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Overview
Brief Summary
Description
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Mammal Species of the World
Click here for The American Society of Mammalogists species account
- Original description: Merriam, C.H., 1893. Descriptions of eight new ground squirrels of the genera Spermophilus and Tamias from California, Texas, and Mexico, p. 129. Proceedings of the Biological Society of Washington, 8:129-138.
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Distribution
Range Description
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National Distribution
United States
Origin: Native
Regularity: Regularly occurring
Currently: Present
Confidence: Confident
Type of Residency: Year-round
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Global Range: (1000-5000 square km (about 400-2000 square miles)) The range is restricted to the central and western San Joaquin Valley and neighboring areas to the west in the inner Coast Ranges of California (e.g., Cuyama Valley, Panoche Valley, Carrizo Plain, Elkhorn Plain) (Best et al. 1990). Elevational range extends from about 50 meters on the floor of the San Joaquin Valley to around 1,100 meters in the Temblor Range, but antelope squirrels are not common above about 800 meters on the ridges and plains west of the San Joaquin Valley proper (Williams 1980; D.F. Williams, unpubl. data). Populations now exist primarily in marginal habitats of low foothills and mountains on the western edge of the San Joaquin Valley; significant populations occur only in western Kern County at Elk Hills and on portions of the Carrizo and Elkhorn plains. In the northern part of range, low density populations occur in the Panoche and Kettleman hills (California Department of Fish and Game 1990, Harris and Stearns 1991).
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Physical Description
Size
Size in North America
Length:
Average: 249 mm males; 238 mm females
Range: 234-267 mm males; 230-256 mm females
Weight:
Average: 155 g
Range: 142-179 g
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Diagnostic Description
Smaller than the California ground squirrel (Spermophilus beecheyi), which is an abundant species throughout the San Joaquin Valley. The latter lacks the distinctive white stripe on its sides. Antelope ground squirrels are often mistaken for chipmunks (Neotamias spp.), but the squirrels lack the black and white stripes on their faces and backs.
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Type Information
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Mammals
Sex/Stage: Male; Adult
Preparation: Skin; Skull
Collector(s): C. Streator
Year Collected: 1893
Locality: Tipton, San Joaquin Valley, Tulare County, California, United States, North America
- Type: Merriam, C. H. 1893 Dec 28. Proceedings of the Biological Society of Washington. 8: 129.
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Ecology
Habitat
Habitat and Ecology
Habitats in order of decreasing favourability: (1) xerophytic stage of alkali desert scrub with shrubs sparsely distributed and with friable soils, at elevations greater than 4,000 feet, (2) annual grassland with less than six inches annual precipitation, friable soils, and abundance of Dipodomys ingens, (3) halophytic stage of alkali desert scrub with shrubs sparsely distributed and with friable soils, at elevations above 2,200 feet, and (4) annual grassland with 7-9 inches annual precipitation and abundance of Dipodomys heermanni. Habitats that are avoided included valley floor areas of alkaline soils, iodine bush, and spring saltbush, probably due to high water tables (Biosystems Analysis 1989). See also Best et al. (1990) for habitat synopsis. These squirrels seldom dig their own burrows; most often they use burrows made by other small mammals. Preferred burrow locations are under shrubs, in the banks of arroyos at the base of alluvial fans, and along roadcuts, pipelines, and drilling platforms (Biosystems Analysis 1989).
Breeding season coincides with availability of green vegetation. Young are born in March, first seen above ground about the first week of April, at which time they gather food. Gestation lasts 26 days. One breeding season per year. Litter size is 6-12 (average nine). May live five plus years, though usual life span is less than one year.
Half of the remaining habitat supports fewer than one animal per hectare, 15% of the remaining habitat supports 3-10 animals per hectare (generally four or fewer per hectare, California Department of Fish and Game 1990).
