STATE OF CALIFORNIA
THE RESOURCES AGENCY
DEPARTMENT OF FISH AND GAME

MAMMALIAN SPECIES OF SPECIAL CONCERN IN CALIFORNIA^1/
by

Daniel F. Williams
Department of Biological Sciences
California State University, Stanislaus
Turlock, California 95380

ABSTRACT

The native species of land mammals of California which currently do not have state or federal Threatened or Endangered Species status were investigated in order to identify those potentially threatened with extinction Investigations concentrated on determining historic and current distributions, habitat associations, population status, and the nature and proximity of threats of extinction. Information was developed primarily from the literature, museum records, and field notes, and from contacts with biologists with knowledge of current developments in the field. Detailed studies were conducted in some areas, but only cursory field work was undertaken in other areas of concern. Populations of 36 species and subspecies were considered to be potentially jeopardized. These are placed in three priority categories. The 13 taxa in the Highest Priority face a high probability of extinction if current trends continue; the 1.1 taxa in the Second Priority are definitely declining in population size and appear jeopardized, but the threats are less immediate; the 12 taxa in the Third Priority appear not to face extinction soon, but their populations are declining seriously or they are otherwise highly vulnerable to human developments. Information on distribution, population status, habitat, and taxonomy, and recommendations for management actions are presented for each species on the List of Concern. Brief remarks are included for 56 other taxa considered in developing the final List of Concern.

Species limited to or primarily dependent upon riparian and wetland communities have been affected most severely by human developments. Five geographic areas of critical concern are: the Colorado River riparian corridor; the San Joaquin Valley lowlands, including grassland, riparian and wetland communities; the tidal marshes of the Los Angeles Basin; the tidal marshes of San Francisco and San Pablo bays; and the grasslands of the southern California coastal basins. Loss and fragmentation of mature and old_growth forests, lack of data on population structure of some game and fur_bearing species, and human disturbances of sensitive species are other important factors generating concerns for several species. 1/ Wildlife Management Division Administrative Report 86_l (June 1986). Supported by federal Endangered Species Act grant_in_aid funds for Nongame Bird and Mammal Section project E_W_4, IV_14.1; and by internal Nongame Bird and Mammal Section research funds.

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RECOMMENDATIONS

In addition to recommendations contained in the species accounts for the preservation of California's mammals, the California Department of Fish and Game and I recommend the following:

1. Give high priority to the preservation and/or restoration of plant communities essential to wildlife:
   1. Restore and protect riparian forests and wetlands in California, with special attention to those of the Colorado River and the San Joaquin Valley.
   2. Restore and protect tidal wetlands, especially those in San Francisco, San Pablo, and Suisun bays and those along the southern California coast in Ventura, Los Angeles, and Orange counties.
   3. Preserve and protect native grasslands and desert shrub communities in the San Joaquin Valley, Salinas Valley, and the southern California coastal basins in Los Angeles, Orange, Riverside, and San Diego counties.
   4. Preserve and protect mature and old_growth conifer forests in blocks large enough to support species such as Fishers.
   
   
2. Propose species on the List of Special Concern that meet the criteria of Threatened or Endangered Species to the California Fish and Game Commission and the U.S. Fish and Wildlife Service for addition to the lists of Threatened and Endangered Wildlife.
3. Initiate programs to determine the effects of hunting and trapping on game and forbearing species on the List of Special Concern and modify regulations as appropriate.
4. Encourage the protection of all species of bats in California and initiate an educational program to inform the public of the role of bats in control of insects and the sensitivity of bats to disturbance in maternity roosts and hibernacula. Support and assist the development of regulations prohibiting the poisoning or killing of bats as control measures in human structures.
5. Encourage governmental, educational, and conservation agencies and institutions involved in wildlife, land, and resource management to give high priority to Species of Special Concern in research programs and land and resource management decisions.
6. Encourage persons with information on Species of Special Concern or other species that may be threatened to bring the information to the attention of the Department of Fish and Game. Revise the List of Special concern every two years to reflect current information on distribution, population status, and management recommendations.

PREFACE

The primary objectives in preparing this document were to identify taxa of mammals in California that had no status as Endangered, Threatened, or Fully_protected, but which appeared to be vulnerable to extinction, and to develop a set of priorities for determining their status and ensuring their survival. As originally conceived and implemented, the project provided no resources for field investigations, although most areas of the state were visited and limited field work was conducted. In the ensuing five years, however, opportunities to conduct more extensive field work in several areas have arisen and the investigations have resulted in removing several species from the draft List of Concern, moving others to lower categories, and elevating others to higher categories. Three species included on the final list were not investigated in the same detail as others, because in the early stages of the project I had decided there were no indications that they were in jeopardy. Subsequent to preparation of the draft final report, however, reconsideration of their status has resulted in their inclusion. I thought it better to include them with only partial data available rather than to delay the preparation of the final report.

A rough draft of the accounts of 52 species and subspecies to be included in this report was prepared and submitted for comment to the California Department of Fish and Came in 1981. A completed draft of the report was submitted later in 1981. The Department of Fish and Game finished its review and returned the draft to me for final revisions in June, 1984. By the time it was returned, considerable new information had been gathered for several species, and substantial revisions were envisioned; in addition, I had incurred a number of commitments that precluded work on the document until fall of 1985. In the interest of making the information that was gathered for the original report available, I have decided reluctantly to forego major revisions. Most sections of the report have been reorganized, 18 species have been deleted from the List of Concern (they are discussed in the section entitled "other candidate species"), three species have been added to the list of concern, and some new information, gathered during subsequent field work by me and others, has been incorporated.

23 February 1986
Turlock, California

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TABLE OF CONTENTS

Introduction

• Table I _ Extinct, Threatened, and Endangered species

• Table 2 _ Mammalian species of special concern in California
• Table 3 _ Distribution, habitat, and cause for concern
• 10 Table 4 _ Occurrence of species of concern on public lands
• Species Accounts
  • Highest Priority List
  • Second Priority List
  • Third Priority List
  • Other Candidate Species
• Table 5 _ List of other candidate species

INTRODUCTION

During the past 150 years, 515 species and subspecies of native land mammals have been recorded as occurring in California (Hall, 1981; Williams, 1984), a number much greater than in any comparable political unit north of the American tropics. Seven species, including the Mexican Jaguar (Felis onca arizonensis), Plains Bison (Bison bison bison), Gray Wolf (Canis lupus fuscus and C. l. youngi), California Grizzly Bear (Ursus arctos californicus; taxonomy of Hall, 1984), and the Western White_tailed Deer (Odocoileus virginianus ochrourus), are now extinct or extirpated within California. Coues' White_tailed Deer (0. v. cousei) probably also occurred within California, occupying the riparian forests of the Colorado River floodplain. Specimens are unknown from California, although Hall (1981) listed a record from Ehrenburg, Arizona, on the Colorado River opposite California. This species was probably already rare along the Colorado River by the time rapid immigration triggered by the gold rush, and has been extinct long since. The Long_eared Kit Fox (Vulpes macrotis macrotis) was driven to extinction by humans in the southern coastal basins of California. Pronghorns (Antilocapra americana americana)have been extirpated from most of their historic range in California, in west_central and southern parts of the state; and Tule Elk (Cervus elaphus nannodes), while no longer threatened with extinction, exist only under full protection. The decline or extinction of most of these species was primarily due to persecution and/or overharvesting by humans.

