegetation sampling sites. Initially a one-hectare minimum mapping unit size was to be applied to the habitat map, however use of the supervised automated procedure for the lagoon allowed a finer level of resolution to be achieved for the wetland areas.
 

Habitat Classification

The habitat classification system used for this study is based loosely on Holland (1986) for upland habitats and Zedler et al. (1992) for wetland habitats. The first order division in the system is based on physical site characteristics, in this case the difference between upland and wetland habitats. This approach was necessitated by the different image classification techniques, as described above, applied to these different areas. Also, the purpose of this project is to map habitat types rather than floristic associations. Physical site characteristics are important aspects to consider when assessing the suitability of a particular site as habitat for fauna.
 

Upland Habitat Types

The second order divisions of the upland habitat types were taken from the element descriptions in Holland (1986). Third order divisions were based on dominant life-form and cover as described below. Diagram of dominant plant life forms in the Uplands

Torrey Pine Forest and Woodland

Torrey Pine Forest represents those areas where Pinus torreyana ssp. torreyana, a federal species of concern, has established an essentially closed canopy. These areas are found in the northern upland portion of the main reserve and the southern portion of the reserve extension. The shade under the closed canopy creates a moist microhabitat. Common understory plants in the Torrey pine forest are Coreopsis maritima and Dichondra occidentalis (Ferreira 1982).Torrey pine woodland is composed of areas where Torrey pines are an important component of the vegetative community but do not establish a closed canopy. Conditions are generally warmer and drier at these sites than under a closed canopy. Common associates within the Torrey pine woodland are elements of Southern Maritime Chaparral such as chemise (Adenostoma fasciculatum), wartystem ceanothus (Ceanothus verrucosus), flat-topped buckwheat (Eriogonum fasciculatum), lemonade berry (Rhus integrifolia), as well as less common shrubs with more mesic affinities such as bush poppy (Dendromicon rigida), toyon (Heteromeles arbutifolia), and Fuscia-Flower Gooseberry (Ribes speciosum).

 

The chart below illustrates the relationship of habitat classifications used here to previous work in the area by Holland (1986) and Sawyer and Keeler-Wolf (1995).
 
Habitat type Holland 1986 Sawyer and Keeler-Wolf 1995
Torrey Pine Forest Torrey pine forest 83140 
(Page 98)		 Torrey pine stand Page 326)
Torrey Pine Woodland Torrey pine forest 83140 
(Page 98)		 Torrey pine stand Page 326)
 

Southern Maritime Chaparral

The habitat type name is borrowed from Holland (1986) but as used in this study is not homologous to it. In the Reserve this habitat type is a complex mixture of species dominated by different life forms including shrubs, sub-shrubs, and herbs. There is some affinity between soil type and dominant life form. Sub-shrubs and herbs are predominant on the coarser, better-drained soils in the northwestern part of the main Reserve. Woody shrubs are predominant on the finer textured soils derived from near-shore marine deposits in the southeastern portion of the park. This edaphic affinity, however, is not consistent throughout the mapped area.In comparing the current habitat map to an earlier study (Ferreira 1982) it is apparent that distribution by life form within this larger habitat type may be dynamic and at least in part related to disturbance history. Herbs tend to dominate in the most frequently disturbed areas while shrubs and sub-shrubs are often predominant at more stable sites. Because of this ambiguity it was decided to class all of these upland non-tree dominated areas as Southern Maritime Chaparral. However, at the suggestion of the researchers conducting the avifauna and herpetofauna surveys, this larger class was subdivided into three phases based on dominant life form.The validity of this subdivision was supported by the results of a Twinspan classification performed on data from 35 upland vegetation transects recorded at the sites of the herpetofauna pitfall trap arrays. The primary division in the classification of the non-tree-dominated sites is based on the presence or absence of Adenostoma fasciculatum as a dominant. Within this division the main associates of Adenostoma fasciculatum are spice bush (Cneoridium dumosa), black sage (Salvia mellifera), and mission manzanita (Xylococcus bicolor). This is the shrub-dominated phase of Southern Maritime Chaparral.Those areas not dominated by Adenostoma tend to have high cover values of California sagebrush (Artemisia californica) and flat-topped buckwheat (Eriogonum fasciculatum), with lemonade berry (Rhus integrifolia) and non-native grasses as common associates. The presence of Rhus not withstanding, these areas are classed as sub-shrub dominated Southern Maritime Chaparral, though there is an obvious similarity to Holland’s (1986) Diegan coastal sage scrub.Along the maritime exposure of Guy Fleming Grove and Parry Grove, below the sub-shrub Southern Maritime Chaparral and Torrey pine woodland respectively, is a vegetation type that includes sub-shrub elements. This vegetation type includes Eriogonum sp., golden bush (Isocoma menziesii), California bush sunflower (Encelia californica), and (in Parry Grove) cliff spurge (Euphorbia misera), but is largely composed of herbaceous vegetation. Conspicuous elements of this vegetation include bird’s beak (Cordylanthus rigidus ssp. setigerus), wand chicory (Stephanomeria virgata ssp. virgata), beach primrose (Camissonia cheranthifolia ssp. suffruticosa), sand verbena (Abronia umbellata), deer weed (Lotus scoparius), California poppy (Eschscholzia californica) as well as several species of non-native grasses. In addition, in several areas this vegetation includes a well-developed succulent component including coast prickly pear (Opuntia littoralis), coast barrel cactus (Ferocactus viridescens), and ladies’ fingers (Dudleya edulis). This vegetation type is located on steep slopes intermittently disturbed by wind and water erosion. As a result, invasive exotics frequently become established there, including: sea fig (Carpobrotus edulis), Russian thistle (Salsola tragus), European stock (Mattholia incana), ripgut brome (Bromus diandrus), and recently veldt grass (Ehrharta longiflora). This is a highly diverse assemblage to group under a single classification, however, the minimum mapping unit size for the upland portions of the reserve is one hectare and it would be difficult to split this classification into smaller units without employing a finer level of spatial resolution. Because this vegetation type shares some species with the two preceding classifications, and is often intermixed with them, it is classified as herb dominated southern coastal chaparral.

The following chart shows the relationship of terminology used in this paper to that of previous work.
 
Habitat type Holland 1986 Sawyer and Keeler-Wolf 1995
Southern Maritime Chaparral    
   Shrub Southern Maritime Chaparral 
37C30 (Page 98)		 Chamise-Mission Manzanita 
(Page 137)
   Sub-shrub Diegan Coastal Sage Scrub 
32600 (Page 10)		 Calif. Sagebrush-Calif. Buckwheat (Page 127)
   Herb Southern Coastal Bluff Scrub 
31200 (Page 7) 

Southern Foredunes 
21230 (Page 2)

 Calif. Encelia 
(Page 123) 

Calif. Buckwheat 
(Page 120)
 

Bare Ground

This classification is usually used to indicate areas devoid of plant life. At the Reserve soils are highly erosive and precipitation is variable from year to year. Episodes of high erosion and deposition of sediments are intermittent and unpredictable. Thus the spatial distribution of this habitat type is dynamic. In addition, portions of the Reserve have been subjected to anthropogenic disturbances during the past. The southern end of the Reserve’s uplands was used as a military training site during World War II, and several old jeep trails still remain from this period. Other areas of the Reserve were used as campgrounds, parking, and picnic areas prior to State ownership. Also, the removal of exotic plants by Reserve staff and volunteers during the last decade has resulted in the creation of small bare areas, which may persist for longer than a single year.It is worth discussing bare ground because of the relationship of two endemic species, short-leaved dudleya (Dudleya blochmaniae ssp. brevifolia), and Torrey pines (Pinus torreyana), to this type of substrate. D. blochmaniae ssp. brevifolia, listed by the state of California as endangered, is a small cryptophyte that is found, in the central Reserve and Reserve extension on highly eroded sites around the bare margins of mesas in shallow sandy soils. At least one of the three other existing populations of D. blochmaniae ssp. brevifolia is found on a similar type of substrate, approximately three miles east of the Reserve on Carmel Mountain.Seedlings of P. torreyana also have an affinity for bare soil. The few naturally occurring seedlings found in recent surveys of the Reserve (McMaster 1984, Cario and Zedler 1996, Wells 1996) were found in areas cleared by natural or human disturbance.