It is omnivorous, and the diet is mainly green vegetation, grass and forb seeds, and insects. It feeds on insects during the dry season, from mid-April to December. Green vegetation is important December-April. Generally stays underground when air temperature is less than 10C (California Department of Fish and Game 1990). Little activity in hot weather, when most active in morning and late afternoon. No evidence of hibernation or aestivation, yet reported to become fat in late spring and disappear during hot months (Best et al. 1990).
Systems
- Terrestrial
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Comments: Habitat consists of dry flat or rolling terrain, with slopes less than 10-14 degrees, on alluvial and loamy soils, soils with sandy or gravelly texture, or fine-grained soils that are nearly brick-hard when dry. The species inhabits grassy, sparsely shrubby ground (shrubs include saltbush, ephedra, bladder pod, goldenbush, snakeweed, etc.); it also occurs in areas lacking shrubs where giant kangaroo rats are present. Habitats in order of decreasing favorability: (1) xerophytic stage of alkali desert scrub with shrubs sparsely distributed and with friable soils, at elevations greater than 4,000 feet, (2) annual grassland with less than 6 inches annual precipitation, friable soils, and abundance of Dipodomys ingens, (3) halophytic stage of alkali desert scrub with shrubs sparsely distributed and with friable soils, at elevations above 2,200 feet, and (4) annual grassland with 7-9 inches annual precipitation and abundance of Dipodomys heermanni. Habitats that are avoided included valley floor areas of alkaline soils, iodine bush, and spring saltbush, probably due to high water tables (Biosystems Analysis 1989). See also Best et al. (1990) for habitat synopsis. These squirrels seldom dig their own burrows; most often they use burrows made by other small mammals. Preferred burrow locations are under shrubs, in the banks of arroyos at the base of alluvial fans, and along roadcuts, pipelines, and drilling platforms (Biosystems Analysis 1989).
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Migration
Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Home range on Elkhorn Plain 5-20 ha (average 14 ha) (California Department of Fish and Game 1990); another study reported home range of about 4.4 ha (Hawbecker 1958). Hawbecker (1958) recorded moves of up to 1.3 km by an immature male and up to 0.9 km by an adult female.
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Trophic Strategy
Comments: Omnivorous; diet mainly green vegetation, grass and forb seeds, and insects. Filaree (Erodium cicutarium) and red brome (Bromus rubens) reported to be important food items (Hawbecker 1947). Feeds on insects during the dry season, from mid-April to December. Green vegetation is important December-April.
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Population Biology
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 21 - 80
Comments: This species is represented by several dozen distinct occurrences or subpopulations. It occurs at scattered sites in low density throughout much of the historical range. Moderate efforts have been made at locating populations.
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Global Abundance
100,000 - 1,000,000 individuals
Comments: Total population size is unknown. Based on 3-10 squirrels per hectare on 41,300 hectares of the best remaining habitat (Williams 1980), population size would be at least 124,000-413,000. The species is common within the Carrizo Plain National Monument.
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General Ecology
Half of remaining habitat supports fewer than 1 animal/ha, 15% of the remaining habitat supports 3-10 animals/ha (generally 4 or fewer per ha, California Department of Fish and Game 1990). Spermophilus beecheyi reportedly may restrict range of A. NELSONI (see Best et al. 1990). Among several predators, badger is most important. Lives in small groups.
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Life History and Behavior
Cyclicity
Comments: Generally stays underground when air temperature is less than 10 C (California Department of Fish and Game 1990). Little activity in hot weather, when most active in morning and late afternoon. No evidence of hibernation or estivation, yet reported to become fat in late spring and disappear during hot months (Best et al. 1990).
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Life Expectancy
Lifespan, longevity, and ageing
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Reproduction
Breeding season coincides with availability of green vegetation. Young are born in March, first seen above ground about the first week of April, at which time they gather food. Gestation lasts 26 days. One breeding season per year. Litter size is 6-12 (average 9). May live 5+ years, though usual life span is less than 1 year.