Twenty_three mammalian species (29 subspecies) in California were designated as Threatened or Endangered species in 1985, including nine marine mammals. The terrestrial species are listed in Table 1, together with those known to be extinct or extirpated from the state. The principal factor jeopardizing the rodents and Kit Fox (Table 1) has been loss of habitat. Human disturbance and intrusion into their habitats have been significant factors in the decline of the Sierra Nevada Red Fox, Southern Wolverine, and the California and Peninsular Bighorn Sheep.

Twenty native game and fur_bearing species of mammals are partially protected by hunting and trapping regulations established by the California Fish and Game Commission and administered by the California Department of Fish and Game. Additionally, the Ringtall (Bassariscus astutus), Fisher (Martes pennanti , and Northern Flying Squirrel (Glaucomys sabrinus) are protected through legislative action or by the California Fish and Game Commission. The White_eared Pocket Mouse (Perognathus alicola), Point Arena Mountain Beaver (Aplodontia rufa nigra), Point Reyes Mountain Beaver (A. r. phaea), and all species of bats are partly protected from taking through restrictions on scientific collection by the California Department of Fish and Game. The Mountain Lion (Felis concolor) is designated as a game species but presently there is no open hunting season.

All other terrestrial species of mammals in California have little or no protection, and for those and many game, fur_bearing, fully_protected, and state Endangered and Threatened species, no management plans are in operation to ensure the preservation of unique populations. Yet, the California Endangered Species Act of 1970 and subsequent

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CALIFORNIA DEPARTMENT OF FISH AND GAME

amendments mandate the preservation of all species of native mammals. Rapid agricultural development and urbanization of vast areas in California have profoundly diminished the extent of several biotic communities and jeopardized their unique biotas. For example, the floor of the San Joaquin Valley measures approximately 3.44 million hectares (8.5 million acres). Major plant communities once included valley grassland (dominated by perennial species such as Stipa pulchra and S. cernua), San Joaquin saltbush (dominated by several xeric_adapted and halophytic shrubs, including Atriplex spp., Suaeda fruticosa, Allenrolfea occidentalis, and Ephedra californica), tule marsh (dominated by species of Scirpus and Typha) , and riparian forests and savannas (Kuchler, 1977). By 1979, nearly all of this land was developed, either as large urban areas or as cultivated crop land. Less than 60,700 hectares (150,000 acres) were uncultivated, and significant portions of this latter amount were developed for petroleum extraction, strip_mined for gypsum and clay, or occupied by roads, canals, air strips, cities, oil_storage facilities, pipelines, and evaporation and percolation basins. The vast tule marshes were nearly gone; most of those that remained were degraded by seasonal flooding with waters laden with metallic salts drained from irrigated fields. The grassland communities were reduced to small remnants, mostly fringing the valley floor, and their perennial species were largely replaced by exotic species of weedy annuals such as Bromus spp., Avena spp., and Erodium spp. Of the original 404,700 hectares (about I million acres) or more of riparian communities in the Central Valley, less than 10% existed in 1979 (Warner, 1979); much of that was significantly degraded in quality.

Populations of mammals native to the arid coastal basins of southern California have been reduced drastically in size as a result of habitat loss. Today, nearly all of the populations of species native to the plant communities on the floor of the southern coastal basins face proximate threats of extinction. The Long_eared Kit Fox succumbed to the pressure of increasing numbers of people in southern California several decades ago (Waithman and Roest, 1977). Other species extirpated there and/or throughout southern California include the Mexican Jaguar (Merriam, 1919; Strong, 1926), Great Basin Gray Wolf (Grinnell et al., 1937), Pronghorn (McLean, 1944), and Coues' White_tailed Deer.

Populations of mammalian species dependent upon freshwater and tidewater riparian and wetland communities have declined markedly in nearly every region within California as a result of loss and degradation of their habitats. White_tailed Deer, dependent upon riparian communities in California, have already been extirpated (see section on Other Candidates in Results section) and several other species are seriously jeopardized.

The rapid, widespread loss of old_growth forests by logging activities raises concerns that cannot be resolved with existing information. Although no mammalian species In California is known to be limited to old_growth forests, a few require extensive tracts of relatively undisturbed forest. Fragmentation and isolation of relatively small blocks of mature and old_growth stands of Yellow Pine, Douglas Fir, Mixed Conifer, and Red Fir by recent forest_management practices has been extensive and could prove to be disastrous for wide_ranging species such as the Fisher and Marten, and for species with limited vagility such as

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1986 _ MAMMALIAN SPECIES OF SPECIAL CONCERN _

Table 1. Extinct, Threatened, and Endangered species of land mammals in California as of January, 1986. CE - California Endangered; CT- California Threatened; FE _ Federal Endangered; FT- Federal Threatened.

CALIFORNIA DEPARTMENT OF FISH AND GAME

Red Tree Mice. Likewise, some species of bats may depend on roosting sites under loose bark and in hollow cavities of standing trees and foraging sites within the forest, and their populations may be significantly impacted by loss of old_growth forests and current forest_management activities

Concern over the rapid loss of major biotic communities within California and the increasing threats to several species of mammals prompted the Nongame Bird and Mammal Section of the California Department of Fish and Game to initiate this study of potentially threatened species of mammals. The principal objectives were to identify potentially jeopardized populations of mammals within California, and to group them into priority categories for management actions, including proposals for protected status, expenditure of research funds, and preservation of essential habitat.

1986        _ MAMMALIAN SPECIES OF SPECIAL CONCERN -

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METHODS

Investigations of potentially threatened mammals were limited to taxa without Threatened or Endangered status at the state or federal level. Taxa concurrently being investigated through other projects of the Department of Fish and Game also were excluded from detailed studies

(i.e., some subspecies of the Bobcat, Felis [Lynx] rufus, and the River Otter, Lutra canadensis).

Priorities for the investigations were:

1. species endemic to California;
2. subspecies endemic to California;
3. species and subspecies whose geographic ranges extend beyond California and which appear to be jeopardized throughout their geographic range;
4. populations of taxa threatened within California but which also occur elsewhere and appear not to be threatened throughout their geographic range (e.g., Myotis velifer velifer, the Cave Myotis).

These priorities had some influence on which taxa received greatest consideration for inclusion in detailed investigations. Priority rankings, however, were based solely on the apparent proximity and nature of threats to populations. Locally depleted populations of wider_ranging taxa within California were not studied in detail, with the exception of the American Badger (Taxidea taxus).

A working list of 86 candidate species was assembled first and then information for each candidate was gathered. Blair Csuti (The Nature Conservancy) nominated some of the candidates. Data on life histories, habitat associations, historic and current distributions, systematic status, population status, and nature of potential threats were sought for each candidate. Initially, information was gathered without benefit of field work, being derived instead from published sources, other biologists, and previous field experiences in California. The intent was to develop information needed to direct limited funds for field investigations to studies of biotic communities and taxa with the greatest perceived threats to their existence. During the course of the original investigation, however, most areas in the state where loss of habitat posed a threat to one or more species of mammals were visited. Only cursory field studies were carried out, however, as time and funding did not permit detailed field work. Subsequently, more detailed studies have been conducted in the San Joaquin Valley (Williams, 1985; Glenn Basey, unpubl. ms.; Cheryl Johnson, unpubl. ms.); San Bernardino Mountains (Sulentich, 1983; Williams, 1983);) San Gabriel mountains (Williams, 1983); Tehachapi Mountains (Sulentich, 1983); east_central slope of the Sierra Nevada (Williams, 1984); western slope of the central Sierra Nevada (unpubl. data); San Pablo and Suisun bay marshes (K. Ford, unpubl. data; Williams, 1983); Point Arena area, Mendocino Co. (Dale Steele, unpubl. data); San Francisco Bay (Ford, 1986); San Pablo Creek Marsh (by Foreman; T. Rado, pers. comm.); and on Santa Catalina Island (Collins and Martin, 1985; Williams, 1983). For the majority of the species included here, however, there have been no recent, detailed, field studies undertaken.

