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Lepus californicus bennettii

(Black-Tailed Jackrabbit)

Interesting Facts

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Common Names

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Common Names in English:

Black-Tailed Jackrabbit

Description

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Habitat

The black-tailed-jackrabbit occupies many diverse habitats , but primarily is found in arid regions supporting shortgrass habitats. Jackrabbits typically are not found in high grass or dense brush where it is difficult for them to locomote, and the openness of open scrub habitat probably is preferred over dense chaparral . Jackrabbits are common in grasslands that are overgrazed by cattle and they are well adapted to using low-intensity agricultural habitats (Lechleitner 1959). In fact, to a point , drought and overgrazing may create better habitat for black-tailed-jackrabbits (Bronson and Tiemeir 1959). The openness of such habitat allows jackrabbits to escape predators and humans by fast, often long-distance sprints (S. Montgomery, pers. comm. 1999). In Riverside County, black-tailed jackrabbits are found in most areas that support annual grassland, Riversidean sage scrub, alluvial fan sage scrub, Great Basin sagebrush, chaparral, disturbed habitat, and agriculture. Jackrabbits also are observed in southern willow scrub and juniper woodland (MWD and RCHCA 1995). Black-tailed-jackrabbits typically do not burrow, but take shelter at the base of shrubs in shallow depressions called forms. However, during the summer in the Mojave Desert, jackrabbits may use desert tortoise (Gopherus agassizii) burrows to escape the heat (Costa et al. 1976) and Smith (1990) observed jackrabbits using burrows in the winter in northern Utah, concluding that it was an anti-predator strategy.

Black-tailed-jackrabbits locations in the MSHCP data base include a broad variety of vegetation and land cover mapping types . The majority of locations (68 of 271) were in chaparral (including red shank chaparral), 61 were in non-native grassland, 55 were in sage scrub (Riversidean sage scrub, Diegan coastal sage scrub, and Great Basin sagebrush scrub), 47 were in residential/urban/exotic, 32 were in crop lands/grove/orchard, and 5 were in oak woodlands (including Engelmann oak woodland).

Typically found at an altitude of 0 to 964 meters (0 to 3,163 feet).[1]

Biology

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Diet

Black-tailed-jackrabbits are considered generalist herbivores (Johnson and Anderson 1984). In semidesert and desert rangelands in New Mexico, Nevada and Idaho, for example, grasses and forbs are the largest components of their diet , with shrubs less important (Johnson and Anderson 1984; Hayden 1966; Wansi et al. 1992). However, their diet shifts between season , locations, years, and vegetation types , suggesting that jackrabbits are opportunistic foragers. This is an important trait in a species that occupies a broad range of habitats and climates.

Reproduction

Black-tailed-jackrabbits exhibit a promiscuous breeding pattern , with females accepting the first interested male (Best 1996). They are induced ovulators; i.e. , copulation is required to stimulate ovulation. Breeding can occur throughout the year, but shows stronger seasonality in some regions, with more northern latitudes exhibiting shorter, distinct seasons (Bronson and Tiemeir 1958; Feldhamer 1979; Wagner and Stoddart 1972). The length of the breeding season appears to be related to the production of herbaceous vegetation (Lechleitner 1959). In Butte County, California, Lechleitner (1959) observed slight seasonality, and found reproductive males and young in every month of the year. Females in his study area were pregnant every month, but showed a peak pregnancy period from January to August. In a Kansas population of black-tailed-jackrabbits, Bronson and Tiemeir (1958) found that breeding occurred in January through August; a 220-day breeding season. Felhamer (1979) recorded a breeding season from mid-February to mid-June in Idaho. The peak breeding season in northern Utah also was about January to August (Wagner and Stoddart 1972). Litter sizes vary seasonally, with larger litters later in the breeding season (Bronson and Tiemeir 1959; French et al. 1965; Lechleitner 1959). French et al. (1965) also suggested that the shorter breeding seasons in more severe northern climates are compensated for by larger litters than populations in southern latitudes with longer breeding seasons. Litters of 1-7 have been recorded (Bronson and Tiemeir 1958; Feldhamer 1979; French et al. 1965) and average litter sizes were 4.9 and 3.3 in southeastern Idaho, 2.5 in Kansas, 2.3 to 2.5 in California, and 1.8 and 2.2 in Arizona. Bronson and Tiemeir (1958) estimated that an adult female in Kansas could produce 3.8 litters per year and about 9.9 offspring, without correction for resorption of the litters (i.e., probably a slight overestimate). Lechleitner (1959) estimated productivity of about 10 young per female per year in California. Felhamer estimated productivity of 2.5 litters per season and 10.2 young/female/season in Idaho. The number of young produced per year is about the same throughout the range of the black-tailed-jackrabbit, but populations in the north achieve similar productivity with fewer, but larger litters because of the shorter breeding season.