Wetland Habitats

As described above the mapping of wetland habitats was a supervised automated classification of ADAR imagery. The habitat classifications are based on the floristics of the plant assemblages and the ability of the image classification routine to distinguish between classes. The habitat types are modified from Zedler et al. (1992) as that work was focused on a southern California estuary and reflects important transitions in community composition that are not recognized by either Holland (1986) or Sawyer and Keeler-Wolf (1995).The division of wetland vegetation classes is not as distinct as that of the Reserve’s uplands. The dominant physical and chemical site characteristics are soil salinity and inundation, neither of which has a monotonic trend in relation to other environmental gradients. Periods of inundation are greatest near the mouth of the lagoon and high in the lagoon near fresh water inflows. Soil salinity is positively correlated with elevation in the low salt marsh and negatively correlated with elevation above this range. Additionally, not all classes could be distinguished on the basis of the ADAR imagery. Classifications have been generalized accordingly. In the following dendrogram the mapped classifications are represented in bold type. The first three orders of division are based on physical site characteristics, they are respectively: wetland versus dry, saline versus fresh and elevational gradation. A third division is made at the secondary order for disturbed habitats. The fourth order division is based on dominant lifeform or taxa.

 Salt Marsh Habitats

Salt marsh vegetation is stratified by relatively minor changes in elevation, which are negatively correlated with frequency and duration of tidal inundation, and positively correlated with soil salinity (Pennings and Callaway 1992). In Los Peñasquitos Lagoon the lowest level, from about 2 to 4 feet above mean sea level, is occupied almost exclusively by pickleweed (Salicornia virginica). Above this nearly mono-specific habitat is a more diverse assemblage of plants capable of tolerating occasional tidal inundation and relatively high levels of salinity. The elevational range of this community is approximately from 5 feet to about 10 feet above mean sea level. Its dominants are fleshy-leaved jaumea (Jaumea carnosa), alkali heath (Frankenia salina), salt grass (Distichlis spicata), S. virginica, and another species of pickleweed (S. subterminalis). Two infrequent species important because of their regional rarity are San Diego marsh-elder (Iva hayesiana) and sea-blight (Suaeda esteroa). A common non-native that invades this habitat type above the level of tidal inundation is Carpobrotus edulis. Another exotic that commonly invades areas subject to fresh water intrusion is curly dock (Rumex crispus).
 
Habitat type Holland 1986 Sawyer and Keeler-Wolf 1995
Salicornia Southern Coastal Salt Marsh 
52120 (Page 46)		 Pickleweed (Page 71)
Mid-high salt marsh Southern Coastal Salt Marsh 
52120 (Page 46) 		 Pickleweed (Page 71)
 

Bare Soil/Panne/Sand

These areas are lumped together because of the similarity of their reflectance signatures. In the central and eastern lagoon large mud flats occur which are typified by highly saline soils. These are, for the most part, devoid of vegetation. An interesting exception is Coulter’s goldfield (Lasthenia glabrata ssp. coulteri) that tends to grow in the cracks of the dried mud (Boland personal communication) and is a federal species of concern.Bare sand areas are found along the northwestern margin of the lagoon. In two areas these support remnant coastal foredune communities, although these areas are smaller in size than one hectare. This association is best developed on a small dune on the southwestern edge of the lagoon immediately east of the south beach parking area. Common elements of the vegetative assemblage for this area consist of Camissonia cheranthifolia ssp. suffruticosa, Abronia umbellata, Lotus scoparius, Nuttall’s lotus (L. nuttalianus) (a federal species of concern), Opuntia littoralis, Dudleya edulis and arrow weed (Pluchea sericea).
 
Habitat type Holland 1986 Sawyer and Keeler-Wolf 1995
Sand Southern Foredunes 
21230 (Page 2)		 None
 

Riparian

Riparian vegetation areas are those communities within the lagoon influenced by predominantly fresh water inflows, although, at any point in time the water on these sites may be brackish to some degree. This category includes assemblages dominated by emergent monocots such as species of cattail (Typha spp.), rushes (Juncus spp.), sedges (Carex spp.), and bulrush (Scirpus spp.). Also included in this classification are riparian shrublands and woodlands dominated by mule fat (Baccharis salicifolia) and arroyo willow (Salix lasiolepis). These habitats are frequently invaded by a large number of exotic species. The most common of these include giant reed-grass (Arrundo donax), pampas grass (Cortaderia jubata), castor bean (Ricinis communis), tamarisk (Tamarix sp.), and tree tobacco (Nicotiana glauca). The riparian woodlands in the far southern end of the lagoon support a large population of the unusual (for San Diego) exotic catalpa tree (Catalpa bignonoides).    
Habitat type Holland 1986 Sawyer and Keeler-Wolf 1995
Riparian    
Monocot Coastal Brackish Marsh 52200 (Page 47) 

Coastal and Valley Fresh water Marsh 52410 (Page 48)

 Bulrush (Page 35) 

Bulrush-Cattail (Page 37) 

Cattail (Page 42)
Shrubland-woodland Mule Fat Scrub 63310 
(Page 64) 

Southern Willow Scrub 63320 
(Page 64) 

Central Coast Arroyo Willow 

Riparian Woodland 63230 
(Page 53)

 Mule Fat (Page 179) 

Arroyo Willow (Page 219) 

 
 

Grasses

Grasslands in the lagoon occur above elevations of about six feet, overlapping the upper elevational range of mid-high marsh. Grasslands appear to become established in disturbed areas that are high enough to avoid tidal inundation. The lagoon grasslands are composed of a mix of several species of common exotic grasses: oats (Avena spp.), brome (Bromus spp.), barley (Hordeum spp.), perennial ryegrass (Lolium perenne), as well as the native perennial wildrye (Leymus condensatus).    
Habitat type Holland 1986 Sawyer and Keeler-Wolf 1995
Grassland Non-native grassland 42200 
(Page 36)		 California annual grassland 
(Page 40)
 

Trends and Long-Term Change

Uplands

Vegetative assemblages are not static over time but are dynamic in response to climatic trends and site disturbance. The following trends have been noted in the upland vegetation in the Reserve:

1) Lack of reproduction in Torrey pine woodland and forest. McMaster (1980), Cario and Zedler (1996), and Wells (1996) have noted the lack of Torrey pine seedlings in most of the recently undisturbed portions of the Reserve. Cario’s (1997) work indicates that competition with shrubs and herbs suppresses the growth of Torrey pine seedlings, and that seedlings benefit from the removal of competing vegetation. Seedlings have been located in areas subject to wildfires (McMaster 1980), and to prescribed burning (Scheidlinger and Zedler 1986; Wells 1996). Seedlings are also apparent along the margins of roads and trails in the northern, upland portion of the main Reserve. Dendrochronological (tree-ring) analysis of increment bores taken in the Reserve indicate that the oldest trees are in the neighborhood of 160 years old (Biondi 1997). McMaster (1980) showed that the modal age category for Torrey pines in the Reserve was 56-83 years (at that time). This suggests that the majority of the P. torreyana population in the Reserve may now be close to or in excess of 100 years of age, raising the possibility that Torrey pine woodland and forest may diminish in cover in the absence of future disturbance within the Reserve. During the years 1988-1992 approximately 10 percent of the mature Torrey pine population died due to infestation by the dendroctonus beetles: Ips paraconfusus and Dendroctonus valens. Insect attacks may not create opportunities for seedling establishment because they do not suppress shrub species that compete with seedlings. The systematic introduction of disturbance in the form of prescribed fires could create opportunities for recruitment of Torrey pine seedlings (Scheidlinger and Zedler 1986) and reverse long-term population decline.

 2) Spread of exotic annual grasses. As with most small natural areas in southern California, the Reserve has been invaded by numerous exotic plant species. Over 133 taxa of exotic plants have been identified in the Reserve (Jacobson 1995). Control efforts have been focused on the highly invasive species such as Carpobrotus sp., Salsola sp., and Matthiola sp. and have achieved some success. However, removal of these exotics has created opportunities for exotic graminoids to become established. These species intermingle with native herbs and can eventually displace them. In general these species are small, annual and seed prolifically. An effective means of control has not as yet been identified. In the absence of effective control it is likely that the amount of area vegetated in annual exotic grasses will expand within the Reserve.

3) Other exotics. Two other species of exotic plants that are highly invasive and have not yet been effectively controlled are black mustard (Brassica nigra) and fennel (Foeniculum vulgarae). Brassica nigra has become established in the scar of a 1992 wildfire that burned the eastern exposure of the main Reserve. There has been only patchy recovery of natives within the fire scar. Brassica nigra has also become established in an old agricultural field to the east of Flintcote Road. Only a few individual desert elderberry (Sambucus mexicana) shrubs have become established there. Foeniculum vulgarae has become established along the shoulders of roadways throughout the Reserve. In other locations in southern California it has been able to become established and exclude competing native plants in a manner similar to Brassica nigra. Methods of controlling these two species within the Reserve should be explored.