Letters and questionnaires seeking information on potentially threatened taxa of mammals were sent to all members of the American Society of populations

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CALIFORNIA DEPARTMENT OF FISH AND CAME

Mammalogists with mailing addresses in California, and to other, selected persons in state and federal agencies, colleges and universities, and natural history museums. Approximately 500 persons were contacted in this manner. Sixteen persons responded to the request for information, and collectively listed 16 species they believed should be investigated. Of the 16, two were species of marine mammals which were not included in this project, and four were species already with state Rare or Endangered status. All of the remainder were already on the working list. Subsequent to development of the draft report, questions regarding the status of 11 other taxa were raised by Ronald Nowak (Endangered Species Office, U.S. Fish and Wildlife Service). Little additional research was conducted on most of the latter species; reasons for excluding them and other candidate species are given in brief accounts (see section on Other Candidate Species).

Information on the distributions of species on the working lists was developed from the literature and from museum records. No attempt was made to locate all records, although literature and museum surveys were as complete as time and resources permitted. Data on historic distributions were assembled from these sources, but for most taxa no detailed field surveys had been conducted prior to wide spread human developments; thus, the historical distribution records of most species are scanty. Because the investigations included a large number of taxa, and because many museums do not catalog specimens by subspecies, it would have been unreasonable to ask personnel at most museums to furnish the required information. Instead,, I visited and obtained distributional data from 13 major natural history museums and acquired information from nine others through correspondence (listed in the Appendix). Additional data from other mammal collections were obtained from the card files at the National Museum of Natural History, where for several decades early in the century the staff recorded specimens known to be housed in other museums. I also contacted several persons directly to inquire about specific taxa and human developments affecting plant communities in selected areas of California. This approach was more productive than broadcasting appeals for input. Unfortunately, however, identifying persons with the information needed was often impractical.

The species accounts in the Results section are arranged in groups by priority category and, within groups, systematically by genera, following Hall (1981). Species and subspecies are arranged alphabetically within genera. Records of distribution are listed alphabetically by county and, within counties, by locality with respect to reference point (e.g., city or physiographic feature). Localities using the same reference point are arranged by compass direction, starting with north and proceeding clockwise. Localities are listed as recorded on specimen tags and in museum catalogs or in the literature. The number of specimens, when known, and the museum of deposition or literature citation conclude each locality record. Cases where localities or identification of specimens seemed erroneous are discussed in the Remarks section.

Statements about habitat associations and population status are necessarily brief for most taxa because of lack of detailed information. Whenever possible, statements were developed primarily from information based on studies of the populations of concern rather than from studies conducted elsewhere. To extrapolate extensively from studies based on outside the area of concern carries a high risk of incorrectly characterizing

1986      _ MAMMALIAN SPECIES OF SPECIAL CONCERN _

habitat use and population biology. Comments in the Recommendation sections are suggestions for priority actions and are neither detailed nor complete. Remarks on systematic status are intended to flag potential problems which should be considered in designing studies to elucidate the status of populations. Although neither state nor federal regulations require that a jeopardized population have unique taxonomic identity to be designated Rare, Threatened, or Endangered, the political conflict resulting from unresolved taxonomic controversies involving endangered species is best avoided whenever possible.

In interpreting and compiling the information in this report, and in assigning taxa to priority categories, my philosophy has been to give the benefit of doubt to the species under consideration. I have attempted to convey the essence of available information, but time and resources did not permit detailed field investigations or development of lengthy species accounts. A principal purpose of this report is to stimulate others with information to come forward. I have not cited all of the relevant literature for most taxa, especially reports that added no new information on the limited set of topics included in the accounts.

Scientific names for species are those listed by Jones et al. (1982) unless noted otherwise in the species accounts. Common names are from Grinnell (1933) and Williams (1979), or are ones commonly used by the Department of Fish and Game. Common names for subspecies are generally unnecessary, but, because subspecies can be accorded Threatened or Endangered status under both state and federal regulations, use of common names for subspecies is necessary in this report. Names for subspecies are from the list of Grinnell (1933), but often amended to reflect current taxonomy or to shorten needlessly long names. I coined common names or adopted those of other authors for subspecies not listed by Grinnell (1933). Scientific names for subspecies are from Hall (1981) except in cases where I disagree with his taxonomy or when more recent publications have altered his taxonomic arrangements. Departures from Hall's (1981) subspecies taxonomy are noted in the species accounts.

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CALIFORNIA DEPARTMENT OF FISH AND GAME

RESULTS

Of the species and subspecies investigated for this report, 36 warrant greatest concerns. These are listed in Table 2 in three categories: Highest, Second, and Third priorities. The definitions for these categories are based on the perceived proximity of threats of extinction. Species listed in the Highest Priority category appear to face a high probability of extinction or extirpation from their entire geographic range in California if current trends continue. Populations of species in the Second Priority category are definitely jeopardized and declining, but the threats of extinction or extirpation appear less imminent. Populations of species listed in the Third Priority category appear not to face extinction in the near future, but they are declining seriously or are otherwise highly vulnerable to extirpation because of human developments, and require special attention in land_ and resource_ management decisions. Some species listed in the Second and Third Priority categories are relatively rare and virtually no current data on their distributions and population status are available; when investigated in detail, some of these may be found to face greater or lesser threats. Accounts of species included in the three priority categories are presented in the following section.

Other species investigated, but considered to warrant lesser concerns are listed in the fourth group, entitled Other Candidates, beginning on page 73. Brief remarks on the probable status of these species, deleted from the final List of Concern, are included. Lack of information for some species listed is cause for concern about their status; their deletion from the final List of Concern here should not be construed as a definitive indication of their population status.

Major contributing factors in jeopardizing most species on the List of Concern are the diminishment and degradation of natural communities (Table 3 and Species Accounts). Loss of native plant communities in four regions of California present the most acute problems threatening unique (i.e., taxonomically recognized) populations of mammals: the Colorado River riparian communities; the southern California coastal basins from the San Fernando Valley southward to the Mexican boundary, including lowland grassland and desert communities and tidal marshes along the south coast; the San Joaquin Valley desert, grassland, and riparian and wetland communities; and the tidal marsh communities of San Francisco and San Pablo bays. Loss of riparian and wetland communities is no less serious elsewhere, but fewer unique taxa of mammals are threatened. In addition to loss of habitat, disturbances by humans, especially in hibernacula and maternity roosts is perceived as a serious threat to most of the species of bats. Habitat degradation and lack of information on hunter take and population dynamics for use in management are viewed as potential threats to the five species of rabbits and hares, currently designated as game species, on the List of Concern. Cutting and fragmentation and isolation of blocks of mature and old_growth conifer forests pose potential threats to two species on the List of Concern.

Potential occurrences of Species of Special Concern on lands administered by several state and federal agencies are listed in Table 4. Information in Table 4 was developed from a "Federal Public Lands Responsibility Map" of California (1:7500,000 scale; 1978)

1986       _ MAMMALIAN SPECIES OF SPECIAL CONCERN

Table 2. Mammalian species of special concern in California, listed by priority categories. See text for definitions of priority categories. Page refers to starting page of species accounts.

