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Overview

Brief Summary

Description

Although large (for a kangaroo rat) and assertive, the Giant Kangaroo Rat occupies a relatively small home range (averaging 0.04 hectares). It keeps quite busy and is remarkably manipulative of this territory, however, storing seeds both above and belowground, clearing the ground of all plant remains after it has harvested seeds, and frequently reshaping its burrows. It destroys shrubs that sprout within its territory, and so has a significant impact on the plant communities where it lives out a solitary life.

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  • Original description: Merriam, C.H., 1904.  New and little known kangaroo rats of the genus Perodipus, p. 141.  Proceedings of the biological society of Washington, 17:139-145.
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Biology

These nocturnal animals hide in their burrows during the heat of the day, plugging the burrow entrance with loose soil and only emerging at night (2) (6). They are solitary and territorial, advertising their territory with a loud drumming produced by the thumping of the hind feet (2). Burrows tend to be fairly shallow and contain many connected enlarged chambers; one that acts as a nest and the rest used to store food (7). Kangaroo rats feed on seeds, vegetation and insects, storing a cache of seeds to see them through periods of drought (1). In years of good rainfall, a female may give birth to up to three litters and individuals born that year may themselves begin breeding when only 12 to 13 weeks old (2).
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Description

The giant kangaroo rat is the largest of more than 20 species of kangaroo rats, which are small rodents that (as their name would suggest) move by hopping on their back legs. The front limbs are reduced and used only for digging, whist the hind limbs are long and powerful and the exceptionally long tail is used for balance (4). The hind legs can propel an individual in leaps of over 2 metres when escaping from predators (2). As with other kangaroo rats, this species has large eyes, small rounded ears and a somewhat rounded body (5). The fur is buff-coloured, and it has a white belly and a white stripe across the hindquarters. The tufted tail is dark but has white lines along either side (5).
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Distribution

The giant kangaroo rat has an extremely small range limited to the west-central region of the U.S. state of California. Specifically, it is currently found only as far north and west as Fresno County and as far east and south as San Luis Obispo and Bakersfield Counties

Biogeographic Regions: nearctic (Native )

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Range Description

The species' range is endemic to California in the United States and is confined to a narrow strip along the southwestern border of the San Joaquin Valley and a few nearby valleys to the west, including the Carrizo and Elkhorn plains and upper Cuyama Valley, with scattered colonies in the Ciervo, Kettleman, Panoche, and Turney Hills, and the Panoche Valley (Grinnell, 1922; Hall, 1981; Williams and Kilburn, 1991; Williams et al., 1993). Its historical range extended from Merced County south to the base of the Tehachapi Mountain in Kern County, and west to eastern San Luis Obispo County and extreme northern Santa Barbara County (Williams et al. 1993). Its elevational range extends to about 868 m asl (400-2,850 feet).

The population is currently fragmented into six major geographic units: 1) the Panoche region in western Fresno and eastern San Benito counties; 2) Kettleman Hills in Kings County; 3) San Juan Creek Valley in San Luis Obispo County; 4) western Kern County in the area of the Lokern, Elk Hills, and other uplands around McKittrick, Taft, and Maricopa; 5) Carrizo Plain in eastern San Luis Obispo County; and 6) Cuyama Valley in Santa Barbara and San Luis Obispo counties (see USFWS, 1998). These major units are fragmented into more than 100 smaller populations, many of which are isolated by several miles of barriers such as steep terrain with plant communities unsuitable as habitat, or agricultural, industrial, or urban land without habitat for this species (USFWS,1998).
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endemic to a single state or province

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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: (5000-20,000 square km (about 2000-8000 square miles)) The range is confined to a narrow strip along the southwestern border of the San Joaquin Valley and a few nearby valleys to the west, including the Carrizo and Elkhorn plains and upper Cuyama Valley, with scattered colonies in the Ciervo, Kettleman, Panoche, and Turney Hills, and the Panoche Valley (Grinnell 1922, Hall 1981, Williams and Kilburn 1991, Williams et al. 1993). Historical range extended from Merced County south to the base of the Tehachapi Mountains in Kern County, and west to eastern San Luis Obispo County and extreme northern Santa Barbara County (Williams et al. 1993). Elevational range extends to about 868 meters (400-2,850 feet).