 

Wetlands

Trends in vegetation change in Los Peñasquitos Lagoon have been driven by anthropogenic change within the watersheds of Carmel, Sorrento, Los Peñasquitos, and Carroll Canyon Creeks. Mudie and Byrne (1980) and Cole and Wahl (unpublished data) found that sedimentation rates within the lagoon greatly increased in the 1850s coincident with the clearing of large portions of the watershed for agricultural development. The stripping of natural vegetation from the watershed has increased the amount of freshwater runoff and erosion. This has led to increased inputs of freshwater and sediment to the lagoon. Salt marsh vegetation is stratified over relatively minor changes in elevation (Pennings and Callaway 1992). Sedimentation can cause agradation of the areas receiving sediment inputs. Increased fresh water input alters the balance between salt and fresh water within wetlands favoring some species over others.

1) Expansion of Salicornia spp. into panne. Aerial photographs of the lagoon taken in 1929 (Figures 2.1and 2.5) show extensive areas of bare soil on both the east and west sides of the railroad right-of-way. The bare areas were likely caused by heavy sedimentation that occurred from 1850 to 1900 as a consequence of the clearing in the lagoon watershed for agriculture (Mudie and Byrne 1980). Since 1929, aerial photos taken in 1953, 1973, and 1993 (Figures 2.1 through 2.8), and 1996 ADAR imagery, have revealed a progressive reduction in the size of these bare areas. In the western lagoon these areas are generally below an elevation of three feet (Tekmarine 1991), and now support Salicornia spp. salt marsh. Cole and Wahl (unpublished data) examined and quantified amounts of pollen taken from sediment cores in the western lagoon. They found that the amount of pollen from the Chenopodiaceae (most probably Salicornia spp.) decreased during the early settlement period and then increased during this century. This fluctuation may correspond to Salicornia sp. in the salt marsh being buried by sedimentation and then the subsequent recolonization of the resultant mudflats.

2) Expansion of exotics into bare areas. In the eastern lagoon, bare areas apparent in 1929 air photos presently are at elevations of five feet and above. These areas now support a mix of mid-high marsh, exotics and grasses. If sufficient fresh water is present at such sites, as is the case in the northeastern lagoon, such disturbed areas support a mix of riparian natives and exotics with hydric affinities (Arundo donax, Carpobrotus edulis, Cortaderia sp., etc.).

3) Expansion of riparian and exotics into salt marsh. Examination of historic air photos and 1996 ADAR imagery show that willow woodland and Baccharis sp. scrub have become established in the eastern and southern portions of the lagoon in relatively recent times. Presumably this is because of agradation due to sedimentation and year-round inputs of fresh water. It is likely that such expansion has come at the expense of mid-high salt marsh.
 

Other evidence also supports this perceived trend. Analyses of pollen in sediment cores by Cole and Wahl (unpublished data) indicate that the amounts of pollen from Salix are greatest in the most recent sediments. Annual monitoring of four vegetation quadrats in the eastern lagoon by the Pacific Estuarine Research Lab from 1991 to 1996 (Williams 1996) indicates a transition in composition from predominantly salt marsh species to predominantly riparian and exotic species at three of four sites. The fourth site was already predominantly riparian and exotic in 1991. This indicates that transitions from salt marsh to brackish marsh or riparian can take place with surprising rapidity.

A similar process has taken place along the western shoulder of Carmel Valley Road. In that area alluvial fans have accumulated at storm drain outlets leading from the Del Mar Terrace area. Year-round fresh water flows are also associated with the storm drains. Prior to development it is likely that the vegetation of these areas was Salicornia spp. and mid-high salt marsh, as are surrounding areas. Over time, as sediments have accumulated, these fans have become covered in a mix of exotic species including Carpobrotus edulis, Nicotiana glauca, Acacia cyclops, and Myoporum sp. Restoration of the alluvial fans is possible because of their proximity to Carmel Valley Road, and would involve removal of the accumulated sediments along with vegetative restoration.

PREDATOR AND MESOPREDATOR SURVEY

Introduction

Large to medium sized carnivores are especially impacted by habitat fragmentation because of their need for significant home ranges, low population densities, and slow population growth rates. For this reason, Kevin Crooks explored the abundance and distribution of large to medium-size mammals within the Torrey Pines State Reserve over a two-year period (Crooks 1997). Such studies contribute important baseline data that can provide indications of the health and stability of the wildlife community in the various sections of the Reserve, in terms of balance between keystone predators and mesopredators. Building on a study by Ogden (1992), Crooks also determined the current status of previously functioning wildlife "corridors" connecting the Reserve to other patches of suitable habitat. The characteristics of functioning corridors were also reviewed. A summary of Crooks’ 1997 report, and relevant excerpts of Ogden’s 1992 report follow.
 

Materials and Methods

 Four standard sampling methods were used to estimate the distribution, relative abundance, movement patterns, and potential corridor usage by large mammals visiting the Reserve. The methods used were: 1) scat surveys along transects, 2) track counts of animals attracted to scent lures also along transects, 3) remotely triggered cameras located at track stations, and 4) questionnaires distributed to residents adjacent to the Extension. Five areas were surveyed: the Main Reserve, the Extension, Los Peñasquitos Lagoon, Crest Canyon, and Sorrento Valley corridor. With the exception of Sorrento Valley, which was surveyed only during Fall 1996, sampling occurred seasonally over the Fall 1995 - Summer 1996 period.

Figures 3.1 and 3.2 are orthophotographs of the Reserve showing the location of mammal survey stations and transects, as well as potential wildlife corridors. Figure 3.1 covers the Extension and northern portion of the Lagoon, and Figure 3.2 covers the southern portion of the Lagoon and the Main Reserve. Figures 3.3 and 3.4 show the same information as in Figures 3.1 and 3.2, but in relation to mapped vegetation associations. See Section 2 this volume for descriptions of the vegetation classes.

Results and Discussion

Relative Abundance

Track and scat surveys revealed similar trends, and evidence from the questionnaires corresponded well with the surveys. Scat evidence of coyote visitation (283 total scats) along transects was by far the most abundant, followed by bobcat (67), and fox (48). A similar ordering was found for the tracking data of the larger predators: coyotes (281) and bobcats (46). Evidence of mesopredator visitations was abundant. The number of visitations to track stations for each species were: skunks (122), opossum (27), raccoon (24), fox (21), domestic dog (71), and domestic cat (5) (Table 1 in Crooks 1997).  There was no evidence of mountain lion visitations.

Distribution

Bobcats

Bobcats were found most frequently in the Main Reserve and along Flintkote Road (eastern edge of the Lagoon) (Figure 3.2). Occasional visitations were documented in the Extension. Because of the small size of the Extension (1 km2), one would expect only occasional use by a few bobcats since individual home ranges average 10-20 km2 (Nowak and Paradiso 1983). It is likely that bobcats are visiting from the eastern Lagoon via the Portofino corridor (Figure 3.1).

Coyotes

Distributed throughout the area, coyotes were present in highest relative abundance in the Extension, Crest Canyon, and near the golf course adjacent to the southern part of the Main Reserve. The Extension population appears to be divided into two groups: one at the north end and the other along the Red Ridge Trail to the south. Less activity was observed on the Parry Grove and Guy Fleming trails in the upland area, and on Flinkote Road and along the southwest Lagoon trail.

Smaller Carnivores

Smaller mesopredators tended to be associated with degraded habitats and were more prevalent in the Extension and Los Peñasquitos Lagoon. Fewer visitations were found in the upland portion of the Reserve (Figure 3 in Crooks 1997).