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Conservation
Conservation Status
IUCN Red List Assessment
Red List Category
Red List Criteria
Version
Year Assessed
Assessor/s
Reviewer/s
Justification
History
- 2000Endangered
- 1996Endangered
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National NatureServe Conservation Status
United States
Rounded National Status Rank: N2 - Imperiled
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NatureServe Conservation Status
Rounded Global Status Rank: G2 - Imperiled
Reasons: Occurs in the San Joaquin Valley and neighboring valleys, California; locally common in some protected areas; sparsely distributed at widely scattered sites elsewhere where habitat protection and population viability are uncertain.
Intrinsic Vulnerability: Not intrinsically vulnerable
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Status
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Trends
Population
This species is represented by several dozen distinct occurrences or subpopulations. It occurs at scattered sites in low density throughout much of the historical range. Moderate efforts have been made at locating populations.
The current trend is not well known but, since 1979, populations have disappeared from many of the smaller habitat clusters on the floor of the San Joaquin Valley (Williams 1980, USFWS 1998). However, recent protection efforts in the southwestern San Joaquin Valley likely have slowed the rate of decline, and the species remains common in some protected areas. Probably the rate of decline is less than 30% over the past 10 years.
Prior to cultivation, the area within which this species was distributed was approximately 3.5 million acres (about 14,000 square kilometres = historical extent of occurrence). The species is presently extant in less than 20% of its former range. In 1979, extant, uncultivated habitat (but including land occupied by towns, roads, canals, pipelines, strip mines, airports, oil wells, and other developments) for the species was estimated at 275,200 hectares (680,000 acres, 2,752 sqkm) (Williams 1980). None of the best historical habitat remained.
One study indicated that densities in open Ephedra plots and shrubless plots ranged from 0.8 to 8.0 squirrels per hectare, but all but two sites had densities of four or less per hectare. Densities on shrubless, grassy dominated sites were equal to or higher than those on shrubby sites (Harris and Stearns, 1991).
Population Trend
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Global Short Term Trend: Relatively stable to decline of 30%
Comments: The current trend is not well known but, since 1979, populations have disappeared from many of the smaller habitat clusters on the floor of the San Joaquin Valley (Williams 1980, USFWS 1998). However, recent protection efforts in the southwestern San Joaquin Valley likely have slowed the rate of decline, and the species remains common in some protected areas. Probably the rate of decline is less than 30% over the past 10 years.
Global Long Term Trend: Decline of 30-70%
Comments: Prior to cultivation, the area within which this species was distributed was approximately 3.5 million acres (about 14,000 square kilometers = historical extent of occurrence). The species is presently extant in less than 20% of its former range. In 1979, extant, uncultivated habitat (but including land occupied by towns, roads, canals, pipelines, strip mines, airports, oil wells, and other developments) for the species was estimated at 275,200 hectares (680,000 acres, 2,752 sq km) (Williams 1980). None of the best historical habitat remained. Only about 41,300 hectares (102,000 acres, 413 sq km) was rated as fair to good quality, supporting from 3 to 10 antelope squirrels per hectare (1 to 4 per acre, 300-1,000 per sq km) (Williams 1980, USFWS 1998).
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Threats
Threats
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Degree of Threat: B : Moderately threatened throughout its range, communities provide natural resources that when exploited alter the composition and structure of the community over the long-term, but are apparently recoverable
Comments: The decline is a result of loss of habitat due to agricultural and urban development as well as oil and gas exploration practices. Primary exisiting threats include loss of habitat due to agricultural development, urbanization, and petroleum extraction, and the use of rodenticides for ground squirrel control. Overgrazing and associated loss of shrub cover is a concern in some areas. These threats will be alleviated by implementation of the San Joaquin Endangered Species Recovery Plan.
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Management
Conservation Actions
Significant populations occur on the Carrizo Plain National Monument (encompasses most of the Carrizo Plain and Elkhorn Plain). The national monument designation applies only to public lands managed by the Bureau of Land Management. Existing private lands within the monument boundaries are not affected by the designation. The overall Carrizo Plain, which includes some state owned land, will continue to be jointly managed by the Bureau of Land Management, the California Department of Fish and Game, and The Nature Conservancy.