The population is currently fragmented into six major geographic units: 1) the Panoche region in western Fresno and eastern San Benito counties; 2) Kettleman Hills in Kings County; 3) San Juan Creek Valley in San Luis Obispo County; 4) western Kern County in the area of the Lokern, Elk Hills, and other uplands around McKittrick, Taft, and Maricopa; 5) Carrizo Plain in eastern San Luis Obispo County; and 6) Cuyama Valley in Santa Barbara and San Luis Obispo counties (see USFWS 1998). These major units are fragmented into more than 100 smaller populations, many of which are isolated by several miles of barriers such as steep terrain with plant communities unsuitable as habitat, or agricultural, industrial, or urban land without habitat for this species (USFWS 1998).

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Historic Range:
U.S.A. (CA)

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Range

Endemic to the San Joaquin Valley in California, USA (1).
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Physical Description

Morphology

The giant kangaroo rat is the largest of all kangaroo rats and has a body length ranging from 15 to 20 cm and a tail length of 18 to 21.5 cm. Unlike many other kangaroo rats, D. ingens possesses five toes on each hind foot, a white stripe running across its hindquarters, and a white belly. It also has a distinctive tail that is dark colored on the top and bottom with white lines on both sides.

Other Physical Features: endothermic ; bilateral symmetry

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Size

Length: 35 cm

Weight: 180 grams

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Size in North America

Sexual Dimorphism: Males are larger than females.

Length:
Average: 333.2 mm males; 328.9 mm females

Weight:
Average: 138 g males; 132 g females
Range: 93-180 g males; 101-195 g females
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Diagnostic Description

Other kangaroo rats in California have only four toes on the hind foot or usually have a head and body length of less than 130 mm (Jameson and Peeters 2004).

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Type Information

Type for Dipodomys ingens
Catalog Number: USNM 128805
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Mammals
Sex/Stage: Male; Adult
Preparation: Skin; Skull
Collector(s): L. Goldman
Year Collected: 1903
Locality: Painted Rock, 20 [= 12 (see Grinnell 1922)] mi SE of Simmler, Carrizo Plain, San Luis Obispo County, California, United States, North America
  • Type: Merriam, C. H. 1904 Jul 14. Proceedings of the Biological Society of Washington. 17: 141.
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Ecology

Habitat

California Central Valley Grasslands Habitat

This taxon is found in the California Central Valley grasslands, which extend approximately 430 miles in central California, paralleling the Sierra Nevada Range to the east and the coastal ranges to the west (averaging 75 miles in longitudinal extent), and stopping abruptly at the Tehachapi Range in the south. Two rivers flow from opposite ends and join around the middle of the valley to form the extensive Sacramento-San Joaquin Delta that flows into San Francisco Bay.

Perennial grasses that were adapted to cool-season growth once dominated the ecoregion. The deep-rooted Purple Needle Grass (Nassella pulchra) was particularly important, although Nodding Needle Grass (Stipa cernua), Wild Ryes (Elymus spp.), Lassen County Bluegrass (Poa limosa), Aristida spp., Crested Hair-grass (Koeleria pyramidata), Deergrass (Muhlenbergia rigens,), and Coast Range Melicgrass (Melica imperfecta) occurred in varying proportions. Most grass growth occurred in the late spring after winter rains and the onset of warmer and sunnier days. Interspersed among the bunchgrasses were a rich array of annual and perennial grasses and forbs, the latter creating extraordinary flowering displays during certain years. Some extensive mass flowerings of the California Poppy (Eschscholzia californica), Lupines (Lupinus spp.), and Exserted Indian Paintbrush (Castilleja exserta) are found in this grassland ecoregion.

Prehistoric grasslands here supported several herbivores including Pronghorn Antelope (Antilocapra americana), elk (including a valley subspecies, the Tule Elk, (Cervus elaphus nannodes), Mule Deer (Odocoileus hemionus), California ground squirrels, gophers, mice, hare, rabbits, and kangaroo rats. Several rodents are endemics or near-endemics to southern valley habitats including the Fresno Kangaroo Rat (Dipodomys nitratoides exilis), Tipton Kangaroo Rat (Dipodomys nitratoides nitratoides), San Joaquin Pocket Mouse (Perognathus inornatus), and Giant Kangaroo Rat (Dipodomys ingens). Predators originally included grizzly bear, gray wolf, coyote, mountain lion, ringtail, bobcat, and the San Joaquin Valley Kit Fox (Vulpes velox), a near-endemic.