 Corridors

One of the most practical and effective measures to maintain wildlife in urban settings is the establishment of linkages that permit dispersal across barriers such as roadways and developments (Noss 1983, 1987; Soulé 1991; Soulé and Gilpin 1991; Noss et al. 1996). These linkages are called wildlife corridors, and for functionality they must fulfill several needs (Ogden 1992): 1) the corridor must link two or more patches of isolated habitat; 2) the corridor must conduct animals to areas of suitable habitat without excessive risk of directing them into a "mortality sink" - an unsuitable area with high risk of mortality; 3) the corridor design must allow individuals of the target species to use the corridor frequently enough to facilitate demographic and genetic exchange between separated populations. Where functional movement corridors are not retained across the urban landscape, many wildlife populations, especially large carnivores, will eventually disappear.Seven wildlife corridors have been studied in the past five years. Figure 3.5 shows those corridors studied by Ogden in 1992, and Figures 3.1 and 3.2 show the corridors studied by Crooks in 1997. Corridors have been designated as either "functional" - defined by the consistent usage by all target species (deer, mountain lion, bobcat, and coyote); "partially functional" – not used by the largest mammals (deer and mountain lion); and "non-functional" – not used by any target species. Of these corridors three were found "functional" in 1997 (Sorrento Valley, Portofino, and Pacific Coast Highway), three "nonfunctional" (Crest Canyon, Los Peñasquitos Creek, and Carmel Mountain), and one of unclear status (Carmel Valley). The functionality of the corridors in many cases has changed from their 1992 status, presumably in response to development pressures along corridor routes.

Sorrento Valley Corridor

Contrary to Ogden's 1992 report, the Sorrento Valley Corridor was the only functional wildlife corridor to areas outside of the Torrey Pines Reserve in Crooks’ 1997 study. A corridor previously labeled as functional by Ogden (1992), the Carmel Mountain Corridor (labeled F-1 in Figure 3.5), no longer appears to be used, apparently due to construction and development over the last five years. No evidence of the use of the Sorrento Valley Corridor by mule deer, bobcats, or mountain lions was found in 1992. The pressure of the development of Carmel Mountain Road has likely been the cause of their "switching" to the Sorrento Valley linkage.

There are at least two routes used by predators and mesopredators through the Sorrento Valley Corridor. The northern route starts at the west end of Los Peñasquitos Canyon, passes under I-805 and I-5, goes along the lawn south of the business complex on Sorrento Valley Road, passes under Sorrento Valley Road, and ends in Los Peñasquitos Lagoon. The southern route starts on the east side of Los Peñasquitos Canyon, passes under I-805 and I-5, goes past the J & R Redwood Co. on Sorrento Valley Road, goes under Sorrento Valley Road, and ends in Los Peñasquitos Lagoon. Both routes follow the natural riparian channel between Los Peñasquitos Lagoon and Los Peñasquitos Canyon (Figure 3.2).

Six species have been found to use the Sorrento Valley Wildlife Corridor. All species use both routes within the corridor. Bobcats and coyotes use the corridor several times a month, while evidence of the coyote, fox, and raccoon are found almost nightly. Opossums and skunks frequently use the wildlife corridor. No deer tracks were found, and this is likely due to the low underpass limiting the use of the corridor by deer. No mountain lion tracks were found either, however, this may be due to the fact that the duration of past surveys was too short to register a rare event.

As the only functional corridor between the Reserve and other core areas, the restoration and protection of the Sorrento Valley Corridor is vital. Crooks (1997) recommends the following measures to ensure the functionality of the Sorrento Valley, not only for the species currently utilizing it, but for the mountain lion and mule deer as well.

Portofino Corridor

The Portofino Corridor begins at the southeast corner of the Extension, goes across Portofino Road and Carmel Valley Road, and ends at Los Peñasquitos Lagoon. Coyotes, foxes and occasionally bobcats use this route, although there is no evidence that mule deer and mountain lion do. As the best linkage of the Extension to larger natural areas, it is imperative to maintain and enhance this functional corridor. The open space link at the northeast junction of Portofino and Carmel Valley Roads should be protected. Any widening of the Carmel Valley Road should incorporate a structural wildlife corridor to allow interchange between Los Peñasquitos Lagoon and the Extension.

Pacific Coast Highway

The Pacific Coast Highway bisects the eastern and western portions of the Reserve. As the number of road kills has shown (Ogden 1992), species including mule deer and large carnivores cross this road to access other portions of the Reserve. Any increase in traffic or widening of the road would severely impact connectivity and should be preceded by a plan to facilitate crossings. Posting signs to motorists designating this area as an animal crossing may help to decrease road kills.

Crest Canyon

This corridor is mainly nonfunctional. Coyotes may travel from the northern end of the Extension, across Del Mar Heights Road, through the urban matrix, and into Crest Canyon (Figure 3.1). However, extensive housing and traffic on Del Mar Heights Road appear to prohibit much use of this corridor.

Los Peñasquitos Creek

Ogden (1992) found this corridor to be a mortality sink. Animals move from Los Peñasquitos Lagoon, west along I-5 to the Genesee Avenue/I-5 intersection. They are then funneled into a cul de sac and forced to cross Genesee Avenue, where the likelihood is great that they will be hit in traffic.

Carmel Valley Corridor

Although this corridor was functional for mountain lion, bobcat, coyote, and fox in 1992 (Ogden 1992), it was not thoroughly surveyed by Crooks in 1997 because the freeway was under construction. Crooks (1997) recommends that current construction plans be analyzed and construction be monitored to ensure a functional corridor is created. As of this writing, two I-5 bridges have been constructed over the Carmel Valley Creek channel. These parallel bridges measure approximately 8 feet high and 40 feet wide, and together they cover an over 200-foot stretch of the creek. It has not yet been determined if wildlife will accept this underpass as a viable route of travel (see Section 3.3.4 below), or if it is now or will remain accessible to wildlife.

Carmel Mountain Corridor

The Carmel Mountain underpass was used by deer, mountain lions, bobcats, and coyotes in 1992 (Ogden 1992), but it is no longer functional. In 1992, wildlife could travel west from Del Mar Mesa, down Carmel Mountain Road, then across a small dirt road. West of the I-5 underpass, the corridor turned north and followed a narrow coastal sage scrub berm between I-5 to the east and an industrial park to the west. At the north end of the industrial park, the corridor turned west and followed a chaparral vegetated ravine to Sorrento Valley Road. Animals crossed the two lane road and railroad tracks before entering Peñasquitos Lagoon and the Main Reserve. It is likely that this corridor has been permanently severed due to additional office development on the west side of I-5, widening and paving Carmel Mountain Road through the underpass, and current housing construction on the east side of I-5.

Characteristics of Functional Corridors

A 1992 study of corridors in San Diego County (Ogden 1992), defined characteristics common to functioning wildlife corridors. Functional corridors were generally well vegetated, over 500 feet wide at the narrowest portion, had water year round, and if underpasses were present, they were well covered with vegetation and had noise levels ranging from 40-56 decibels. Road kills were found to decrease for certain types of underpass structures. Mortalities were lowest for bridge type underpasses and increased for pipe culverts, box culverts and interchanges respectively. These criteria should be taken into account when evaluating potential new corridors.

Size

Corridor widths (excluding buffer zones) are recommended to be no less than 500 feet and should be determined by topography. A buffer of native vegetation should exist at least 250 feet on both sides which functions to hide the animals and make human intrusion difficult. It is best to use the entire topographic feature (e.g., canyon) as a corridor, as it stops animals from climbing slopes and decreases human encroachment and development.For areas less than 400 feet wide, corridor length should be less than 500 feet. When traversing urban development, or when a topographically separated corridor is unavailable, the corridor width must be much greater and extensively vegetated with native habitat. As the length of a corridor and/or frequency of human encroachment increases, so does the need for a wider, higher quality, and more secluded corridor.

Structure

Corridors should be located within a topographic feature and must be well vegetated along the outer edges and within. A year round water source is necessary, preferably with a riparian strip. As animals tend to follow a path of least resistance, a dirt trail should be provided. Ten-foot fences (deer may be able to leap shorter fences) are needed to funnel animals into underpasses. To remain effective these fences need to be maintained. If underpasses are unavoidable, unlit, well-vegetated, bridge-type underpasses are the best solutions. Animals may prefer bridges with length no greater than twice the width, but this is less of a factor when the bridges are high. It is recommended to create a space between opposing traffic lanes to allow air and natural light through to the passage below. Mountain lions rarely use culverts, therefore this type of underpass is not preferred in areas where lions are present. Human encroachment should be minimized, especially transients living under overpasses. The corridor should not lead to a habitat cul-de-sac which will function as a mortality sink. Business parks should be well vegetated with native plants to minimize views of the building and to afford animals a protected passage. When a human recreation area is part of the corridor, adequate cover should be provided for animals to hide in during the day.
 

