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Lepus insularisblack jackrabbit

By Joseph R. Mejia

Geographic Range

Lepus insularis is endemic to Espiritu Santo Island in the Gulf of California, Mexico, from sea level to 300 meters elevation. It has also been introduced to nearby Pichilinque Island (Thomas and Best, 1994).

Habitat

This species, also known as black jackrabbits, is found all over Espiritu Santo Island but is most abundant in the valleys and adjoining lower slopes of the hills. Espiritu Santo Island is a waterless volcanic island characterized by rocky hills and low mountains. Black jackrabbits favor places scattered with arid tropical shrubs, cacti, and other plants since the upper slopes are rocky and barren (Thomas and Best, 1994).

Physical Description

Black jackrabbits have a characteristic glossy black head, usually with a few white hairs on the middle of the crown and grayish hairs near the ears and eyes. The rest of the upper pelage, including the top of the tail, is glossy black with fine grizzling of dark cinnamon. The cinnamon color predominates ventrally. A black line extends along the inner sides of the hind feet from the toes to slightly above the heel. The soles of the feet are heavily padded. Average body size is 574 mm and average tail length is 96 mm. Like other hares, females are usually larger than males (Dixon et al., 1983).

  • Sexual Dimorphism
  • female larger
  • Average length
    574 mm
    22.60 in

Reproduction

Little is known about the reproductive patterns of black jackrabbits. Mating season is usually restricted to the milder seasons of the year. It typically lasts from January to August. Two or three litters are produced by each female during the spring and summer. Litter size is normally three to four. Gestation usually lasts 41 to 43 days. In contrast to rabbits, young black jack "rabbits" are precocial. They are well furred at birth, their eyes are open, and they can move about soon after birth. Weaning lasts only a few days, at which time the mother abandons the young (Nowak, 1983).

  • Breeding interval
    These animals can breed up to three times per year.
  • Breeding season
    Breeding occurs from January to August.
  • Average number of offspring
    3-4
  • Range gestation period
    0.03 to 0.03 days

Behavior

Black jackrabbits are solitary animals. Rather than digging and occupying burrows, they rest and take shelter in shallow depressions made in soil or vegetation. There, black jackrabbits resemble a short, charred stump among the gray-green vegetation and bare slopes and are extraordinarily conspicuous, even when motionless. Black jackrabbits are mainly nocturnal. During the day, they spend most of their time in the shade under bushes. During the most active part of the mating season, the males lose their customary caution and are abroad fighting with other males and pursuing females. Fighting consists of boxing with the fore feet or kicking with the hind feet. When mating, females may be quite seriously mauled by their overenergetic consorts who bite and kick them (Nowak, 1983).

Communication and Perception

Food Habits

Lepus insularis is an herbivore. Grasses are the preferred food choice of black jackrabbits, but these animals have also been known to consume tree bark when other food supplies are not readily available. Since Espiritu Santo Island is a virtually waterless island, all of the required water is obtained through ingested vegetation (Nowak, 1983).

  • Plant Foods
  • leaves
  • wood, bark, or stems

Economic Importance for Humans: Positive

According to local fisherman, humans from nearby Pichilinque Island hunt black jackrabbits for food. Although its fur is not particularly valuable nor durable, it has been used to manufacture felt (Nowak, 1983).

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

During the dry season when green vegetation is scarce, hares will gnaw on bark. As a result, orchards and plantations suffer at this time because the hares girdle young stems and cause plants to die (Bourne, 1997).

Conservation Status

The only predatory mammal on Espiritu Santo Island is Bassariscus astutus, which probably never hunts even young black jackrabbits. A few American kestrels and caracaras are the only birds of prey known on the island, thus the natural enemies of black jackrabbits are few. Since Espiritu Santo Island may never be inhabited by humans, black jackrabbits seem in no immediate danger and the population is stable. However, it may be wise to consider establishing another population on some nearby island (Thomas and Best, 1994).

Other Comments

Populations of Lepus californicus in what appears to be the same climate, vegetation, and other physical surroundings on the mainland exhibit no sign of melanism. The isolation of L. insularis on Espiritu Santo Island, combined with the virtual absence of predatory birds and mammals, has apparently removed selection pressure favoring cryptic coloration.

Lepus insularis is a close relative of L. californicus of the nearby peninsula of Baja California. The species-level status of L. insularis has been questioned. However, in a multivariate comparison, there was a distinct separation based upon cranial characters.

The genus name Lepus is derived from the Latin lepus, meaning hare. The specific epithet insularis comes from the Latin word insula indicating the island range. Additional names include black hare and Espiritu Santo jackrabbit (Thomas and Best, 1994).

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Joseph R. Mejia (author), University of Michigan-Ann Arbor.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

herbivore

An animal that eats mainly plants or parts of plants.

island endemic

animals that live only on an island or set of islands.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

saltatorial

specialized for leaping or bounding locomotion; jumps or hops.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

young precocial

young are relatively well-developed when born

References

Bourne, J. 1997. Control of Rabbits and Hares. Alberta Agriculture, Food and Rural Development. http://www.agric.gov.ab.ca/

Dixon, K. R., J. A. Chapman, G. R. Willner, D. E. Wilson, and W. Lopez-Forment. 1983. The New World Jackrabbits and Hares (genus Lepus). Acta Zoologica Fennica, 174: 7-10.

Nowak, R. M. and J. L. Paradiso. 1983. Walker's Mammals of the World. Fourth Edition, Volume II. Johns Hopkins University Press, Baltimore.

Thomas, H. H. and T. L. Best. 1994. Mammalian Species, No. 465, American Society of Mammalogists. pp. 1-3.

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