The valley and associated delta once supported enormous populations of wintering waterfowl in extensive freshwater marshes. Riparian woodlands acted as important migratory pathways and breeding areas for many neotropical migratory birds. Three species of bird are largely endemic to the Central Valley, surrounding foothills, and portions of the southern coast ranges, namely, the Yellow-billed Magpie (Pica nuttalli), the Tri-colored Blackbird (Agelaius tricolor EN), and Nuttall’s Woodpecker (Picoides nuttallii).

The valley contains a number of reptile species including several endemic or near-endemic species or subspecies such as the San Joaquin Coachwhip (Masticophis flagellum ruddocki), the Blunt-nosed Leopard Lizard (Gambelia sila EN), Gilbert’s Skink (Plestiodon gilberti) and the Sierra Garter Snake (Thamnophis couchii). Lizards present in the ecoregion include: Coast Horned Lizard (Phrynosoma coronatum NT); Western Fence Lizard (Sceloporus occidentalis); Southern Alligator Lizard (Elgaria multicarinata); and the Northern Alligator Lizard (Elgaria coerulea).

There are only a few amphibian species present in the California Central Valley grasslands ecoregion. Special status anuran taxa found here are: Foothill Yellow-legged Frog (Rana boylii NT); Pacific Chorus Frog (Pseudacris regilla); and Western Spadefoot Toad (Pelobates cultripes). The Tiger Salamander (Ambystoma tigrinum) occurs within this ecoregion.

Although many endemic plant species are recognized, especially those associated with vernal pools, e.g. Prickly Spiralgrass (Tuctoria mucronata). A number of invertebrates are known to be restricted to California Central Valley habitats. These include the Delta Green Ground Beetle (Elaphrus viridis CR) known only from a single vernal pool site, and the Valley Elderberry Longhorn Beetle (Desmocerus californicus dimorphus) found only in riparian woodlands of three California counties.

Vernal pool communities occur throughout the Central Valley in seasonally flooded depressions. Several types are recognized including valley pools in basin areas which are typically alkaline or saline, terrace pools on ancient flood terraces of higher ground, and pools on volcanic soils. Vernal pool vegetation is ancient and unique with many habitat and local endemic species. During wet springs, the rims of the pools are encircled by flowers that change in composition as the water recedes. Several aquatic invertebrates are restricted to these unique habitats including a species of fairy shrimp and tadpole shrimp.

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Scrub desert and piedmont are the basic habitats of giant kangaroo rats. They prefer relatively flat homogenous terrain with shrubs and rocks being almost totally absent. Typical habitat is stretches of easily excavated sandy loam covered with annual grasses and herbs.

Terrestrial Biomes: desert or dune ; chaparral

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Habitat and Ecology

Habitat and Ecology
The habitat of giant kangaroo rats consists of gently sloping and level piedmont plains and (formerly) areas supporting saltbush and perennial grasses; habitat now is dominated by introduced annuals, with many shrubs in some areas. The species occupies areas of sparse vegetative cover and well-drained soils and slope generally less than 9% (Williams and Kilburn, 1991) (sometimes up to 22%; USFWS, 1998), often in areas that are heavily grazed by cattle and sheep (Williams and Kilburn, 1991). They prefer semi-arid slopes at the head of draws in barren shrubless areas, with loose, easily diggable, sandy loam soils. Found in underground burrows when inactive. They are absent from areas continuously in dry-land cultivation and from irrigated fields but may recolonize fallow dry-land grain fields if there are colonies on uncultivated land nearby (Williams and Kilburn, 1991). Habitats listed in order of decreasing favorability: 1) annual grassland association in areas with less than five to six inches annual rain, and level to gently sloping ground, 2) alkali desert scrub association in areas with less than five to six inches annual rain, sandy loam soils, and level to gently sloping ground, 3) friable soils of sand, loam, clay loam or gravelly in areas with the above characteristics, and 4) slopes of 10-15 degrees with the above characteristics and located near colonies in more favorable habitats (D. Williams pers. comm.).