Community Effects : Housecats, Coyotes and Mesopredator Release

Crooks (1997) notes that the disappearance of top predators (mountain lions, coyotes, bobcats) from native habitat patches may have community wide implications. Because large carnivores can suppress the abundance of smaller ones through competition and predation, they can also affect the relative abundance of prey species. For example, the decline of coyotes in an area may lead to the increase of small predators such as gray foxes, raccoons, striped skunks, opossums and domestic cats. While coyotes prey primarily on rabbits and rodents, the smaller carnivores tend to prefer birds, nests and other small vertebrates. Thus, the disappearance of large predators from an area can result in "mesopredator release", an increase in smaller carnivores and an associated change in the relative abundance of prey species.Crooks’ ongoing Southern California study examines these hypotheses. In general he has found that different carnivore species show varied vulnerability to habitat fragment size, isolation, and age since isolation. Mountain lions, bobcats and spotted skunks were found to be most sensitive to fragmentation, while fox, opossum, raccoon and domestic cat populations increased with fragment size decrease. Of special interest is the correlation between coyote abundance, fragment size and the occurrence of mesopredator release. He found that while coyotes did well in disturbed urban settings, the smaller the habitat patch, the less likely coyotes were to be present, and that the absence of coyotes can result in mesopredator release.Because the Reserve has resident coyotes, mesopredator release is not an immediate threat. This does not mean however that mesopredators, especially house cats, are not having a severe impact on local wildlife. Coyotes help control cat numbers through predation, as shown by cat hair in coyote scats. However, there are hundreds of residences surrounding the Extension, with an estimated one-third owning cats, while there are probably only one or two pairs or family groups of predators such as fox or coyote in the same area. Extrapolating from questionnaire responses and other data, Crooks estimated that local cats may be killing hundreds of prey each year, many of which are native species.
 

Relation of Species Sensitivity to Habitat Fragmentation

Noss et al. (1996) suggested that predators may be excellent species on which to base management and conservation strategies as they are particularly vulnerable to habitat fragmentation and environmental disturbance. As part of a larger study throughout San Diego county, Crooks has been analyzing the relationship of predator presence and abundance to habitat size, isolation from other habitat patches and age since patch isolation. His preliminary results suggest strategies applicable to the management of the Reserve.The choice of a target species for monitoring is scale sensitive. Given the size of habitat patches within the Reserve, bobcats are considered by Crooks (1997) to be the best large predator for monitoring. Existing now in large enough numbers to allow sampling, the bobcat is also sensitive to habitat fragmentation (Figures 9 in Crooks 1997). Although spotted skunks and mountain lions are more sensitive to landscape variables, their numbers are too few to allow effective monitoring. Coyotes are of intermediate sensitivity and are significantly affected only by severe habitat degradation.

Comparison of Study Methods

Scat collection is the most effective sampling method in terms of time, materials and training invested. Although some training in scat identification is necessary, samples can always be referred to a biologist. While only minimal training is necessary to use cameras, startup costs and the high rate of vandalism warrant their use only in cases where an identification needs to be verified or only in remote locations. Tracking surveys demand a relatively more skilled researcher, setup time, and have intermediate costs. The value of public observations is unclear. Although Crooks’ questionnaires for this study showed that the residents adjacent to the Extension had a surprisingly good grasp of what species were present in their backyard (Figures 4 in Crooks 1997), it has yet to be determined whether casual visitors to the Reserve have the same aptitude for species identification. Summarizing the wildlife observations recorded in the Torrey Pines State Reserve logbook, in addition to providing data sheets to new visitors, could clarify the usefulness of public identification of animals.
 

Recommendations for Predators

The following recommendations are summarized from Crooks (1997).

Corridor Preservation and Enhancement

Pacific Coast Highway

 Carmel Valley Corridor

 Sorrento Valley Corridor

Land Acquisition

Continued Monitoring

Halting Human Disturbance

Stop coyote trapping in the Reserve. As discussed above, coyotes appear to control housecat numbers in the Reserve thereby limiting killing of native rodents, birds and reptiles by domestic cats. The public appears to accept this. Although 70 percent of residents adjacent to the extension realized that coyotes attack and kill their pets, only 8 percent believed coyotes should be killed in response.

The Railroad Issue

Stacie Hathaway, an Environmental Service Intern at the Reserve documented faunal mortalities along the railroad tracks within Los Peñasquitos Lagoon. Fencing off the railroad would prohibit north-south movements within the Lagoon and does not appear to be an acceptable alternative. Raising the tracks to allow free animal movement below, and decreasing speeds within the Reserve are two potential solutions suggested by Robert Fisher (personal communication, 1997).

Public Education

Make patrols into areas of the Reserve less frequented by park staff. Staff patrols tend to focus on areas accessible by vehicle or footpaths in the Main Reserve (Beach Trails, Guy Fleming, Parry Grove, and along the Carmel Valley Road). Many other areas are more rarely patrolled, specifically: all of the Lagoon, the Broken Hills area, west of the Torrey Pines Golf course and the Extension. Removal of wildlife and soil, off-trail hiking, mountain bike riding, trampling sensitive vegetation, dogs running unleashed in the Extension, and introduction of exotic seeds to feed the birds are all frequent occurrences (personal observation).

REPTILE AND AMPHIBIAN SURVEY

Reptiles and amphibians are collectively referred to as herpetofauna. Herpetofauna were chosen as a focus for this study because of a lack of baseline data regarding the species inhabiting the Reserve. In addition, species of federal and/or state concern were known to occur in habitat similar to that found at Torrey Pines. As discussed earlier, sensitive or rare species are more susceptible to the effects of habitat fragmentation and degradation by virtue of their already reduced population size. Given the relatively reduced mobility of these taxa as compared to larger vertebrates and birds, they provide another important level of information for studying the effects of habitat fragmentation and degradation on faunal diversity.Over a two-year period, Robert Fisher and Ted Case surveyed herpetofauna of Torrey Pines State Reserve as part of a larger, multi-county study in Southern California (Fisher and Case 1997). This survey provided important baseline data regarding the current status of these taxa within the Reserve and made recommendations for future management practices. As a side note to their primary project, some general trends in rodent presence/absence, as well as activity patterns were noted. The following is summarized from their 1997 report.

Materials and Methods

Between 1995 and the present, 35 sites were sampled for the presence of reptiles and amphibians at the Reserve. Sites were distributed across the primary habitat types: shrub dominated Southern Maritime Chaparral (chaparral), sub-shrub dominated Southern Maritime Chaparral (coastal sage scrub), and Torrey Pines Forest. At each site an array consisting of seven 5-gallon buckets functioning as pit fall traps connected by drift fences were used (for specifics, see Fisher and Case 1997). In addition, hardware cloth funnels were used to capture large snakes and lizards, and a plywood board along each array arm was employed to detect tracks of California Legless Lizard. Animals captured were marked (by toe-clipping or scale-clipping) then released after being weighed and measured.The Reserve was divided into three areas for sampling: Broken Hills, Lagoon/Guy Fleming Trail/Parry Grove and the Extension. Samples were taken for 10 consecutive days every 6 weeks, for a total of 50 to 60 days a year, spread evenly across all seasons. Figures 4.1 and 4.2 are orthophotographs showing the locations of the trapping arrays. Figures 4.3 and 4.4 show the location of the arrays relative to mapped habitat associations. (See Section 2 for descriptions of the habitat classes).

Results of the Herpetofauna Survey

Species Present

Twenty-one species and over 1,500 specimens representing 10 herpetofaunal families were documented during the duration of this study (Table 1 of Fisher and Case 1997). Only Crotalus ruber and Anniella pulchra were not captured, although the former was seen in the east Lagoon by Mike Wells, and the latter was detected at the arrays by the distinctive trail it leaves. Of the 21 species captured (or observed), 8 are listed or have become candidates for federal endangered species status or are currently listed as California Species of Special Concern by California Department of Fish and Game. The sensitive species found in the Reserve between 1995-1997 are the following:   Coast Horned Lizard (Phrynosoma coronatum)

Coastal Western Whiptail (Cnemidophorus tigris)

Orange-Throated Whiptail (Cnemidophorus hyperythrus)

Coronado Skink (Eumeces skiltonianus)

California Legless Lizard (Anniella pulchra)

San Diego Ring-Necked Snake (Diadophis punctatus)

Two-Striped Garter Snake (Thamnophis hammondii)

Red Diamond Rattlesnake (Crotalus ruber)

Diversity

Site diversity ranged from 5-11 species per sampling site (Figures 2a and 2b of Fisher and Case 1997). No general pattern was obvious. Sites with the largest number of species do not necessarily have the most sensitive species (Figures 3a and 3b of Fisher and Case 1997). Although Lagoon sites did not show high diversity, three species were found there that were not recorded elsewhere in the park;: western toad (Bufo boreas), western yellow-bellied racer (Coluber constrictor), and two striped garter snake (Thamnophis hammondii).