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Table 3. Distribution, habitat, and major causes for concern for mammalian species of special concern in California. Refer to species accounts for details. CA- California; CI- Santa Cruz and Santa Rosa islands; CR_ Colorado River; des. -desert; disturb.- -human disturbances; GB_ Great Basin steppes; Mtn._ mountains; N- north; NW- Northwest; Pt. A._ Point Arena area; Pt. R._ Point Reyes area; SB- San Bernardino; SCB_ southern California coastal basins; SCM_ southern California coastal marshes; SCI_ Santa Catalina Island; SFB_ San Francisco Bay; SJV- San Joaquin Valley; SN_ Sierra Nevada; So_ southern; SPB- San Pablo Bay; SV- Salinas Valley; Tr. R._ Transverse Ranges; W_ west.

1986      MAMMALIAN SPECIES OF SPECIAL CONCERN      11

and from other sources. There is no similar, pictorial summary of state_managed lands nor a central source of information on state_owned lands. Thus, only lands managed by the California Departments of Fish and Game and Parks and Recreation are included. Information displayed in Table 4 should not be construed as indicating non_occurrence on lands administered by other governmental agencies or that other Species of Concern do not occur on lands administered by these agencies.

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Table 4. Occurrence of Mammalian Species of Special Concern In California on lands administered by selected state and federal agencies. BLM _ U.S. Bureau of Land Management (Dept. of Interior); CPR Calif. Dept. of Parks and Recreation; DFG _ Calif. Dept. of Fish and Game; DD U.S. Department of Defense; DE _ U.S. Department of Energy; FS _ U.S. Forest Service (Dept. of Agriculture); FWS _ U.S. Fish and Wildlife Service (Dept. of Interior); NPS U.S. National Park Service (Dept. of Interior). See Table 2 for scientific names.

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HIGHEST PRIORITY LIST

Buena Vista Lake Shrew
Sorex ornatus relictus

1932. Sorex ornatus relictus Grinnell, Univ. California Publ. Zool., 38:389. Type Locality: evacuated slough just outside of east side levee, Buena Vista Lake, 290 ft, Kern Co., California.

Distribution: Grinnell (1933) speculated that Buena Vista Lake Shrews once occupied the marshlands of the San Joaquin Valley floor throughout most of the Tulare Basin. He noted that by 1933, their range was much restricted because of the disappearance of lakes and sloughs.

Populations Status: Nothing is known about the current population status of the Buena Vista Lake Shrew. Nearly all of the valley floor in the Tulare Basin is now cultivated. Most of the lakes and marshes have been drained and are also cultivated. All of the Buena Vista Lake bed is cultivated, and most of the canals in the area are steep_sided and kept free of vegetation by use of herbicides. Ornate shrews (Sorex ornatus) may be extant in places such as the Kern National Wildlife Refuge, in wetlands of the Kern River percolation area, and along sloughs and canals on the valley floor leading into Goose Lake, although there are no records of shrews from any of these areas. Any extant populations found within the Tulare Basin may or may not be representative of S. o. relictus. Clark et al. (1982) used pitfall traps in an unsuccessful attempt to capture Buena Vista Lake Shrews on The Nature Conservancy Paine Wildflower Preserve and the Voice of America transmitter site west of Delano.

Habitat: Buena Vista Lake Shrews occupied marshes on the perimeter of Lake Buena Vista (Grinnell, 1932). Farther north, in the San Joaquin Basin, Ornate Shrews live in dense vegetation along streams and sloughs and around the perimeter of tule marshes (unpub. data). Presumably, Buena Vista Lake Shrews occurred in similar wetlands in the Tulare Basin.

Recommendations: A survey for Buena Vista Lake Shrews should be undertaken to establish its distribution and population status and to identify potential threats to remaining populations. Initial efforts should be concentrated around the Buena Vista Lake Aquatic Recreation Area (Lake Webb and Lake Evans), on the Kern National Wildlife Refuge, the Tule Elk Reserve, and along Buena Vista and Goose Lake sloughs. Pitfall traps are most effective for shrews (Williams and Braun, 1983), and can be left in place for extended times offsetting the extra effort required to set them.

Remarks: Notning has been recorded on this taxon since the original description. The more upland subspecies, S. o. ornatus, occupies the area surrounding the range of S. o. relictus. Ynte_rgra@dati@on probably occurred along the lower courses of the streams entering the floor of the Tulare Basin.

Distribution Records: KERN CO.: N side Buena Vista Lake, I (USNM); east side levee, 298 ft, Buena Vista Lake, 290 ft, 3 (MVZ); Buttonwillow, I (CAS).

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Suisun Shrew
Sorex ornatus sinuosus

1913. Sorex sinuosus Grinnell, Univ. California Publ. Zool., 10:181. Type Locality: Grizzly Island, Suisun Bay, Solano Co., California.
1979. Sorex ornatus sinuosus , Williams, Ann. Carnegie Mus., 48:426.

Distribution: According to Rudd (1955a), Suisun Shrews occur in the tidal marshes of the northern shores of San 'Fablo and Suisun bays, as far east as Grizzly Island and as far west as the mouth of Petaluma Creek. Brown and Rudd (1981), however, redefined the western boundary of the range as Sonoma Creek and Tubbs Island. Shrews living in the marshes as far east as Collinsville represent S. o. californicus (Williams, 1983).

Populations Status: At one time, San Pablo and Suisun bays were lined with salt and brackish water marshes., but today marshes are broken into several small, isolated units. The marshes of Suisun Bay are the most extensive, but Suisun Shrew populations there may be threatened in part by management of the marshes to favor growth of Scirpus. Present habitat is much less extensive in San Pablo Bay. Very few of the extant tidal marshes have a full profile of marshland vegetation, and few border on significant upland areas where marshland species can seek refuge from flooding. Suisun Shrews inhabit a smaller area and are more restricted in the habitats they occupy than are Salt Marsh Harvest Mice, an Endangered Species.

The population status of S. o. sinuosus was investigated during spring and summer, 1983, following a winter of record flooding in the marshes of San Pablo and Suisun bays (Williams, 1983). No live Suisun Shrews were captured on any of 34 transacts in marshes throughout the geographic range of S. o. sinuosus. One dead shrew was found, however. Subsequent surveys with Sherman live traps found one Suisun shrew in a marsh on the northern perimeter of Suisun Bay in 1985 (K. Ford, pers. comm.). The principal problem in both areas, but most acute in San Pablo Bay, is the lack of upland areas continuous with the marshes where Suisun Shrews and other terrestrial animals can refuge during times of flooding (Williams, 1983). Management of the marshes has not included refuges from flooding as a required element.

Habitat,: Suisun Shrews typically inhabit tidal marshes characterized in order of decreasing tolerance to inundation, by Spartina foliosa, Saliconria ambigua, and Grindelia cuneifolia, and brackish marshes dominated by Scirpus californicus and Typha latifolia (Rudd, 1955a). They appear to require dense, low_lying cover where invertebrates are abundant. Rudd stated that structure ("growth form") of the plant community, not species composition, was the determining factor in shrew occupancy. Driftwood and other litter above the mean high_tide line is probably essential for nesting and foraging sites. Upland habitats, continuous with the marshlands, offering sufficient cover and sources of food to sustain shrews during prolonged flooding of marshes and dikes, such as occurred during the winter of 1982_83, are also probably essential (Williams, 1983).

Recommendations: When the results of additional population surveys for Suisun Shrews are completed (U.S. Fish and Wildlife Service, in litt.),

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1986      _ MAMMALIAN SPECIES OF SPECIAL CONCERN _      15

marshland management practices and plans should be reviewed to determine their impact on populations of Suisun Shrews. Acquisition of upland areas for refuge from flooding, or creation of refuge sites on dikes above flood level will probably be required to provide suitable habitat for Suisun Shrews and other small mammals inhabiting the tidal marshes.