Small populations are also found within two preserves in Kern County owned by The Nature Conservancy, and two reserves owned by the California Department of Fish and Game (in Kern County and Tulare County). See California Department of Fish and Game (1990) for brief comments on protected areas inhabited by this species (e.g., Elkhorn Plain Ecological Preserve, Carrizo Plain, and others).
The California Department of Fish and Game is involved in several conservation efforts, including the Metropolitan Bakersfield Habitat Conservation Plan (HCP), the California Department of Corrections Electric Fence HCP, the Coles Levee area 2081 Agreement, and the Arco Western Energy HCP.
Acquisition and protection of lands with extant populations of antelope squirrels in the Panoche and Kettleman Hills and on the San Joaquin Valley floor should be the highest priority for this species (Harris and Stearns 1991). Also need to determine the population density for the range of habitats occupied; additional inventories are needed, mostly on private land, and also to monitor populations, and obtain data on demography, dispersal, and reproduction.
USFWS (1998) stated that the actions required to conserve the San Joaquin antelope squirrel, in approximate order of importance, are: 1. Determine habitat management prescriptions on the southern San Joaquin Valley floor. 2. Inventory potential habitat in the Allensworth, Semitropic Ridge, and Kettleman Hills natural areas, and along the western edge of the Valley between Pleasant Valley, Fresno County, and McKittrick Valley-Lokern Area, Kern County. 3. Protect additional habitat in the Pixley National Wildlife Refuge-Allensworth Natural Area. 4. Develop and implement a population monitoring program at sites representative of their existing geographic range. 5. Protect additional habitat in the Panoche Region of western Fresno and eastern San Benito Counties. 6. Protect additional habitat in western Kern County. 7. Protect additional habitat in the Semitropic Ridge Natural Area. 8. Reevaluate the status of San Joaquin antelope squirrels within three years of recovery plan approval.
Management Requirements: Protect habitat from overgrazing and loss of shrub cover; maintain sparse shrub cover and associated species; avoid unnecessary rodenticide use. Care should be taken not to destroy burrows near man-made structures in previously disturbed sites (Biosystems Analysis 1989).
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Management Requirements: Protect habitat from overgrazing and loss of shrub cover; maintain sparse shrub cover and associated species; avoid unnecessary rodenticide use. Care should be taken not to destroy burrows near man-made structures in previously disturbed sites (Biosystems Analysis 1989).
Biological Research Needs: Obtain data on demography, dispersal, and reproduction.
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Global Protection: Several (4-12) occurrences appropriately protected and managed
Comments: Significant populations occur on the Carrizo Plain National Monument (encompasses most of the Carrizo Plain and Elkhorn Plain). The national monument designation applies only to public lands managed by the Bureau of Land Management. Existing private lands within the monument boundaries are not affected by the designation. The overall Carrizo Plain, which includes some state owned land, will continue to be jointly managed by the Bureau of Land Management, the California Department of Fish and Game, and The Nature Conservancy.
Small populations are also found within two preserves in Kern County owned by The Nature Conservancy, and two reserves owned by the California Department of Fish and Game (in Kern County and Tulare County). See California Department of Fish and Game (1990) for brief comments on protected areas inhabited by this species (e.g., Elkhorn Plain Ecological Preserve, Carrizo Plain, and others).
The California Department of Fish and Game is involved in several conservation efforts, including the Metropolitan Bakersfield Habitat Conservation Plan (HCP), the California Department of Corrections Electric Fence HCP, the Coles Levee area 2081 Agreement, and the Arco Western Energy HCP.
Needs: Acquisition and protection of lands with extant populations of antelope squirrels in the Panoche and Kettleman Hills and on the San Joaquin Valley floor should be the highest priority for this species (Harris and Stearns 1991).