The gestation period of the black-tailed-jackrabbit is approximately 43 days (41-47 days) (Best 1996; Dunn et al. 1984). In response to environmental stressors (e.g. , blizzards), prenatal mortality appears to be high, with 16% pre-implantation resorption and up to 30% post-implantation loss (Feldhamer 1979). Young in northern California are weaned by three weeks (Lechleitner 1959). Breeding by young of the year may be uncommon (e.g., Felhamer 1979; Lechleitner 1959). Males produce sperm at 5-7 months of age and in Butte County, California jackrabbits reach adult weight by about 32 weeks of age (Lechleitner 1959). French et al. (1965) found that population increases were followed by decreases in the breeding season and an overall decline in population productivity (i.e., a decline in fertility ), while population declines were followed by increases in the breeding season and productivity. They concluded that black-tailed-jackrabbits exhibit density-dependent reproduction .

Survival: Survival rates generally appear to be low and population turnover high in black-tailed-jackrabbits (Feldhamer 1979; French et al. 1965; Lechleitner 1959). For example, French et al. (1965) observed that two-thirds of the cohort in southeastern Idaho turnover from the population each week during the winter due to mortality and dispersal and only 3.5% of the cohort remained after one year. Feldhamer (1979) noted a similar mortality rate in black-tailed-jackrabbits in Idaho, with estimates of 91% for first-year mortality, 94% by two years of age, and 98% by three years of age. In a northern Utah population, the March-to-October mortality rate was 56% of the population, the October-to-March rate was 57%, and birth-to-October rate for juveniles was 58% (Wagner and Stoddart 1972). Monthly mortality rates were about 13-16%. Wagner and Stoddart determined that the mortality rates for juveniles and adults were about the same. They also determined that coyotes (Canis latrans) are a primary cause of mortality by noting the high correlation between coyote populations and adult mortality and documenting kills of radiotelemetered animals. Other predators of jackrabbits include bobcats (Felis rufus), American badger (Taxidea taxus), golden eagle (Aquila chrysaetos), red-tailed hawk (Buteo jamaicensis), northern harrier (Circus cyaneus), and great-horned owl (Bubo virginianus) (Wagner and Stoddart 1972). In many areas of the black-tailed-jackrabbit’s range, hunting, road and landowner kills, and predation are the major cause of mortality (Bronson and Tiemeir 1959). Best (1996) concluded that jackrabbits probably do not live much longer than seven years in the wild.

Populations are thought to fluctuate widely on 7 to 10 year cycles (Smith 1990; Wagner and Stoddart 1972).

Dispersal: Typical dispersal distances may be relatively short, but black-tailed-jackrabbits are capable of dispersing long distances . French et al. (1965) recorded most dispersal distances at less than 0.25 mile , but 18% of juveniles dispersed greater distances and one individual dispersed 28 miles in 17 weeks. Most seasonal movements involve short distances and may be related to food availability (Bronson and Tiemeir 1959).