Home range is about 60-350sqm. This species is basically solitary and territorial, with strict intrasexual avoidance indicated. In spring, areas around occupied burrows have a more lush growth of herbaceous vegetation than do areas between burrow systems; this growth is eventually removed by grazing by livestock and/or kangaroo rats (Williams and Kilburn, 1991). Digging and feeding activity promote the establishment of exotic weeds, which in turn are a favoured food source (Schiffman, 1994). Giant kangaroo rats feed on seeds, especially those of Lepidium nitidum, oenothera, Bromus rubens, and Erodium cicutarium. They also eat some green herbaceous vegetation and occasionally insects. In some localities. They gather dry grass into "haystacks" to cure, later removing seeds for storage in underground burrows. They also temporarily bury seeds in the ground before storing in burrows. Giant kangaroo rats emerge to forage soon after sunset in spring. They spend a little less than two hours per night above ground actively foraging in spring-summer (Braun, 1985).

Limited data indicate that the reproductive season may extend from January through May (Williams and Kilburn, 1991) (February to June or perhaps later according to Biosystems Analysis, 1989). Gestation lasts about one month. Litter size is three to six (Biosystems Analysis, 1989); average litter size is probably four (Williams and Kilburn, 1991). Young are weaned at four weeks (Matthews and Moseley, 1990).

Systems
  • Terrestrial
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Comments: Habitat consists of gently sloping and level piedmont plains and (formerly) areas supporting saltbush and perennial grasses; habitat now is dominated by introduced annuals, with many shrubs in some areas. The species occupies areas of sparse vegetative cover and well-drained soils and slope generally less than 9% (Williams and Kilburn 1991) (sometimes up to 22%; USFWS 1998), often in areas that are heavily grazed by cattle and sheep (Williams and Kilburn 1991). This kangaroo rat prefers semi-arid slopes at the head of draws in barren shrubless areas, with loose, easily diggable, sandy loam soils. When inactive, it occupies underground burrows. It is absent from areas continuously in dry-land cultivation and from irrigated fields but may recolonize fallow dry-land grain fields if there are colonies on uncultivated land nearby (Williams and Kilburn 1991). Habitats listed in order of decreasing favorability: 1) annual grassland association in areas with less than 5-6 inches annual rain, and level to gently sloping ground, 2) alkali desert scrub association in areas with less than 5-6 inches annual rain, sandy loam soils, and level to gently sloping ground, 3) friable soils of sand, loam, clay loam or gravelly in areas with the above charcateristics, and 4) slopes of 10-15 degrees with the above characteristics and located near colonies in more favorable habitats (D. Williams, pers. comm.). Young are born in burrows.

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Giant kangaroo rats are found in dry areas that receive less than 15 centimetres of rainfall each year, in well-drained sandy soils that are sparsely populated by annual grassland (2) (3).
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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.

Limited data suggest that effective dispersal may extend over several kilometers and that individuals can disperse through highly inhospitable habitat (see USFWS 1998).

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Trophic Strategy

Giant kangaroo rats are granivorous and prefer to eat the seeds and green parts of native desert plants. They are also known to eat grain and the seeds of commercially grown plants if fields are nearby. Food is cured in shallow pits or piles on the ground called 'haystacks.' It is then stored in the central cave of their burrow. They extract all the water they need from these sources.

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Comments: Feeds on seeds, especially those of LEPIDIUM NITIDUM, OENOTHERA, BROMUS RUBENS, and ERODIUM CICUTARIUM. Also eats some green herbaceous vegetation and occasionally insects. In some localities, gathers dry grass into "haystacks" to cure, later removing seeds for storage in underground burrows. Also temporarily buries seeds in ground before storing in burrow.

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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: 6 - 20

Comments: The extant distribution includes more than 100 more or less distinct populations, but most of these represent fragments of a formerly more continuous distribution. There are six major geographic units, each of which could be regarded as a single occurrence or subpopulation.

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Global Abundance

10,000 to >1,000,000 individuals

Comments: Total adult population size is unknown but probably exceeds 100,000 during average conditions. Adult population size varies substantially with drought and plant productivity (USFWS 1998); density ranges from 1 to 110 individuals per hectare (see USFWS 1998).