Distribution and Sensitivity

Overall, herpetofaunal distributions appeared to be influenced by gross separation of areas by topography and urbanization rather than vegetation. Some species, however, are exceptions (see species descriptions).Nine of the nineteen species captured occur within all three Torrey Pines areas and six of these are sufficiently widespread within sites to probably not be of any immediate management concern.Seven species have a more tenuous existence, as they occur at only two of the three Torrey Pines areas (Table 1 of Fisher and Case 1997). Since these 7 species are not widespread within their sites of occurrence, they may be at a higher risk of extinction within the Reserve.Three species occurred at only one site within the Lagoon area and another three occur only at the lagoon and one other site. The restriction of these rare species to the areas adjacent to the lagoon underscores the importance of this habitat to overall herpetofaunal diversity. The relatively limited public access (and thus disturbance), insulation from roads because of slopes (with the exception of the western edge), and connectivity to more eastern areas may be positive features in the Lagoon benefiting the survival of these species.

Status of Sensitive Snakes and Lizards

Due to their sensitive status, the following ten species of snakes and lizards are discussed in detail below. As species whose requirements appear to be more stringent than other reptiles in the community, the species present in Torrey Pines should be used as a focus for reserve management. Life history and distribution of these species, in addition to specific management recommendations, are detailed below.
 

Coast Horned Lizard (Phrynosoma coronatum)

Radiotracking data of P. coronatum in the Extension (Suarez and Richmond unpublished data) suggests that this species is isolated into two subpopulations, likely increasing each subpopulation’s probability of extinction (Figure 5 of Fisher and Case 1997). Runoff from urban areas adjacent to the mesa appears to be silting in some of the habitat (Point A on Figure 5), including the area around the endangered Dudleya brevifolia population. Fisher and Case suggest that the runoff may benefit the introduced Argentine ant, which may adversely affect P. coronatum by displacing the horned lizard’s preferred food source (Suarez in press, King in prep, Richmond and Suarez unpublished data). 2) Reintroduce P. coronatum into the Parry Grove area. This area is ideal for reintroduction as it appears free from the Argentine ants (King in prep.), and is naturally isolated from encroachment. The habitat is appropriate, and the preferable food source of P. coronatum (Pogonomyrmex subnitidus) is abundant. As the area may be subject to a controlled burn in the near future, iceplant debris will be removed, exposing more sand and benefiting Coastal Horned Lizards. Since it is unlikely that these animals can disperse on their own from the Broken Hills area, specimens for introduction could be salvaged from future developments on Carmel Mountain. This is preferable to displacing individuals already present within the Reserve, because populations in the Reserve do not appear to be large enough to provide recruits.

3) Continue sampling sites for another year. The recent captures of juvenile Coastal Horned Lizards necessitate a continued study to determine their fates and thus the probability of survival of this species in the Reserve.
 

Coastal Western Whiptail (Cnemidophorus tigris multiscutatus)

• Status: Federal Candidate Species

• Distribution and Movement Patterns: This species was one of the rarest lizards recorded. Individuals moved among sites in the Broken Hills areas.

Congenerics (individuals belonging to the same genus) often compete relatively intensely with one another for resources (compared to more distantly related species for example). As a result, one might expect an inverse relation to exist between the presence of the two sensitive species C. tigris and C. hyperythrus at sampling sites. This trend was not found, and their respective highest densities occurred at different areas within the reserve (Figure 6 of Fisher and Case 1997).

There appear to be two separate populations of C. tigris. The first is adjacent to the lagoon and the second is found within the Broken Hills area. The lagoon population may be connected to other populations along the eastern slope of the park. Fisher and Case (1997) suggest that due to its potential link with other areas of the Reserve, the lagoon population may have a better chance at long-term viability compared to the population in the Broken Hills area.

• Reproduction: Compared to other sampling areas in Southern California, there appears to be a dearth of juvenile coastal western whiptails at Torrey Pines (Figure 7 of Fisher and Case 1997). Juveniles were caught for the first time in August 1997. Fisher and Case (1997) believe this may indicate a reproductive problem in this population. In May-July 1997, coastal western whiptails were captured at four sites within the lagoon. This species was not recorded in the lagoon the previous year. The authors believe the distribution numbers show that the lagoon population may have a better chance at long-term viability than those of other areas.

• Habitat affiliations: There are no obvious trends.

• Recommendations:
 

1) Continue sampling sites for another year. The recent captures of juvenile coastal horned lizards necessitate a continued study to determine their fates and thus the probability of survival of this species in the Reserve.  


Orange-Throated Whiptail (Cnemidophorus hyperythrus)

• Distribution and Movement Patterns: Although widespread in Baja California, this species only occurs in coastal southern California in the United States. It was the second most common lizard recorded at Torrey Pines. Although captured in all three areas, it was uncommon near the lagoon and the Guy Fleming Trail. Highest densities were found in Parry Grove, especially on the seaside slope (Figure 6 of Fisher and Case 1997).

As discussed previously, there was no relationship found between the presence and abundance of C. hyperythrus and C. tigris at sites within the Reserve.

• Reproduction: There is good evidence of reproduction and recruitment (Figure 8 of Fisher and Case 1997).

• Habitat affiliations: Fisher and Case (1997) suggest that Cnemidophorus hyperythrus may prefer sub-shrub dominated Southern Maritime Chaparral with very sandy soil as found in Parry Grove where highest densities were recorded. This site also lacks Argentine ants, and there is an abundance of downed wood which may increase availability of termites, their preferred food.

• Recommendations: This species does not currently appear at risk of extinction in the Reserve, but Fisher and Case (1997) recommend:
 

1) Monitor edge populations. Changes outside of a reserve often impact communities on the edge of reserves. Such an effect is called an "edge effect." Thus, species on or near reserve edges are often in a more precarious situation.

Coronado Skink (Eumeces skiltonianus interparietalis)

• Status: Federal Candidate Species

• Distribution and Movement Patterns: Eumeces skiltonianus was captured in all three areas within the Reserve, but at only a third of the sites (Table 1 of Fisher and Case 1997). No obvious patterns were observed.

• Reproduction: Few juvenile Coronado skinks were collected at Torrey Pines (Figure 9 of Fisher and Case 1997). Fisher and Case (1997) suggest there may be a reproductive problem in this species, similar to that observed in P. coronatum and C. hyperythrus.

• Habitat Affiliations: Sub-shrub dominated Southern Maritime Chaparral appears to be preferred. Few individuals were found in Torrey pine forest or shrub dominated Southern Maritime Chaparral.

• Recommendations: None noted.

California Legless Lizard (Anniella pulchra)

  • Status: State Species of Special Concern and Federal Candidate Species

• Distribution: Legless Lizards were never collected in buckets. Therefore, boards were left along the drift fences at each site during Spring 1997, in order to detect their distinctive undulating trail imprints. Trail imprints were found at sites in the lagoon, Parry Grove and along the Guy Fleming Trail. An individual was captured in spring of 1997, near the Extension.

• Reproduction: No information

• Habitat Affiliations: This species appears to prefer very sandy areas in the Reserve.

• Recommendations: Fisher and Case (1997) recommend the following:
 

1) Sample remediated sand dunes. As A. pulchra appears to prefer sandy areas, it may occur on remediated sand dunes. Leave out boards in this area to determine if the lizards are utilizing this habitat.

2) Continue iceplant removal, especially in areas A. pulchra is known to prefer. Iceplant is known to negatively affect invertebrate communities on sand dunes thus potentially impacting the Legless Lizard (Slobodchikoff and Doyen 1977). Iceplant removal is additionally beneficial by making more sand available thus increasing its prey density (Fisher and Case 1997).

San Diego Ring-Necked Snake (Diadophis punctatus)

  • Status: Federal Candidate Species. Historically, this was a common garden snake in San Diego, but appears to be declining due to increasing urbanization.

• Distribution: The San Diego ring-necked snake was found at three sites within the Extension, at one site in the Torrey Pines Forest on the Guy Fleming trail and at one Lagoon site. Fisher and Case describe them as very secretive most of the year, although they may be observed foraging during the day in the spring.

• Habitat Affiliations: They tend to prefer areas with increased moisture levels, including riparian zones, as indicated by their locations of capture. They feed on salamanders and small lizards.

• Recommendations: None noted.