Behavior

Daily Activity: Black-tailed-jackrabbits primarily are nocturnal . They typically are non-burrowers and take refuge under shrubs in depressions or forms during the day. In a study of jackrabbits in the Mojave Desert, Costa et al. (1976) observed that animals became active within 30 minutes of sunset and retreated to daytime forms between dawn and sunrise. During the night they spent between 3.5 and 4.5 hours foraging , with bouts being intermittent . Non-feeding time was spent moving about and standing in open areas. Activity was reduced during the winter, but there were no detectable seasonal patterns of nocturnal activity related to season . Diurnal behavior was markedly different. During moderate temperature conditions, jackrabbits spent the entire day in their refuges. On cold winter mornings, jackrabbits basked in the sunlight, presumably helping them to keep warm and reduce energy requirements. On hot summer days, jackrabbits became restless, and moved to find shade or enter burrows dug by tortoises or by the jackrabbit itself. They retreat to burrows only during the hottest part of the day. Smith (1990) observed jackrabbits using burrows in the winter in northern Utah and concluded that it was an anti-predator strategy. Smith (1990) also found that males were more active than females in the breeding season (winter and spring ).

Survival: Survival rates generally appear to be low and population turnover high in black-tailed-jackrabbits (Feldhamer 1979; French et al. 1965; Lechleitner 1959). For example, French et al. (1965) observed that two-thirds of the cohort in southeastern Idaho turnover from the population each week during the winter due to mortality and dispersal and only 3.5% of the cohort remained after one year. Feldhamer (1979) noted a similar mortality rate in black-tailed-jackrabbits in Idaho, with estimates of 91% for first-year mortality, 94% by two years of age, and 98% by three years of age. In a northern Utah population, the March-to-October mortality rate was 56% of the population, the October-to-March rate was 57%, and birth-to-October rate for juveniles was 58% (Wagner and Stoddart 1972). Monthly mortality rates were about 13-16%. Wagner and Stoddart determined that the mortality rates for juveniles and adults were about the same. They also determined that coyotes (Canis latrans) are a primary cause of mortality by noting the high correlation between coyote populations and adult mortality and documenting kills of radiotelemetered animals. Other predators of jackrabbits include bobcats (Felis rufus), American badger (Taxidea taxus), golden eagle (Aquila chrysaetos), red-tailed hawk (Buteo jamaicensis), northern harrier (Circus cyaneus), and great-horned owl (Bubo virginianus) (Wagner and Stoddart 1972). In many areas of the black-tailed-jackrabbit’s range , hunting, road and landowner kills, and predation are the major cause of mortality (Bronson and Tiemeir 1959). Best (1996) concluded that jackrabbits probably do not live much longer than seven years in the wild.

Populations are thought to fluctuate widely on 7 to 10 year cycles (Smith 1990; Wagner and Stoddart 1972).

Socio-Spatial Behavior: Home ranges of the black-tailed-jackrabbit are variable, but typically range from 20 to 140 hectares (ha) (Best 1996). French et al. (1965), however, recorded ranges of only 16 ha (40 acres ) in southeastern Idaho. On the other hand, Smith (1990) used radiotelemetry to estimate home ranges in northern Utah and found ranges of less than 100 ha to 300 ha. Smith also found that home ranges typically were sexually monomorphic ; ranges were only slightly larger for males compared to females. There was substantial overlap in home ranges among individuals, with no relationship to sex or age-group. Smith also found that jackrabbits tend to shift their home range over time, with the shifts occurring gradually. There also were no sex or age-group effects in home range shifts. These rather random spacing patterns are consistent with their promiscuous mating system . The apparent density and spacing of the black-tailed-jackrabbit may be related to changes in the distribution of food resources . For example, Bronson and Tiemeir (1959) found that in Kansas changes in food availability was a primary factor in population densities. Drought and overgrazing depleted food resources, resulting in aggregations of black-tailed-jackrabbits in low areas where moisture collected and near crops . After rains, black-tailed-jackrabbits dispersed because food was more plentiful. Population densities in this study varied from 1 rabbit/4-6 acres when food was plentiful to 1.4/acre when food was scarce. Johnson and Anderson (1984) concluded that jackrabbits in Idaho were found in higher densities in areas that had large amounts of grassland and that this distribution was related to diet rather than nesting cover . Because of shifting distributions and densities in relation to food resources, French et al. (1965) concluded that estimating population densities is difficult.