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General Ecology

Population density is 5-50 per ha (18-69/ha in the larger and denser colonies, Williams and Kilburn 1991). Home range is about 60-350 sq m; strict intrasexual avoidance indicated (basically solitary and territorial). Extant population sizes are small; from fewer than 10 to several hundred individuals (Braun 1985).

In spring, areas around occupied burrows have a more lush growth of herbaceous vegetation than do areas between burrow systems; this growth is eventually removed by grazing by livestock and/or kangaroo rats (Williams and Kilburn 1991).

Digging and feeding activity promote the establishment of exotic weeds, which in turn are a favored food source (Schiffman 1994).

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Life History and Behavior

Behavior

Perception Channels: tactile ; chemical

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Cyclicity

Comments: Emerges to forage soon after sunset in spring. Spends a little less than 2 hours per night above ground actively foraging in spring-summer (Braun 1985).

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Reproduction

Breeding takes place in late winter or early spring. Gestation is 28 to 32 days in length. Anywhere from one to six young are born in a burrow in the spring, three being average. The young are cared for by their mothers and fathers and are weaned in 15 to 25 days. They reach sexual maturity in 60 to 84 days. They then leave the burrow and seek new territories within the colony to dig burrows of their own. Giant kangaroo rats have been known to live up to 9.8 years in the wild.

Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual

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Limited data indicate that the reproductive season may extend from January through May (Williams and Kilburn 1991) (February to June or perhaps later according to Biosystems Analysis 1989). Gestation lasts about 1 month. Litter size is 3-6 (Biosystems Analysis 1989); modal litter size probably is 4 (Williams and Kilburn 1991). Young are weaned at 4 weeks (Matthews and Moseley 1990). Flexible mating system (Hekkala, no date).

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Conservation

Conservation Status

The giant kangaroo rat was designated an endangered species by the California Department of Fish and Game (CDFG) in the early 1980s and is currently restricted to about 2% (under 17,000 hectares) of its historic range. The CDFG, together with the Nature Conservancy and the U.S. Bureau of Land Management, manages the Carrizo Plain Natural Area, which contains ninety percent of remaining habitat. Although protected in this area, giant kangaroo rats will likely be eliminated from all other areas unless habitat loss caused by urban and agricultural development in central California is stopped.

US Federal List: endangered

CITES: no special status

IUCN Red List of Threatened Species: endangered

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IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
B1ab(i,ii,iii)

Version
3.1

Year Assessed
2008

Assessor/s
Linzey, A.V. & NatureServe (Williams, D.F. & Hammerson, G.)

Reviewer/s
Amori, G. (Small Nonvolant Mammal Red List Authority) & Chanson, J. (Global Mammal Assessment Team)

Contributor/s

Justification
Listed as Endangered because its extent of occurrence is less than 5,000 km², its range is severely fragmented, and there is an ongoing decline in the extent of occurrence, area of occupancy, and extent and quality of the species' habitat.

History
  • 2000
    Critically Endangered
  • 1996
    Critically Endangered
    (Baillie and Groombridge 1996)
  • 1996
    Critically Endangered
  • 1994
    Indeterminate
    (Groombridge 1994)
  • 1990
    Indeterminate
    (IUCN 1990)
  • 1988
    Indeterminate
    (IUCN Conservation Monitoring Centre 1988)
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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: Confined to southern California; most populations occupy relatively small areas of suitable habitat; habitat still being lost to various kinds of development; recent protection on the Carrizo Plain has alleviated threats somewhat; lack of appropriate habitat management on conservation lands may be resulting in habitat degradation in some areas.

Other Considerations: Threats have eased significantly since Endangered listing and acquisition of much of extant habitat on Carrizo/Elkhorn plains.

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Current Listing Status Summary

Status: Endangered
Date Listed: 01/05/1987
Lead Region:   California/Nevada Region (Region 8) 
Where Listed: Entire


Population detail:

Population location: Entire
Listing status: E

For most current information and documents related to the conservation status and management of Dipodomys ingens , see its USFWS Species Profile

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Status

Critically Endangered.
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Status

Classified as Critically Endangered (CR) on the IUCN Red List 2007 (1).
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Population

Population
The huge colonies of this species described in historical literature no longer exist. Extant habitat comprises only about 1.8 percent of the historical habitat (Williams, 1992; USFWS, 1998).The extant distribution includes more than 100 more or less distinct populations, but most of these represent fragments of a formerly more continuous distribution. There are six major geographic units, each of which could be regarded as a single occurrence or subpopulation. Total adult population size is unknown but probably exceeds 100,000 during average conditions. Adult population size varies substantially with drought and plant productivity (USFWS, 1998); density ranges from one to 110 individuals per hectare (see USFWS, 1998).

