Leporidae (/ləˈpɔːrɪdiː,-daɪ/) is the family of rabbits and hares, containing over 70 species of extant mammals in all. The Latin word Leporidae means "those that resemble lepus" (hare). Together with the pikas, the Leporidae constitute the mammalianorderLagomorpha. Leporidae differ from pikas in that they have short, furry tails and elongated ears and hind legs.
The common name "rabbit" usually applies to all genera in the family except Lepus, while members of Lepus (almost half the species) usually are called hares. Like most common names, however, the distinction does not match current taxonomy completely; jackrabbits are members of Lepus, and members of the genera Pronolagus and Caprolagus sometimes are called hares.
Various countries across all continents except Antarctica and Australia have indigenous species of Leporidae. Furthermore, rabbits, most significantly the European rabbit, Oryctolagus cuniculus, also have been introduced to most of Oceania and to many other islands, where they pose serious ecological and commercial threats.
Leporids are small to moderately sized mammals, adapted for rapid movement. They have long hind legs, with four toes on each foot, and shorter fore legs, with five toes each. The soles of their feet are hairy, to improve grip while running, and they have strong claws on all of their toes. Leporids also have distinctive, elongated and mobile ears, and they have an excellent sense of hearing. Their eyes are large, and their night vision is good, reflecting their primarily nocturnal or crepuscular mode of living.[2]
Leporids are all roughly the same shape and fall within a small range of sizes with short tails, ranging in overall length from the 21 cm (8 in) long Tres Marias cottontail to the 76 cm (30 in) long desert hare. Female leporids are almost always larger than males, which is unusual among terrestrial mammals.
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Both rabbits and hares are almost exclusively herbivorous (although some Lepus species are known to eat carrion),
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feeding primarily on grasses and herbs, although they also eat leaves, fruit, and seeds of various kinds. Easily digestible food is processed in the gastrointestinal tract and expelled as regular feces. But in order to get nutrients out of hard to digest fiber, leporids ferment fiber in the cecum (in the GI tract) and then expel the contents as cecotropes, which are reingested (cecotrophy). The cecotropes are then absorbed in the small intestine to utilize the nutrients.[6]
They have adapted to a remarkable range of habitats, from desert to tundra, forests, mountains, and swampland. Some rabbits dig burrows for shelter, the exact form of which varies between species. Other rabbits do not dig burrows but use forms, usually under a bush. Hares rarely dig shelters of any kind, instead using forms, and their bodies are more suited to fast running than to burrowing.[2]
Reproduction
Leporids are typically polygynandrous, and some have highly developed social systems. Their social hierarchies determine which males mate. Rabbits are induced ovulators (ovulate during mating).
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Species nesting below ground tend to have lower predation rates and have larger litters.[9]
The gestation period in leporids varies from around 28 to 50 days, and is generally longer in the hares. This is in part because young hares (called leverets) are born precocial (eyes and ears open, fully furred), while young rabbits (called kits) are born altricial (eyes and ears closed, no fur).[2] Higher latitudes correspond to shorter gestation periods.[10] Leporids can have several litters a year, which can cause their population to expand dramatically in a short time when resources are plentiful. Gestation period and litter size correspond to predation rates as well.
Evolution
Serengetilagus praecapensis skull, Naturkundemuseum, Berlin
The oldest known leporid species date from the late Eocene, by which time the family was already present in both North America and Asia. Over the course of their evolution, this group has become increasingly adapted to lives of fast running and leaping. For example, Palaeolagus, an extinct rabbit from the Oligocene of North America, had shorter hind legs than modern forms (indicating it ran rather than hopped) though it was in most other respects quite rabbit-like.[11] Two as yet unnamed fossil finds—dated ~48 Ma (48 million yr) ago (from China) and ~53 Ma (53 million yr) ago (India)—while primitive, display the characteristic leporid ankle, thus pushing the divergence of Ochotonidae and Leporidae yet further into the past.[12]
The cladogram is from Matthee et al., 2004, based on nuclear and mitochondrial gene analysis.[13]
^Ralls, Katherine (June 1976). "Mammals in Which Females are Larger Than Males". The Quarterly Review of Biology. 51 (2): 245–276. doi:10.1086/409310. PMID785524. S2CID25927323.
^Bell, Diana; Smith, Andrew T. (2006) [copyright 2001]. "Lagomorphs". In Macdonald, David; Norris, Sasha (eds.). The Encyclopedia of Mammals. London: The Brown Reference Group. p. 695. ISBN0-681-45659-0.
^Chapman, Joseph A. (1 September 1984). "Latitude and Gestation Period in New World Rabbits (Leporidae: Sylvilagus and Romerolagus)". The American Naturalist. 124 (3): 442–445. doi:10.1086/284286. JSTOR2461471. S2CID83584955.
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