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Relevance to Humans and Ecosystems
Risks
Stewardship Overview: USFWS (1998) stated that the actions required to conserve the San Joaquin antelope squirrel, in approximate order of importance, are: 1. Determine habitat management prescriptions on the southern San Joaquin Valley floor. 2. Inventory potential habitat in the Allensworth, Semitropic Ridge, and Kettleman Hills natural areas, and along the western edge of the Valley between Pleasant Valley, Fresno County,and McKittrick Valley-Lokern Area, Kern County. 3. Protect additional habitat in the Pixley National Wildlife Refuge- Allensworth Natural Area. 4. Develop and implement apopulation monitoring program at sites representative of their existing geographic range. 5. Protect additional habitat in the Panoche Region of western Fresno and eastern San Benito Counties. 6. Protect additional habitat in western Kern County. 7. Protect additional habitat in the Semitropic Ridge Natural Area. 8. Reevaluate the status of San Joaquin antelope squirrels within 3 years of recovery plan approval.
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Wikipedia
San Joaquin antelope squirrel
The San Joaquin antelope squirrel or Nelson's antelope squirrel.Ammospermophilus nelsoni, is a species of antelope squirrel, in the San Joaquin Valley of the U.S. state of California.
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Distribution and habitat
The San Joaquin antelope squirrel is found in the San Joaquin Valley, including slopes and ridge tops along the western edge of the valley.[2] It is endemic to the region, and is found in a much smaller range today than it originally inhabited. Since the San Joaquin Valley fell under heavy agricultural cultivation, habitat loss combined with rodenticide use has reduced the squirrel's numbers enough that it is now listed as a threatened species.
Most of today's remaining San Joaquin antelope squirrels can be found in the Carrizo Plain, where their original habitat remains undisturbed. The squirrels live in small underground familial colonies on sandy, easily excavated grasslands in isolated locations in San Luis Obispo and Kern Counties. Common vegetation associated with the squirrel includes Atriplex and Ephedra, and some junipers.[3] The binomial of this species commemorates the American naturalist Edward William Nelson.
Description
Physical Characteristics
The San Joaquin antelope squirrel is dull yellowish-brown or buffy-clay in color on upper body and outer surfaces of the legs with a white belly and a white streak down each side of its body in the fashion of other antelope squirrels.[2] The underside of the tail is a buffy white with black edges.[2] Males are approximately 9.8 inches and females are approximately 9.4 inches in length.[2]
Breeding
Studies by Hawbecker provide abundant information on breeding and the life cycle of Nelson's antelope squirrel.[3][4][5] They breed in late winter to early spring and have nearly all their young in March.[5] Once pregnant, gestation lasts a little less than a month.[3] The young do not emerge from their dens until approximately the first week of April.[4] Nelson's antelope squirrel has only one breeding season, which is timed appropriately so that the young are born during the time of year when green vegetation is the most abundant.[4]
Growth
Weaning is thought to start or be completed even before the young emerge.[3] Once above ground, young are seen foraging for food independently.[3] During the weaning period, the mother feeds alone and ignores any attempt of the young trying to nuzzle or nurse from her.[3] A female mother will sometimes spend the night in a different den if necessary.[3] By early to mid-May the young squirrels have had their juvenile pelage for some time and begin to show the changes into adult pelage.[3] By summer, the adult pelage is present.[3] Once an individual has reached adulthood it is difficult to tell differences in age.[4] Nelson's antelope squirrel is a short-lived species that often does not survive to a year.[4] However, there have been several individuals that have lived more than four years in the wild.[4]
It is omnivorous, feeding mostly on green plants during the winter and insects and carrion when these are available. It occasionally caches food. The squirrels live in small underground familial colonies on sandy, easily excavated grasslands in isolated locations in San Luis Obispo and Kern Counties.
Group size and home range
Colonies have about six or eight individuals, however these individuals are not distributed evenly across their range.[6] There is usually about 1 per hectare.[7] Nelson's antelope squirrel prefers deep, rich soil types since they are easy to dig through in both winter and summer temperatures.[5][8] Although these squirrels may dig for food, they do not make their own burrows. Instead they claim abandoned Dipodomys (kangaroo rats) burrows as their own.[5] Both males and females have the same size home range of about 4.4 hectare.[4] Of course, there are areas of concentration within this range where the squirrels spend the majority of their time.