Within the area of currently occupied habitat, populations have expanded and declined with changing weather patterns since 1979; at their peak in 1992 to 1993, there probably were about six to 10 times more individuals than at their low point in spring of 1991, when a majority of the 11,145 hectares probably was uninhabited and most of the rest was inhabited by less than 10 percent of peak numbers (see USFWS, 1998 for sources). Population density is five to 50 per hectare (18-69/ha in the larger and denser colonies, Williams and Kilburn, 1991). Extant population sizes are small; from fewer than 10 to several hundred individuals (Braun, 1985).

Population Trend
Decreasing
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Global Short Term Trend: Decline of 10-30%

Comments: Within the area of currently occupied habitat, populations have expanded and declined with changing weather patterns since 1979; at their peak in 1992 to 1993, there probably were about 6 to 10 times more individuals than at their low point in spring of 1991, when a majority of the 11,145 hectares probably was uninhabited and most of the rest was inhabited by less than 10 percent of peak numbers (see USFWS 1998 for sources).

Global Long Term Trend: Decline of 70 to >90%

Comments: The huge colonies described in historical literature no longer exist. Extant habitat comprises only about 1.8 percent of the historical habitat (Williams 1992, USFWS 1998).

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Threats

Major Threats
The decline is largely a result of conversion of habitat to agricultural uses, combined with additional loss of habitat to industrial uses (e.g., petroleum exploration and extraction) and urbanization, and population reductions and extirpations from rodenticide use (aimed at California ground squirrel and historically at kangaroo rats) (Williams, 1992; USFWS, 1998). Possibly excessive livestock grazing may have contributed to the decline in some areas (livestock may crush near-surface burrows and compete for food with kangaroo rats) (see USFWS, 1998). Between 1972 and 1980 most of the remaining habitat was converted from native vegetation to cultivated agricultural crops due in part to an abundance of irrigation water supplied by recently completed water delivery systems.

More recently, the conversion of habitat to agricultural uses has slowed substantially, but urban and industrial developments, petroleum and mineral exploration and extraction, new energy and water conveyance facilities, and construction of communication and transportation infrastructures continue to destroy habitat and increase the threats to the species by reducing and further fragmenting populations (USFWS, 1998). Habitat degradation due to lack of appropriate habitat management on conservation lands, especially lack of grazing or fire to control density of vegetation (including shrubs) may be a threat (Williams and Germano, 1993).
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Degree of Threat: Medium

Comments: The decline is largely a result of conversion of habitat to agricultural uses, combined with additional loss of habitat to industrial uses (e.g., petroleum exploration and extraction) and urbanization, and population reductions and extirpations from rodenticide use (aimed at California ground squirrel and historically at kangaroo rats) (Williams 1992, USFWS 1998). Possibly excessive livestock grazing may have contributed to the decline in some areas (livestock may crush near-surface burrows and comptete for food with kangaroo rats) (see USFWS 1998). Between 1972 and 1980 most of the remaining habitat was converted from native vegetation to cultivated agricultural crops due in part to an abundance of irrigation water supplied by recently completed water delivery systems.

More recently, conversion of habitat to agricultural uses has slowed substantially, but urban and industrial developments, petroleum and mineral exploration and extraction, new energy and water conveyance facilities, and construction of communication and transportation infrastructures continue to destroy habitat and increase the threats to the species by reducing and further fragmenting populations (USFWS 1998). Habitat degradation due to lack of appropriate habitat management on conservation lands, especially lack of grazing or fire to control density of vegetation (including shrubs) may be a threat (Williams and Germano 1993).