Remarks: Rudd (1955a) analyzed structural characters of Sorex ornatus-group shrews from the San Pablo and Suisun bays area and determined that shrews of the sinuosus type were recognizably distinct from S. o. californicus, but that spatially intermediate populations exhibited some intermediate characteristics. He thought that because the character gradients were rather abrupt, recognition of sinuosus as a species was justified. Brown (1971, and unpubi. dissert., 1970) found that S. ornatus and S. sinuosus had identical karyotypes, which differed from S. vagrans of the San Francisco Bay area. Karyotypes of shrews from populations previously thought to be S. v. vagrans or hybrids of vagrans, ornatus and sinuosus were shown to be identical to the ornatus_sinuosus karyotype. Brown and Rudd (1981) investigated the relationships of these shrews further, determining that sinuosus was best treated as a subspecies of S. ornatus, and restricting the distribution of sinuosus to an area approximately east of Sonoma Creek, but including Tubbs Island within the range of sinuosus.

The disposition of specimens referred to by Rudd (1955a) is not clear. Some of these are in the Museum of Vertebrate Zoology and others are in the collections at the University of California Davis. Differences in the locality descriptions on the specimen labels and in Rudd's (1955a) paper and differences in total numbers of specimens made it difficult to decide if these referred to the same specimens. Several specimens in museums, collected in marshes in San Pablo Bay in Sonoma County are designated as S. sinuosus, but are now considered to be S. o. californicus. Two specimens in the Museum of Vertebrate Zoology from "Solano County; Lake Chabot (seepage area below dam)" were assigned to the subspecies S. o. sinuosus. Lake Chabot is located on a golf course, west of the Solano Co. Fairgrounds. These specmiens may be S. o. californicus or S. o. sinuosus; they are not listed below.

Distribution Records:SOLANO CO.: 0.5 mi NE Cordelia Salt Marsh, 5 (MVZ); Gray Goose Duck Club, 1.5 mi SW Suisun, I (CAS); Grizzly Island, Suisun Bay, I (LACM), 20 (MVZ), 5 (UDAV), 2 (USNM), 19 (Rudd, 1955a); Grizzly Island, State Dept. of Fish and Game headquarters, 1 (CSCS); Honker Gun Club, near Dutton, Van Sickle Island, 1 (CAS); 3 mi E Mare Island Bridge, adjacent to White Slough and Hwy. 37, 1 (MVZ); 2.7 mi W jct. Napa Road and Hwy. 37 (on 37), 1 (MVZ); 8 mi N Rio Vista, 80 ft, 1 (CSUF); Sears Point Road, 6 mi NW Vallejo, 65 (MVZ); Sears Point Road, 8 mi NW Vallejo, 7 (MVZ); Sears Point Road, San Pablo Bay, 47 (Rudd, 1955a); South Hampton Bay, near Solano Co. public dump, 15 (MVZ); South Hampton Bay, 13 (Rudd, 1955a); Suisun City, salt marsh adjacent to Cordelia St., 4 (MVZ); Suisun marshes, periphery of Grizzly Island, 13 (Rudd, 1955a); 3 mi NW Vallejo, 1 (UDAV); Van Sickle Island, 1 mi S Dutton, 1 (CAS); Van Sickle Island, I (CAS), 3 (UDAV).

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Santa Catalina Shrew
Sorex ornatus willetti

1941. Sorex willetti von Bloeker, Bull. So. California Acad. Sci., 40:163. Type Locality: Avalon Canyon, Santa Catalina Island, Los Angeles Co., California.
1967. Sorex ornatus willetti, von Bloeker, Proc. Symposium Biol. California Islands, p. 246.

Distribution: Santa Catalina Shrews are known only from Santa Catalina Island, Los Angeles California (Williams, 1983). The localities for the specimens and, three sight records collectively span the length of the island (Collins and Martin, 1985; Williams, 1983).

Population Status: Only a single Santa Catalina Shrew was captured in a survey during January, 1983 employing pitfalls on 22 10_trap transacts distributed in all major plant communities on the island (Williams,1983). A subsequent survey, during summer, 1985, employing pitfalls on 25 10_trap transacts failed to capture any additional shrews (Collins and Martin, 1985). Williams believed that the Santa Catalina Shrew might have been on the verge of extinction. Degradation of woodland, riparian, and wetland communities by introduced ungulates, especially sheep, cattle, feral goats and wild pigs, and further degradation of these communities by diversion of water from springs and streams to the urbanized areas on the island probably were factors contributing to the scarcity of shrews. Another important factor was probably the marginal suitability of the island communities for shrews. Santa Catalina Island contains only a few small, degraded riparian communities and wetlands. Another important element threatening shrews was the high density of feral cats on the island.

Although most of the island is being managed by the Santa Catalina Island Conservancy with the objective of preserving the native biota, the Conservancy presently derives significant income from commercial hunting of wild pigs, goats, and deer, and sale of some bison. Free roaming ungulates on the island are the major threat to its native biota and a potential source of irreconcilable conflict of management objectives. These ungulates and introduced blackbuck (Antilope cervicapra) are noticeably degrading some natural plant communities and preventing others from recovering from damage caused when densities of domestic and feral ungulates were greater. Wild pigs are causing the most apparent damage in wetlands and streamside communities and on wooded slopes with deep layers of leaf litter: areas likely to be of major importance to shrews. Additional serious threats stem from the growing human resident and transient populations on the island where potable water supplies are already overtaxed. Diversion of increasing amounts of fresh water for human use will probably result in additional degradation of the already damaged riparian systems on the island.

Habitat: Although on the mainland, Ornate Shrews are often captured in upland plant associations such as coastal sagebrush and chaparral, their precise habitat requirements are unknown, and it has not been shown that communities such as these are important to breeding populations. Over most of their range in California, Ornate Shrews are most abundant in riparian and wetland communities (Collins and Martin, 1986
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1985; Owen and Hoffmann, 1983; Williams, 1983). The only specimen of S. o. willetti trapped was taken In a tangle of driftwood and woody roots_a few feet above a creek bed; riparian vegetation was poorly developed along that portion of the creek (Williams, 1983).

Recommendations: Two recent surveys for Santa Catalina Shrews have shown the extreme rarity of this insular population, but have failed to delineate critical elements of the biotic communities that must be protected in order to ensure survival of Santa Catalina Shrews. Thus, any activities taken to help protect the population possibly could have the opposite effect. Specific actions to enhance habitat for shrews on the island should only be made after obtaining results from detailed studies of Ornate Shrews on the mainland in similar communities with a similar climate. Studies should be designed to provide information needed in determining the best course of action to enhance the chances of survival of Santa Catalina Shrews. Regardless of these studies, however, preserving wetland and riparian systems should be given high priority in management of the island. Elimination of all ungulates, starting with wild pigs, feral goats, and bison would remove the greatest sources of damage to plant communities on the island. An intensive campaign to reduce the size of the population of feral cats would alleviate some pressure on shrews, but both the practicality of such a campaign and its importance in protecting shrews is in doubt.

The possibility that insular populations of Ornate Shrews occur on Santa Cruz, Santa Rosa, San Miguel, and/or San Clemente islands should not be overlooked (von Bloeker, 1967; Walker, 1980).