Two-Striped Garter Snake (Thamnophis hammondii)

  • Status: State Species of Special Concern and Federal Candidate Species

• Distribution: Although once frequent road kill along Hwy 1 crossing Los Peñasquitos Lagoon, the Two-Striped Garter Snake is clearly rarer now. Two specimens were observed and one captured in July 1997.

• Habitat Affiliations: Typically T. hammondii is associated with freshwater wetlands, including vernal pools, creeks, rivers, marshes, and ponds. Very few frogs or toads, an important food source for T. hammondii, were collected within the reserve (Table 1 of Fisher and Case 1997), which may affect their abundance. Pacific tree frogs were widespread in the Broken Hills area. This could be an artifact of the increased moisture in this area due to the adjacent golf course. However, T. hammondii was not observed in this area during this study.

• Recommendations: None noted.

Red Diamond Rattlesnake (Crotalus ruber)

  • Status: Federal Candidate Species

• Distribution: Historically widespread throughout southern California, many coastal sites now lack this species. Currently, Crotalus ruber appears to be widespread only inland. Fisher and Case (1997) believe that its decline in the Reserve is likely related to the fragmentation of the Reserve by roads. This species can obtain a large size (2 meters), and is often observed as a road kill further east.

• Habitat Affiliations: Southern Maritime Chaparral

• Recommendations: Fisher and Case (1997) recommend the following:
 

1) Reintroduce specimens from Carmel Mountain or other development areas to the east to see if C. ruber could reestablished itself within the Reserve. Specimens could be obtained from the mitigation of projects east of I-5. The reintroduction of this rattlesnake should pose no additional public safety issue, as C. viridis is already widespread in TPSR, and, by Fisher’s observation, C. ruber is typically more docile

2) Construct a barrier along Torrey Pines Road on t Status: Federal Candidate Species

 

Coastal Rosy Boa (Lichanura trivirgata)

• Distribution: Slow moving, easy to identify, and a popular pet, the Coastal Rosy Boa is absent from the Reserve, likely due to road kills and collection. Historically it was found in areas around the Reserve (Klauber 1920-40s).

• Recommendations:
 

1) This snake would be difficult to reestablish because of the number of people using the Reserve and the risk of poaching. Some of the more remote canyons may afford more protection and a more thorough posting of fines for collecting in the Reserve may help limit poaching.

2) Construct drift fences along road edges to limit mortalities on roads where snakes may cross. he lagoon side to

Coastal Patch-Nosed Snake (Salvadora hexalepis virgultea)

• Status: Federal Candidate Species

• Distribution: Unclear. If it is present in the Reserve, it is likely in very low numbers. Historically, this species was found at Del Mar and Miramar in the Torrey Pines area and likely throughout the Reserve. The wide ranging behavior of this snake and the Red Racer may have made them both susceptible to extirpation in fragmented habitats.

• Habitat Affiliations: Southern Maritime Chaparral

• Recommendations: None made.
 

Historic Numbers

Based on Laurence Klauber’s research in the 1920s and 1930s on snakes and incomplete records from the San Diego Natural History Museum for areas in and around the Reserve, 12 species are believed to have potentially disappeared from the Reserve over the last century. These species are the following: Western Pond Turtle (Clemmys marmorata) -sensitive
California Red-Legged Frog (Rana aurora draytoni) -sensitive
The Western Spadefoot Toad (Scaphiopus hammondii) -sensitive
Coastal Rosy Boa (Lichanura trivirgata ) -sensitive
Coastal Patch-Nosed Snake (Salvadora hexalepsis) -sensitive
Red Diamond Rattlesnake(Crotalus ruber) -sensitive
California Glossy Snake (Arizona elegans occidentalis) -sensitive
Western Blind Snake (Leptotyphlops humilis)
Western Yellow-Bellied Racer (Coluber constrictor)
Red Racer (Masticophis flagellum)
Western Long-Nosed Snake (Rheinocheilus lecontei)
California Black-Headed Snake (Tantilla planiceps)
 

Snakes

Snakes alone have been well studied in this region. As a result, only the decrease in diversity of this group at the Reserve can be discussed with certainty. Historically, sixteen species of snakes could have occurred within the Reserve. Eight of these were captured in the pitfall arrays (Table 1 of Fisher and Case 1997) and one, Crotalus ruber was observed in the eastern Lagoon (Mike Wells, personal communication) and may have migrated or washed down from Carmel Mountain (Fisher and Case 1997). There may have been extirpation of the remaining 7 species within the reserve since Klauber’s study 70 years ago. Of the missing 8 species, only three were considered sensitive (Lichanura trivirgata, Salvadora hexalepsis, and Crotalus ruber), and they appear to be generally declining along the coast. The remaining 5 species are generally considered to be widespread throughout southern California with the exception of Arizona elegans occidentalis which appears to be extinct along the coast and may require legal protection in the future.

Lagoon Species

Because the moister, freshwater regions in the eastern Lagoon were not sampled, the presence of the following three species is not clear. Pacific Pond Turtle (Clemmys marmorata)
Western Spadefoot Toad (Scaphiopus hammondii)
California Red-legged Frog (Rana aurora draytoni )
  Fisher and Case (1997) suggest that Clemmys marmorata may still be present within the upstream channels of the Lagoon. Scaphiopus hammondii could probably persist on the reserve if there were adequate ponds for its successful reproduction. Historically, it was likely associated with the larger mesa tops to the south of the main reserve that now forms the Torrey Pines Golf Course and biotech developments. It presently occurs across the lagoon on Carmel Mountain, and may be found within the Reserve if pools result from the high rainfall predicted for 1998. Rana aurora draytoni is not believed to exist in the Reserve (Fisher personal communication).

Other Species

Historic records obtained from the Natural History Museum of San Diego suggest that an additional 8 non-snake species were found historically in areas in and around the Reserve. As common species are not represented in these records and geographic location information is sometimes too general, their use in reconstructing the historic community within the Reserve is limited. Nevertheless, a complete list of the museum’s collection would help to document the historic non-snake herpetofauna, and identify other declining species (Contact Records of Collections Section, San Diego Natural History Museum).

Activity Patterns

A very strong pattern of seasonal activity exists for the amphibians, lizards, and snakes. The months of March-May showed increased activity for all three groups and thus represents the best time for future sampling (see Fisher and Case 1997 for more detail). All groups tended to be affected by rainfall patterns. Continuing Fisher and Case’s study into 1998 would enable documentation of herpetofaunal response during an El Niño year and would better define the timing of herpetofaunal activity and their shifts due to weather patterns.

Amphibians

Amphibians are not usually active in the summer months. The Extension had the highest abundance, led by the slender salamander (Batrachoseps pacificus) (Table 1 of Fisher and Case 1997).

Lizards

Peak activity was between February and May/June in 1996 and 1997. The period of least activity is approximately September-February (Figure 11 of Fisher and Case 1997). The Extension has the greatest abundance of lizards per array (Table 1 of Fisher and Case 1997). Fisher and Case (1997) suggest that the abundance of lizards in the Extension may be related to the presence of coyotes, as they may suppress the population of lizard predators such as cats, dogs, and gray foxes.

Snakes

Activity patterns fit a very tight schedule, unlike many lizards which are active year-round. Snake activity was highest from February-July in 1996 and 1997. November-February have basically no snake activity. As the last two years had very little rainfall, it will be interesting to see if the snake activity period changes during a wet El Niño year.

Results of inadvertant rodent captures

Over 900 records of mammals representing five different families were inadvertently captured in the herpetofauna arrays. The most commonly collected species were classified within two families Cricetidae (rats and mice) and Soricidae (shrews). Over 150 shrews of both southern California species were captured in Torrey Pines.

Distribution

Mice

Mice were present at every array with the exception of the Torrey pine forest array in the extension. Capture rates for sub-shrub dominated Southern Maritime Chaparral sites were higher than at shrub dominated sites and were greatest in the Lagoon areas (Table 3 of Fisher and Case 1997).

California Meadow Vole (Microtus californicus)

Microtus californicus was most commonly captured in sub-shrub dominated Southern Maritime Chaparral in Parry Grove and was rare or absent in shrub dominated habitat, perhaps due to low densities. Microtus californicus was also frequently captured in areas of Torrey pine forest. Most of the sites where they did not occur were on Linda Vista Formation, which could be too hard for tunneling.