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Population numbers of the giant kangaroo rat plummeted during the 20th Century (1), mainly as a result of habitat loss as desert areas were converted to agriculture (7). Over 95 percent of the former range of this species has been lost due to a combination of overgrazing, cultivation, mining operations and the introduction exotic plants (1).
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Management

Conservation Actions

Conservation Actions
D. ingenswas listed as Endangered by both the California Fish and Game Commission (in 1980) and the United States Fish and Wildlife Service (in 1987). Habitat is protected to varying degrees at Carrizo Plain National Monument, U.S. Department of Energy Naval Petroleum Reserves in western Kern County, and certain BLM lands. Parcels in the Lokern area of western Kern County have been protected by the California Energy Commission, California Department of Fish and Game, and The Nature Conservancy.

Habitat for three of the six regional populations (Cuyama Valley, Kettleman Hills, and San Juan Creek Valley) include no public or conservation lands; all are small and vulnerable to extirpation from demographic and random catastrophic events (e.g., drought, flooding, fire), and inappropriate land uses that would degrade or destroy habitat (USFWS, 1998).

Future conservation actions require an adequate understanding of compatible land uses and management prescriptions that provide optimum habitat conditions (Williams and Germano, 1993). Data should be collected on demography, dispersal, and reproduction, as well as the status of populations occurring on private lands in the Cuyama Valley, San Juan Creek area, and Ciervo/Tumey Hills. See USFWS (1998) for specific protection, management, and monitoring needs.
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Biological Research Needs: Data are needed on demography, dispersal, and reproduction.

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Global Protection: Several (4-12) occurrences appropriately protected and managed

Comments: Habitat is protected to varying degrees at Carrizo Plain National Monument, U.S. Department of Energy Naval Petroleum Reserves in western Kern County, and certain BLM lands. Parcels in the Lokern area of western Kern County have been protected by the California Energy Commission, California Department of Fish and Game, and The Nature Conservancy.

Habitat for three of the six regional populations (Cuyama Valley, Kettleman Hills, and San Juan Creek Valley) include no public or conservation lands; all are small and vulnerable to extirpation from demographic and random catastrophic events (e.g., drought, flooding, fire), and inappropriate land uses that would degrade or destroy habitat (USFWS 1998).

Needs: Key to protection is an adequate understanding of compatible land uses and management
prescriptions that provide optimum habitat conditions (Williams and Germano 1993).

See USFWS (1998) for specific protection, management, and monitoring needs.

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Conservation

This species is listed as Endangered by the California Fish and Game Commission and the United States Fish and Wildlife Service (1). A Recovery Plan has been developed in an effort to secure the future survival of this species (8), and populations are protected within the Carrizo Plan Natural Heritage Reserve and a number of Federal lands (1).
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Relevance to Humans and Ecosystems

Benefits

The burrow complexes of adults create very soft heaps of dirt that can collapse under the pressure exerted by livestock or a human. Because of this, sheep and cattle tend to avoid areas containing burrows; therefore, land inhabited by the rats is deemed less valuable to ranchers.

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While providing no direct economic benefits, giant kangaroo rats help maintain the desert habitat in which they live by feeding on and collecting seeds. Kangaroo rats in general were popularized in Walt Disney's film, The Living Desert. As an easily recognizable species of kangaroo rat, the giant kangaroo rat possesses a degree of charisma and is seen as adding aesthetic value to the region.

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Wikipedia

Giant kangaroo rat

The giant kangaroo rat, Dipodomys ingens, is an endangered species of heteromyid rodent endemic to California.[2]

Description[edit]

Dipodomys ingens, the giant kangaroo rat, is one of over 20 species of kangaroo rats, which are small members of the rodent family. The giant kangaroo rat is the largest of the kangaroo rats, measuring about 15 cm (6 in.) in length, including its long, tufted tail. It is tan or brown in color. Like other kangaroo rats it has a large head and large eyes, and long, strong hind legs with which it can hop at high speeds.

The Giant Kangaroo Rat has been recently added to the endangered species list due to its habitat being severely reduced. Data was collected on its foraging behavior and social structure. Traps baited kangaroo rats with oats in them for four weeks in the summer. The animals were captured, tagged with tracking devices and set free. Results show that significantly fewer males were captured. This could have been due to the time of year at which the experiment was tested. Females were found to be more social. Studies also showed that the kangaroo rat’s den is the area in which the animal spends the most time.