Remarks: The Santa Catalina Shrew was described as a species, but later was relegated to subspecific status under Sorex ornatus (von Bloeker, 1967). It differs from mainland shrews of the ornatus group in being larger and somewhat darker in color dorsally, with lighter_colored underparts. Present data are insufficient to determine the degree of relationship between Ornate and Santa Catalina Shrews, although available evidence supports treating it as a subspecies of S. ornatus (unpubl. data). A single, subfossil cranium of Sorex was found among midden remains in a rock fissure on the coast of San Miguel Island, Santa Barbara Co. (Walker, 1980). This specimen appeared to be structurally similar to S. o. willetti, according to Walker (1980).

Anecdotal accounts of sight records of Santa Catalina Shrews by residents of the island are: Middle Canyon W of Thompson Dam (Williams, 1983); Bunk House at Middle Ranch, Middle Canyon; and Road to west end, 0.2 mi W Isthmus Dump (Collins and Martin, 1985).

Distribution Records:LOS ANGELES CO.: Avalon Canyon, Santa Catalina Island, 1 (LACM); 0.1 mi W Cottonwood Reservoir, Cottonwood Canyon, 76 m, 1 (CM).

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Salt Marsh Wandering Shrew
Sorex vagrans halicoetes

1913. Sorex halicoetes Grinnell, Univ. California Publ. Zool., 10:183.
Type Locality: salt marsh near Palo Alto, Santa Clara Co., California.

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1928. Sorex vagrans halicoetes , Jackson, N. Amer. Fauna, 51:108.

Distribution: Sorex v. halicoetes is limited to the salt marshes of the south arm of San Francisco Bay (Findley, 1955).

Populations Status: Johnston and Rudd (1957) reported fluctuations in relative numbers between 1951 and 1955, based upon numbers of active nests found. They determined that Salt Marsh Wandering Shrews represented about 10% of the small mammal community of the marshes and were less abundant than Mus musculus, Reithrodontomys raviventris, Rattus norvegicus, and Microtus californicus.

Most of the once_extensive salt marshes of San Francisco Bay have been lost by human developments. The extent of remaining habitat for these shrews is small. Because they use only a limited area within the marshes, there is less habitat for them than for Salt Marsh Harvest Mice. Therefore, S. v. halicoetes may be under greater threats of extinction than the Endangered Salt Marsh Harvest Mice. Ford (1986) found 16 live Salt Marsh Wandering Shrews in a population survey of marshes in San Francisco Bay during 1985. He recommended federal Endangered Species status for S. v. halicoetes.

Habitat: Johnston and Rudd (1957) provided a detailed sketch of the habitat of Salt Marsh Wandering Shrews. The shrews frequented areas in tidal marshes that provide dense cover, abundant food (primarily invertebrates), suitable nesting sites, and fairly continuous ground moisture. Their center of activity was in the "medium high marsh," about 6 to 8 ft above sea level, and in lower_lying marsh not regularly inundated. Suitable sites were characterized by abundant driftwood and other debris scattered among Salicornia. The Salicornia was usually 1 to 2 ft tall. The detritus preserved moisture and offered refuge in dry periods to amphipods, isopods, and other invertebrates, and resting sites for shrews. Nesting material consisted of plant parts, primarily Spartina duff. The higher_lying marsh, 8 to 9 ft in elevation, was too dry and offered only minimal cover _ few or no shrews occupied this zone. The lower zone, dominated by Spartina, was subjected to daily tidal floods and had cover too sparse for shrews.

Recommendations: Any planned developments or activities that would modify marsh vegetation and degree of inundation with the range of the Salt Marsh Wandering Shrew should be reviewed to determine impact on this species. The feasibility of modification of extant marshes to enhance suitability for Salt Marsh Wandering Shrews, Salt Marsh Harvest Mice, and other jeopardized species should be Investigated.

Remarks:The taxonomy of the Sorex vagrans species group has had a complex and confusing history and additional changes in scientific names will probably be required when relationships among populations are finally resolved (Findley, 1955; Hennings and Hoffmann, 1977; Rudd, 1955a). There appears to be no controversy about the taxonomic status of the halicoetes population, however. Brown (1974) found that the karyotype of one Salt Marsh Wandering Shrew was similar to those of three specimens of S. v. vagrans from the northern part of the San Francisco Bay region. these karyotypes were most similar to S. vagrans from areas farther north in California and Oregon. Eight specimens identified as S. v. halicoetes in the collection of the

1986      _ MAMMALIAN SPECIES OF SPECIAL CONCERN _      19

California Academy of Sciences, captured from Inverness, Marin Co., are, in my opinion, S. v. sonomae.

Rudd (1955b) compared ages, sexes, and weights of S. v. vagrans, S. v. paludivagus, S. ornatus californicus, and S. o. sinuosus. Methods of distinguishing Salt Marsh Wandering Shrews from Ornate Shrews were given in Hennings and Hoffmann (1977) and Junge and Hoffmann (1981). The report by Ford (1986) was completed too late to include details here, but is the most complete account of the distribution and current population status of S. v. halicoetes.

Distribution Records:ALAMEDA CO.: 1 mi N bay Farm Island, Melrose Marsh, 1 (MVZ); Berkeley, 1 (USNM); Dumbarton Point, 1 (KU); Elmhurst, 4 (MVZ); Hayward, 1 (MVZ); Hayward Landing, end of Russell City Road, 6 (MVZ); Melrose, 1 (MVZ); 1 mi NW Newark, 1 (MVZ); Oakland airport, 1 (MVZ); S side Oakland Airport, 12 (MVZ); West Berkeley, 1 (USNM). CONTRA COSTA CO.: Giant (Atlas Powder Co. salt marsh), 1 (MVZ); 3 mi NE Oakley, E side Grizzly Island, 1 (MVZ); mouth San Pablo Creek, 1 (MVZ); San Pablo Creek Salt Marsh, 29 (MVZ); San Pablo Marsh, Richmond (Johnston and Rudd, 1957); salt marsh, 3 mi N Richmond, 1 (CM); salt marsh, 4 mi N Richmond, 1 (CM). SAN FRANCISCO CO.: Lake Merced, 1 (CAS); San Francisco, 4 (CAS), 1 (MVZ), Presidio, San Francisco, 1 (CAS). SAN MATEO CO.: no specific locality, 1 (MVZ); Belmont, 1 (MVZ), 2 (USNM); 0.9 mi NE Coloma, 17 (CAS); 0.5 mi S Chinese Cemetery, Coloma, 1 (CAS); Coloma, 1 (CAS); W approach Dumbarton Bridge, 3 (MVZ); Juncitas, I (SDSNH); Menlo Park, 1 (SDSNH); Pacifica, 0.25 mi E Westview, 1 (CAS); Palo Alto, 2 (LACM); adjacent to Palo alto Yacht Harbor,, I (UDAV); San Mateo, 2 (USNM); Redwood City, 1 (LACM), 3 (MVZ), 23 (SDSNH); Woodside, 1 (SDSNH). SANTA CLARA CO.: 1.75 mi NE Alviso, 79 (MVZ); Los Esteros Road, 0.5 mi NE Alviso (salt_marsh), 20 (MVZ); 1 mi SSW Alviso (salt marsh), 3 (MVZ); county line between Santa Clara and San Mateo counties, on bay between Palo Alto and Redwood City, 2 (CM); Palo Alto, 7 (MVZ), 3 (USNM).

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Arizona Myotis
Myotis lucifugus occultus

1909. Myotis occultus Hollister, Proc. Biol. Soc. Washington, 22:43.
Type Locality: west side Colorado River, 10 mi above Needles, San Bernardino Co., California.
1967. Myotis lucifugus occultus, Findley and Jones, J. Mamm., 48:443.