Diet
It is omnivorous, feeding on seeds, green vegetation, insects, and dried animal matter.[7] It occasionally caches food. Redstem fialree (Erodium cicutarium) and brome grass (Bromus rubens) are important food items for the squirrels.[5] However, their diet may differ depending on the time of day or time of year. Green vegetation is the most common diet type from December to mid-April because it is the most abundant during this period.[3] Likewise, incests make up more than 90% of the squirrel's diet from mid-April to December because they are more abundant.[3] Although seeds are available for most of the year, it is not the preferable diet of the squirrels.[3] They will choose insects or green vegetation when available over seeds, even if the seeds are more abundant and easier to access.[3] Some speculate that this could be due to the higher amount of water in insects and green vegetation, which would be necessary for the species to survive in such a hot, dry climate.[3] Unfortunately for the Nelson's antelope squirrel, there is not an abundant water source nearby.[8] Under laboratory conditions, the squirrels readily accept water.[8] However, they can also survive at least 7 months in the shade without water.[8] At the end of 7 months they appeared relatively healthy and not at all emaciated.[8]
Behavior
Nelson's antelope squirrels are social animals.[7] When individually taken out of their home range and released in an unknown area, they seem helpless and confused.[8] They do not expend much energy throughout the day because of the extreme temperatures in their environment.[5] In fact, when in the direct sunlight, a temperature of 31-32°C can kill them.[4] Therefore, there is little activity from the squirrels during the heat of the day. Although there is no evidence of hibernation, the squirrels are not bothered by the cold and can survive temperatures below freezing, in their burrows.[4] They are not early risers and are usually not seen until after sunrise, however it does forage in the morning and evening, avoiding the midday heat.[7][8] Around noon the squirrels disappear into their burrows and are not seen again until about 2 pm at the earliest.[7] On moderate days, the squirrels will take their time foraging, in contrast to bringing as much food back to their burrows as quickly as possible on hot or cold days.[5] The squirrels are also known to fully stretch out and roll over in the dust on the ground. These dust baths appear to be very enjoyable activities for the squirrels and may also be used to prevent infestation of parasites.[9]
Nelson's antelope squirrels are cautious when emerging from their burrows.[7] They have a specific route that they follow when foraging for food. If danger seems near, they will run into a burrow along their foraging route to get to safety.[5] They move quickly and do not spend much time in one place.[3] They are particular about what they choose to eat and very rarely even waste time to pick up food they are not interested in.[2] There are other features in addition to their quick movements that help keep them from danger. They whitish color of the underside of their tail can be seen when they run. The squirrels will curl their tail forward over their back and flick and twitch it back and forth as it runs.[7] This movement can present the illusion of thistledown fluttering in the wind, which could be ignored by any potential predators.[7]
To further help prevent predation, the Nelson's antelope squirrel has an alarm call. These alarm calls are not loud, but associated with convulsive body movements.[6] Horned larks and the white-crowned sparrow also aid in predator detection.[5] Squirrels will listen to alarm calls given by these two birds. The badger (Taxidea taxus) is a main predator of Nelson's antelope squirrel and will destroy burrows to get its meal.[2] Coyotes (Canis latrans) and San Joaquin Valley Kit Fox (Vulpes macrotis mutica) are also known to consume the squirrels, but they are not a main part of their diet.[5][10]
Threats
Increasing agriculture and urban development is an increasing problem for Nelson's antelope squirrel.[2][11][12] This species will not colonize cultivated land. Therefore, an increase in agriculture land is taking away their habitat and laving them with no alternative. Grazing livestock further destroys what habitat may be left, and exotic plants are able to take over native grasses that the squirrel forages upon and relies on for shade and cover.[12] Also, pesticide drift from nearby agricultural fields encroaches in on the existing squirrel habitat.[11] Not only are these practices affecting the population of the Nelson's antelope squirrel, but they are also causing problems for other native animal and plant species in the San Joaquin Valley. Native plant species such as the kern mallow, San Joaquin woolly threads, California jewelflower, and Bakersfield cactus are all federally endangered plant species that are being outcompeted by invasive plant species.[12] Many invasive plants grow in very dense patches. These dense patches are not adequate habitats for Nelson's antelope squirrel and many other San Joaquin Valley Species.