Habitat[edit]

The giant kangaroo rat lives on dry, sandy grasslands and digs burrows in loose soil. It lives in colonies, and the individuals communicate with each other by drumming their feet on the ground. These foot thumping signals range from single, short thumps to long, drawn out “footrolls” that can average over 100 drums at 18 drums per second. These audible signals serve both as a warning of approaching danger, as a territorial communication, and to communicate mating status.

In the spring and summer, individuals generally spend less than two hours of the night foraging above ground. They are very territorial and never leave their den for more than 15 minutes per day. The giant kangaroo rat then stores the seeds in a larder for later eating and gives birth to a litter of 1 to 7 babies, with an average of 3 per litter. It communicates with potential mates by sandbathing, where the giant kangaroo rat rubs its sides in sand, leaving behind a scent to attract mates. They live for only 2–4 years.

This species was declared endangered on both the federal and California state levels in the 1980s. It inhabits less than a mere 2% of its original range and can now be found only in isolated areas west of the San Joaquin Valley, including the Carrizo Plain, the Elkhorn Plain, and the Kettleman Hills. The giant kangaroo rat, like many other rodent species, lost much of its habitat as the Central Valley fell under agricultural use. Much information still needs to be obtained regarding their basic biology and compatibility with various land uses before clear directives can be made. Besides some projects currently underway in the Carrizo Plain National Monument, studies need to be conducted on populations whose range overlaps with private lands.

Different seasons also affect the mating of the Giant Kangaroo Rat. During the summer, the male rats go out of their comfort zones and mate with neighboring female rats in order to expand their family. During the winter, the males stay in their original burrow and stay with females as well. Researchers use tables and pictographs to show the size of home ranges from the male and female rats during the winter and summer seasons. By taking a select number of male and female kangaroo rats from each season and studying their mating patterns, studies are able to determine whether the home-ranges overlap or not. It has been proven that the smaller the amount of rats in the study, the larger the overlapping of burrows. Also the larger amount of rats used for the study had their burrows spaced out. Therefore it is easy to believe that the amount of rats used for the study determined the home-ranges. If there is a large amount of rats being studied, then the burrows formed in order to mate will be spaced further apart by comparison to the space made by the small amount of rats used for the study. Because one of the studies used 7 kangaroo rats and another used over 20, there is more of a reason for the study of 20+ rats to have spread out burrows and the study of 7 rats to have overlapping burrows.

Endangered Giant Kangaroo Rat (Dipodomys ingens)) populations have become more dispersed and less numerous over time. This can have major side effects to the genetic diversity of the species. The D. ingens populations only cover about 3% of the territory of what they historically used to live in. Agricultural development has severely impacted the habitats of the D. ingens, and restricted it to several small isolated areas. Because of this, the D. ingens is at risk for genetic drift and inbreeding within smaller populations. The D. ingens lives in metapopulation structures due to their habitats being taken over by humans. They are divided into several small remnant populations that are unable to disperse over larger areas because of topographical limitations. This is a larger problem for northern subpopulations of D. ingens than those who live in the south. D. ingens is believed to be polygynous (one male, multiple females) but a common ratio between male and female partners has not yet been found. The study showed that translocation was a successful method for increasing diversity and population size of D. ingens.

According to information vetted by Los Padres Forest Watch, the GKR is a keystone species in the Carrizo Plain and probably elsewhere in the San Joaquin Valley. It provides food for predators and creates burrow systems used by other animals. It is important to recognize that GKR viability is not simply a matter of one obscure species, at all, but rather an integral cornerstone[citation needed] of the entire affected ecosystem. In the Carrizzo Plain, just outside the National Monument, GKR is in jeopardy due to several proposed massive solar installations as well as a mining proposal linked to the CVSR project[citation needed].

References[edit]

  1. ^ Linzey, A.V. & NatureServe (Williams, D.F. & Hammerson, G.) (2008). Dipodomys ingens. In: IUCN 2008. IUCN Red List of Threatened Species. Retrieved 13 January 2009.
  2. ^ Patton, J. L. (2005). "Family Heteromyidae". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. p. 846. ISBN 978-0-8018-8221-0. OCLC 62265494. 
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Names and Taxonomy

Taxonomy

Comments: See Good et al. (1997) for information on genetic structure of extant populations of D. ingens. See Williams and Kilburn (1991) for a review of the possible relationships between D. ingens and other Dipodomys.

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