Taxonomy

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Similar Species

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Best (1996) noted a diploid chromosome number of 48, but no data are available on subjects such as genetic diversity, etc. that would be helpful in conservation planning and management.

Members of the genus Lepus

ZipcodeZoo has pages for 58 species and subspecies in this genus:

L. alleni (Antelope Jack Rabbit) · L. alleni alleni (Antelope Jack Rabbit) · L. americanus (Snowshoe Rabbit) · L. americanus americanus (Snowshoe Hare) · L. americanus klamathensis (Snowshoe Hare) · L. americanus seclusus (Bighorn Mountain Snowshoe Hare) · L. americanus tahoensis (Sierra Nevada Snowshoe Hare) · L. americanus washingtonii (Washington Snowshoe Hare) · L. arcticus (Arctic Hare) · L. arcticus arcticus (Arctic Hare) · L. brachyurus (Japanese Hare) · L. brachyurus brachyurus (Japanese Hare) · L. californica (Black-Tailed Jack Rabbit) · L. californicus (Black-Tailed Jack Rabbit) · L. californicus bennettii (Black-Tailed Jackrabbit) · L. californicus californicus (Black-Tailed Jack Rabbit) · L. callotis (Beautiful-Eared Jack Rabbit) · L. callotis callotis (Beautiful-Eared Jack Rabbit) · L. callotis gaillardi (White-Sided Jackrabbit) · L. capensis (European Hare) · L. capensis capensis (Brown Hare) · L. castroviejoi (Broom Hare) · L. comus (Yunnan Hare) · L. coreanus (Korean Hare) · L. corsicanus (APPENINE HARE) · L. europaeus (European Brown Hare) · L. fagani (Ethiopian Hare) · L. flavigularis (Tehuantepec Jack Rabbit) · L. granatensis (Iberian Hare) · L. granatensis granatensis (Granada Hare) · L. habessinicus (Abyssinian Hare) · L. hainanus (Chinese Pinyin) · L. insularis (Espiritu Santo Jackrabbit) · L. mandshuricus (Manchurian Hare) · L. microtis (African Savanna Hare) · L. nigricollis (Black-Napped Hare) · L. nigricollis nigricollis (Indian Hare) · L. oiostolus (Woolly Hare) · L. oiostolus oiostolus (Woolly Hare) · L. oistolus (Woolly Hare) · L. othus (Beringian Hare) · L. othus othus (Alaskan Hare) · L. peguensis (Siamese Hare) · L. saxatilis (Savannah Hare) · L. saxatilis saxatilis (Scrub Hare) · L. sinensis (Chinese Hare) · L. sinensis sinensis (Chinese Hare) · L. starcki (Ethiopian Highland Hare) · L. tibetanus (Desert Hare) · L. timidus (Eurasian Arctic Hare) · L. timidus timidus (Arctic Hare) · L. tolai (Tolai Hare) · L. townsendi (White-Tailed Jack Rabbit) · L. townsendii (White-Tailed Jack Rabbit) · L. townsendii campanius (White-Tailed Jackrabbit) · L. townsendii townsendii (Western White-Tailed Jackrabbit) · L. victoriae (African Savanna Hare) · L. yarkandensis (Yarkland Hare)

More Info

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Further Reading

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Notes

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Contributors

Identifiers

Footnotes

  1. Mean = 318.260 meters (1,044.160 feet), Standard Deviation = 268.640 based on 46 observations. Altitude information for each observation from British Oceanographic Data Centre. [back]
Last Revised: 7/16/2012