Conservation Efforts
There have been attempts to manage the invasive species and other anthropogenic causes to species decline in the San Joaquin Valley.[2][11][12][13] Prescribed burns are one option to control invasive plant species, however this method can cause native species to also be killed and can be expensive.[12] Studies determining the effects of cattle grazing on the land are also being done so that plans can be developed to reduce the impact on the land. Suggestions of using prescribed grazing to help reduce the growth of non-native species in the valley.[12]
Other control efforts include chemical and mechanical treatments, however these too can be time consuming and expensive, especially for large areas.[12] Also, the use of herbicides could potentially negatively affect species in the San Joaquin Valley if there are significant winds that spread the chemicals.[12] The U.S. Fish and Wildlife Service (USFWS) has a recovery plan dated 1998 that includes the ideas of using Safe Harbor Agreements (SHA's) under Section 10 of the Endangered Species Act.[13] This could potentially begin a relationship between the USFWS and the farm landowners to help determine the best compromise in order to manage the endangered species of the valley.
A multispecies approach to conservation is important because of the increasing number of native species becoming threatened and endangered in the San Joaquin Valley. Management on an ecosystem level would allow the role of all the species to be taken into account. Also, an increase in awareness and education of the public around the Valley may further help increase funding for conservation and management plans. Monitoring and studying of the species is needed to determine just how threatened the species is and what needs to be done to reestablish stable populations in the valley.[2][12]
Unfortunately, most information found on the Nelson's antelope squirrel discuss the problems and reasons of declines, but do not give much insight on the potential recovery of the species. Even in 1918, Grinnell and Dixon believed it to only be a matter of time before the species faces extinction.[7]
References
- ^ Whitaker Jr., J. O. & NatureServe (Hammerson, G. & Williams, D. F. (2008). Ammospermophilus nelsoni. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 6 January 2009.
- ^ a b c d e f g h i Best, T.L., A.S. Titus, C.L. Lewis, and K. Caesar. (1990). "Ammospermophilus nelsoni". The American Society of Mammalogists 367: 1–7.
- ^ a b c d e f g h i j k l m n o Hawbecker A.C. (1975). The biology of some desert-dwelling ground squirrels, in Rodents in desert environments. The Hague, Netherlands. pp. 277–303.
- ^ a b c d e f g h i Hawbecker A.C. (1958). "Survival and home range in the Nelson antelope ground squirrel.". Journal of Mammalogy 34: 207–215.
- ^ a b c d e f g h i j Hawbecker A.C. (1953). "Environment of the Nelson antelope ground squirrel.". Journal of Mammalogy 32: 324–334.
- ^ a b Taylor, W.P. (1916). "A new spermophile from the San Joaquin Valley, California, with notes on Ammospermophilus nelsoni nelsoni Merriam". University of California Publications in Zoology. 17: 15–20.
- ^ a b c d e f g h i Grinnell, J., and J. Dixon. (1916). "Natural History of the ground squirrels of California.". Monthly Bulletin of the State Commission of Horticulture (California) 7: 597–708.
- ^ a b c d e f g Hawbecker A.C. (1947). "Moisture Requirements of the Nelson Antelope Ground Squirrel.". Journal of Mammalogy 28 (2): 115–125. doi:10.2307/1375452. JSTOR 1375452.
- ^ Hawbecker A.C. (1959). "Parasites of Ammospermophilus nelsoni.". Journal of Mammalogy 40 (3): 446–447. doi:10.2307/1376582. JSTOR 1376582.
- ^ Hawbecker A.C. (1943). "Food of the San Joaquin Kit Fox.". Journal of Mammalogy 24: 449.
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Source:
Wikipedia
Unreviewed
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