Distribution: Arizona Myotis occur from southeastern California and Sonora, Mexico, to western Chihuahua, Mexico, and northward in Arizona and western New Mexico (Fenton and Barclay, 1980; Hall, 1981). In California, the Arizona Myotis occurs only along the Colorado River lowlands and in the adjacent desert mountain ranges.

Populations Status: Populations of M. lucifugus have drastically declined in numbers in many parts of its range. Fenton and Barclay (1980) attributed declines, in part, to the use of pesticides, control measures in nursery colonies, collecting of bats by researchers, and disturbance of hibernating individuals. They underscored the importance in disturbances of hibernating bats, noting that it causes bats to lose weight, thus decreasing their chances of survival. Judging from incidental accounts,

20     CALIFORNIA DEPARTMENT OF FISH AND GAME

Arizona Myotis were formerly common along the Colorado River. More recent observations suggest that this population has declined drastically (K. Stager, P. Leitner, pers. comm.). Arizona Myotis, like many other bats, may be sensitive to disturbances in their maternity roosts too. Many females fail to return to maternity colonies in years subsequent to disturbances by humans. They may abandon a colony prematurely, just after the young have learned to fly, but before than have learned to capture insects. This could lower recruitment into the population. Stream channelization and loss of the riparian vegetation may also be factors in the decline of M. l. occultus in California. Pesticide use in agricultural areas along the lower Colorado River and elsewhere could be a contributing factor in the decline (Fenton and Barclay, 1980; Geluso et al., 1976).

Habitat: Both Hollister (1909) and Grinnell (1914) shot Arizona Myotis flying among Cottonwood trees on the floodplain of the Colorado River. Others were collected by Grinnell "over water in a back eddy of the river." Stager (1943) found one Arizona Myotis about 100 ft in from the entrance of a large copper mine in the Riverside Mountains, in the northeastern corner of Riverside County. He also collected individuals from a maternity colony of about 800 bats, located on the underside of a bridge near Blythe. Although M. l. occultus is known only from the low desert along the Colorado River in California, it is most commonly associated with pine forests at elevations from 6000 to 9000 ft in other parts of its range (Barbour and Davis, 1969).

In most areas, roosts of Arizona Myotis have been found beneath bridges and in attics of buildings (Barbour and Davis, 1969). Arizona Myotis probably also use hollows in trees and protected crevices in rocks for roosts. Stager's (1943) record is the only known occurrence in a mine or cave.

Arizona Myotis may migrate out of California to spend the autumn and winter elsewhere, or they may make more local migrations to suitable hibernacula. The earliest and latest records of occurrence in California are 30 April and 16 August, respectively (Stager, 1943).

Recommendations: Highest priority should be given to locating populations, especially maternity colonies, and obtaining estimates of colony size. The most critical need is to establish a data base on population size so that future trends can be more reliably monitored. Where Arizona Myotis may pose a public health problem or a nuisance, exclusion or non_lethal aversion devices should be the only control methods allowed (Barclay et al., 1980; Constantine, 1979).

Remarks: Earlier, I (Williams, 1979) recognized occultus as a species despite evidence presented by Findley and Jones (1967) and Barbour and Davis (1970) indicating interbreeding in an area in New Mexico and southern Colorado between M. lucifugus and occultus. My decision was based on the results of a phenetic analysis of the genus Myotis (Findley, 1972) that suggested that occultus and M. l. carissima (the taxon with which occultus was thought to interbreed) were best place in different species groups. Clearly, genetic studies are needed to resolve these conflicting findings. In the meantime, however, it seems best to follow Findley and Jones (1967) in treating occultus as a subspecies of M. lucifugus.

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1986     _ MAMMALIAN SPECIES OF SPECIAL CONCERN _      21

Distribution Records: IMPERIAL CO.: Potholes, I (SDSNH); 4 mi S Potholes, Colorado River, 1 (MVZ); 5 mi NE Yuma, 1 (KU), 4 (MVZ).
RIVERSIDE CO.: Blythe, 6 (CM), 59 (LACM), 1 (MVZ); Ft. Yuma, 3 (CAS); Ripley, 5 mi S Blythe, 3 (LACM); Riverside Mountains, 1 (LACM).
SAN BERNARDINO CO.: 10 mi N Needles, 2 (USNM).

Arizona Cave Myotis
Myotis velifer velifer

1890. Vespertilio velifer J. A. Allen, Bull. Amer. Mus. Nat. Hist., 3:i77. Type Locality: Santa Cruz del Valle, Guadalajara, Jalisco, Mexico.
1897. Myotis velifer, Miller, N. Amer. Fauna, 13:56.

Distribution: M. velifer velifer is found from extreme southeastern California eastward to western New Mexico and southward to Guatemala. In California, it is known only from the lowlands of the Colorado River and adjacent desert mountain ranges (Vaughan, 1959).

Population Status: Vaughan (1959) found large colonies, each containing approximately 1000 individuals, in several mine tunnels in the Riverside Mountains of Riverside and San Bernardino counties. More recent observations in the area (P. Brown, in litt.), suggest a significant decline in population size. Mines previously occupied now have few bats. The extent of decline and its causes are speculative. Loss of riparian habitat for foraging could be a principal factor, together with human disturbances of colonies. Renewed mining activities and casual exploration of caves and mines by rock collectors and sight_seers may be major sources of disturbances. Use of pesticides might have contributed to the decline by reducing abundance of insects and by poisoning bats.

Habitat: Cave Myotis are habitual cave dwellers and are highly colonial. They inhabit arid zones in the southwestern United States. During the season of reproduction, in spring and summer, they form large colonies in warm caves and mines and less often in buildings and other structures (Barbour and Davis, 1969). In California, they have been found in an old storehouse (Grinnell, 1914) and in mine tunnels (Stager, 1939; Vaughan, 1959). In large portions of their range they are typically associated with Brazilian Free_tailed Bats (Tadarida brasiliensis). Vaughan (1959) noted that Cave Myotis used a variety of temporary roosts: buildings, caves, and mine tunnels.

Vaughan (1959) found that in the vicinity of the Riverside Mountains, Cave Myotis foraged primarily over the floodplain of the Colorado River. He found that they maintained regular foraging paths "over low vegetation, along the files of dense vegetation that line the oxbows and main channel of the river, between the scattered thick patches of vegetation that dot the floodplain, or above bodies of water." He noted that the dense, linear stands of Mesquite, Tamarisk, and Catclaw Acacia bordering still water of oxbow ponds seemed to constitute optimal foraging habitat. Most foraging bats were observed between about 6 and 15 ft above the ground, primarily close to vegetation.

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Kunz (1974) found that most individuals from large colonies in south_central Kansas dispersed nightly for considerable distances to feed. Insects of a variety of orders were consumed; beetles (Coleoptera) comprised the single largest class (Kunz, 1974).

In parts of their geographic range, especially in Kansas, Oklahoma, and Texas, Cave Myotis hibernate in winter (Twente, 1955). M. v. incautus may be quite different in its life history from M. v. velifer, however (Hayward, 1970). Stager (1939) did not find Cave Myotis in California during winter and early spring. He believed that they were only in California from May to October. They probably migrate into Mexico, but this has not been established.

Recommendations: Information pertaining to location and size of extant colonies is needed. Most colonies will probably be located in caves and mines, but buildings may contain some colonies. Data on population size are essential for assessing future trends and making management decisions. Colonies of Cave Myotis located in mines that are to be reactivated will likely abandon the sites as disturbances increase in frequency. Because the bats will most likely leave a roost in autumn, the best time to bat_proof structures is during the winter months, November to March (Constantine, 1979).