Shrews (Notiosorex and Sorex)

Both gray (Notiosorex crawfordi) and Ornate (Sorex ornatus) shrews were captured. Shrews were abundant at the Guy Fleming array, several Broken Hill arrays, and one lagoon site. Ornate shrews appear restricted to mesic habitats, and are not widespread throughout Fisher and Case’s southern California study sites. The Reserve appears to support the highest densities that Fisher and Case (1997) have observed.

Rodent Activity Patterns

There is no obvious period when all rodent taxa can be sampled at the peak of their activity. Further studies are needed to clarify patterns and determine the best season(s) for sampling.

Mice

Mice captures show similar seasonal trends across sites. Captures appeared to peak between January-February, however, sampling did not occur in December. Captures were lowest from April-November.

Voles

Vole captures peaked from February-March and were relatively high during their breeding season in November-May (Salvioni and Lidicker 1995 in Fisher and Case 1997). As some M. californicus populations exhibit multi-annual population cycles (Salvioni and Lidicker 1995), activity patterns are likely to vary.

Shrews

Shrew captures peaked in February-April and were lowest in September-November. Sampling did not occur in December or January. This taxon needs further study.

Areas of Special Concern

The following three areas are of importance. because they harbor sensitive species: The following seven species appear to be associated with the Lagoon: California Legless Lizard (sensitive)
Coastal Western Whiptail (sensitive)
Coronado Skink (sensitive)
San Diego Ring-Neck Snake (sensitive)
Two-Striped Garter Snake (sensitive)
Western Toad
Western Yellow-Bellied Racer This area has a high diversity of species as well as several resident sensitive species such as the Coastal Western Whiptails (C. tigris), Coastal Horned Lizards (P. coronatum) and the Night Snake (Hypsiglena torquata).

Recommendations for Herpetofauna

Fisher and Case (1997) suggest the following actions, except where noted. Additional information can be found in their report.

 Exotic Species

This widespread exotic disrupts and depresses arthropod communities (Slobodchikoff and Doyen 1977), and thus potentially affects organisms on higher trophic levels within the Reserve. Pulled ice plant should not be left in place, as it forms a humus that covers the ground and retards native plant growth (Fisher personal. observation) Widespread in all areas but Parry Grove, these ants displace native ant species (Suarez et al. in press; King in preparation), may displace other arthropods (King personal communication), and may cause a decline of the Coastal Horned Lizard, which is a native ant specialist (Suarez, personal communication). Coastal Horned lizards within the Extension appear to have shifted their diet to beetles when the exotic Argentine ants are present (Suarez et al., unpublished data). The impact of this dietary shift is unknown. Moisture levels near the golf course in Broken Hills, and near the school and houses in the Extension, as well as in the iceplant humus may play a role in Argentine ant invasion. The latter effect is unproven, however.

Fisher and Case (1997) suggest that the Argentine ant may have caused the extinction of the shrews in the Extension. Common along the southern California coast except the Extension, Fisher and Case suspect that the strong odor of the shrew which may attract an Argentine ant attack, in conjunction with the isolation of the Extension population, may have led to shrew extinction in this area.

House cats severely impact native wildlife in the Extension (Crooks, personal communication). Two individual Coastal Horned Lizards used in a radio tracking survey in the Extension were attacked by what appear to be cats (John Richmond, personal communication). Educating residents on the impacts of house cats on wildlife will help. Controlled burns might benefit the herpetofauna of the Reserve by reducing humus build-up from ice plant, and successional chaparral. Some of the sites adjacent to a past burn area in the Broken Hills area (6 and10), have high diversity and Site 10 and the highest abundance of Coastal Western Whiptails. High animal mortality occurs on the train tracks through the Lagoon (Stacie Hathaway unpublished data). Warning devices of a train’s approach may decrease mortalities. As the tracks themselves might bar herpetofauna dispersal, areas should be provided where these species could cross under them.

Physical Modifications

Fisher and Case (1997) believe that the low abundance of Pacific Tree Frogs and western toads along the lagoon indicates a lack of breeding sites for these species upstream. These areas have not been sampled or investigated, however. They recommend that the two shallow ponds at the old jeep trail crossing, along the Broken Hills Trail should be enhanced to facilitate reproduction of the low densities of tree frogs in this area. However, this action would be inconsistent with State Park natural resource management philosophies and directives, as it would be promoting an artificial situation to benefit a common widespread species.

 Enforcement

Mountain bikes frequently trespass on the South Lagoon trail and the impact is severe. Biking causes erosion, destroys native vegetation adjacent to trails and frequently kills reptiles and invertebrates. Animals have been observed along the trail killed or maimed by bikes. Trespassing is extensive in the Reserve, especially in the Extension and Broken Hills areas. Dudleya brevifolia, a sensitive species found in these locations, has been smashed at both locations (Fisher personal observation). Patrols by staff and volunteers should be coordinated.

Education

This will tear down common misconceptions about rattlesnakes and enable visitors to differentiate the southern pacific rattlesnake (C. viridis) from the rare red diamond rattlesnake (C. ruber). This would also facilitate the identification of locations where C. ruber may be present.

Corridor Creation

Fisher and Case (1997) write: Three potential corridors for herpetofauna to areas east of the Reserve exist (Fisher and Case 1997). These are: The route is from the southwestern edge of the lagoon to Los Peñasquitos Canyon Preserve and into Miramar. Pinched at I-5 and I-805, landscaping under these freeways could reduce the effective distance across these gaps. This channel might possibly serve as a corridor for some lizards and snakes if there was greater upland edge along it. Crest Canyon is the closest suitable (non-riparian) habitat for reptiles and amphibians in the Extension. Unfortunately, an urban matrix divides the two areas. Fisher and Case suggest educating residents on the "wildlife corridor" near their homes and motivate them to use of native plants for landscaping to facilitate animal movement. Posting signs on Del Mar Heights Road, designating it a wildlife crossing would decrease the abundance of road kill. Access to Crest Canyon places reptiles and amphibians in the San Dieguito drainage, but a connection to the east is still needed. Revegetation along I-5 where it crosses the valley may enable reptiles and amphibians to cross under the underpass along the river. Barriers would be necessary to ensure reptiles and amphibians do not cross the freeway.

 

AVIFAUNA SURVEYS

Introduction

Over the last three decades, twelve different avifauna surveys have been conducted within various areas of the Torrey Pines State Reserve (Table 5.1). Based on their results, we summarize the status of seven different sensitive bird species, each suspected to be resident, or at least a visitor to the Reserve. The species studied were: Belding’s Savannah Sparrow (Passerculus sandwichensis beldingi), California Least Tern (Sterna antillarum browni), Snowy Plover (Charadrius alexandrinus nivosus), Light-footed Clapper Rail (Rallus longirostris levipes), Coastal Cactus Wren (Campylorhynchus brunneicapillus), California Gnatcatcher (Polioptila californica californica), and Least Bell’s Vireo (Vireo bellii pusillus). By choosing "sensitive" species (usually listed as Endangered or Threatened at the state or federal level), we hoped that the needs of these groups which appear to have the strictest requirements for survival would function as umbrella species, and identify factors affecting more common bird groups as well.

Trends

Of the seven species surveyed, the only one with stable, healthy population density is the Belding’s Savannah Sparrow. All other species exist at very low numbers. Breeding status varies significantly between species. Nearly half of the birds studied (California Gnatcatcher, Belding’s Savannah Sparrow, Light-footed Clapper Rail) currently breed within the Reserve. Two species, the Snowy Plover and the California Least Tern have nested within the past two decades. With some planning (see below) it appears very likely that they could do so again. The Least Bell’s Vireo and the Coastal Cactus Wren are not resident in Los Peñasquitos Lagoon despite the availability of proper habitat.

Habitat Affiliations

With the exception of the California Gnatcatcher, which nests in the sub-shrub dominated Southern Maritime Chaparral, the remaining resident species nest and feed primarily within lagoon habitats. Belding’s Savannah Sparrow nests among pickleweed (Salicornia virginica) in the low marsh. Feeding occurs in all portions of the lagoon, including the beach and adjacent scrub areas. The California Least Tern has nested in "saltpannes," in this case areas that have collected large amounts of sediment. The Light-footed Clapper Rail is found in the pools of the lower marsh at the eastern end of the lagoon. Snowy Plovers seem to prefer the mudflats and coastal dune areas.

Conservation Issues

Several issues must be addressed in order to ensure the long term survival and reproduction of the five resident species. Disturbance to nesting sites is the greatest threat to all five of the resident bird species. The eastern lagoon, as well as the beach/dune areas at the mouth of the lagoon, are especially sensitive. The maintena