Agency biologists working in the southeastern California desert area must be able to identify Myotis velifer. They should be familiar with the situation outlined here, and be aware of the sensitivity of colonies to disturbances. They should be instructed in methods of estimating population size and techniques of non_lethal control of bats in human_made structures (Barclay et al., 1980; Constantine, 1979). Public health, law enforcement, and agricultural officials should refer all reports of bats and all requests for information on eradication of bats to the Department of Health Services, Veterinary Unit in Berkeley.

Remarks: Dr. Patricia Brown (in litt.) has monitored a population of M. velifer in a mine in the Whipple Mountains since 1968. This population declined in size by over 50% between about 1960 and 1980. The decline was at least partly the result of vandals entering the mine and killing several bats. A gradual decrease in numbers has continued since that incident, however.

Hayward (1970) determined that M. v. brevis Vaughan, 1954, was not recognizably distinct from M. v. velifer. Hall (1981) did not cite Hayward's (1970) paper.

Distribution Records:IMPERIAL CO.: 4 mi S Potholes, 1 (MVZ); 5 mi NE Yuma, 5 (MVZ). RIVERSIDE CO. : Alice Mine, Riverside Mountains, 56 (LACM); Dollar Mine, 5.5 mi S, 0.6 mi E Vidal, 1 (CSLB); Mountaineer Mine, 5.5 mi S, 0.6 mi E Vidal, 750 ft, 1 (MVZ); Mule Mountains (P. Brown, in litt.); Riverside Mountains, 35 mi N Blythe, 81 (Vaughan, 1959); Riverside Mountains, NE corner of county, 1 (MVZ); Riverside Mountains, 6 mi S Vidal, 8 (MVZ); Riverside Mountains, 7 mi S Vidal, 10 (MVZ). SAN BERNARDINO CO.: Needles, 3 (MVZ); W side river, above Needles, 2 (USNM); Whipple Mountains (P. Brown, in litt.).

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Riparian Brush Rabbit
Sylvilagus bachmani riparius

1935. Sylvilagus bachmani riparius Orr, Proc. Biol Soc. Washington, 48:29.
Type Locality: 2 mi NE Vernalis, Stanislaus Co., California.

Distribution: Orr (1940) collected specimens from a single locality along the west_side of the San Joaquin River in northern Stanislaus County. He also observed, but did not collect, Riparian Brush Rabbits in adjacent San Joaquin County. Orr (1940) believed that the range of S. b. riparius extended along the San Joaquin River from Stanislaus County to the Delta region. The only presently known population is found on the lower Stanislaus River in Caswell State Park; there are probably other, tiny colonies between Caswell State Park and the confluence of the Stanislaus and San Joaquin rivers (Glenn Basey, in litt.).

Population Status: Only one moderate_sized population is known to be extant within Caswell State Park, San Joaquin County (G. Basey, in litt.). This population, which numbers perhaps less than 100 individuals at the start of the breeding season, was adversely affected by clearing and burning of brush in the Park in winter of 1984_85. Further development of recreation facilities in the Park and continuing brush clearing for fuel control pose significant threats to this population. Elsewhere between Caswell State Park and the San Joaquin River, Basey (in litt.) found only inconclusive evidence of tiny, scattered populations. Use of most of the property in the floodplain of the lower Stanislaus River is restricted by wildlife easements obtained as mitigation for loss of wildlife habitat as a result of construction of New Melones Dam. The Army Corps of Engineers is the administering agency for the easements. In his surveys, Basey (in litt.) found these wildlife areas were being used for rifle ranges, livestock grazing, off_road vehicle recreation, and other activities. Although Basey's studies are still in progress, activities such as these probably compound the threats to remaining populations of Riparian Brush Rabbits.

The Army Corps of Engineers is preparing to clear much of the brush and trees from within the lower San Joaquin River floodplain, between an area below Friant Dam, Fresno Co., and the delta in San Joaquin Co. (U.S. Fish and Wildlife Service, in litt.). Although no extant populations of Riparian Brush Rabbits have been found yet along the San Joaquin River, these activities pose a substantial threat to any remaining populations there and will virtually preclude reestablishment of populations in the future. The major threat to remaining populations may stem from annual flooding. All land bordering the diked floodplains of the lower San Joaquin and Stanislaus rivers is cultivated or otherwise developed. In most areas, much or all of the woody vegetation has been removed for control of stream flow and to enhance growth of herbaceous plants for livestock grazing. In times of severe flooding, such as in the winters of 1979_80, 1982_83, and 1985_86, nearly all habitat available to Riparian Brush Rabbits is inundated. Animals living in the floodplain are forced to shelter on dikes or in areas lacking adequate cover, exposing them to increased predation and cold, wet weather. A single, severe episode of flooding, only slightly worse than was witnessed during March, 1986, could possibly cause the extinction of remaining populations.

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The Riparian Brush Rabbit is currently designated a Resident Small Game species and may be hunted. Although the effect of hunting on populations of Brush Rabbits, in general, are probably Insignificant, hunting might easily extirpate most of the small, scattered populations of Riparian Brush Rabbits outside of Caswell State Park.

Habitat: In general, brush rabbits are associated with chaparral or other types of dense brush (Chapman, 1974). Riparian Brush Rabbits occupy dense thickets of Wild Rose (Rosa sp.), Willows (Salix spp.), and Blackberries (Rubus sp.) growing along the banks of the river. Orr (1940) never observed Riparian Brush Rabbits in loose brush or in open fields. Studies by Glenn Basey (in litt.) indicated that, in summer when herbaceous plants were largest and provided densest cover, Riparian Brush Rabbits used weedy fields and clearings adjacent to patches of shrubs. These areas of herbaceous vegetation were not entered in autumn and winter when the plants were dead and cover was minimal or absent. Basey (in litt.) found that patches of herbaceous growth at the immediate edge (within less than a meter) of shrubs were important sources of food.

Distribution Records:SAN JOAQUIN CO.: Caswell State Park, 2 (CSCS); San Joaquin River, extreme southern part of county (Orr, 1935). STANISLAUS CO.: Kincaid's Ranch, 2 mi NE Vernalis, W side San Joaquin River, 2 (CAS), 3 (MVZ).

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Point Arena Mountain Beaver Aplodontia rufa nigra

1914. Aplodontia nigra Taylor, Univ. California Publ. Zool., 12:297.
Type Locality: Point Arena, Mendocino Co., California.
1918. Aplodontia rufa nigra, Taylor, Univ. California Publ. Zool., 17:479.

Distribution: Aplodontia rufa nigra is known only from the vicinity of Point Arena, Mendocino County. According to Taylor (1918), it originally occupied a total area of about 24 square miles. Camp (1918) stated that known colonies extended from the town of Point Arena to Alder Creek, 7.5 miles north of town.

Population Status: An investigation of the status of the Point Arena Mountain Beaver by Dale Steele is presently in progress (U.S. Fish and Wildlife Serv., in litt.). Some populations are threatened by housing developments and others are small and apparently vulnerable to any event that would alter the character of their habitat. The restricted distribution of this population and the fact that Mountain Beavers are often heavily persecuted by humans gives additional cause for concern. Logging may benefit Mountain Beavers in that logging opens up the forest and stimulates growth of deciduous trees and herbaceous plants. Urbanization generally results in the decline or local extirpation of Mountain Beavers. Home developments are likely in the range of the Point Arena Mountain Beaver.

Habitat: Specific information on the Point Arena Mountain Beaver was given by Camp (1918). Only north_facing slopes of ridges and gullies were found to be inhabited. In general, Mountain Beavers inhabit wooded regions along the Pacific Coast with abundant moisture and herbaceous plants for food. Soils must be sufficiently soft for