Lagomorpha

Lagomorphs Temporal range:
Oryctolagus cuniculus 'European Rabbit'.
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Infraclass:	Eutheria
Magnorder:	Boreoeutheria
Superorder:	Euarchontoglires
(unranked):	Glires
Order:	Lagomorpha Brandt, 1855
Families
Leporidae Ochotonidae Prolagidae (extinct)
Range of Lagomorpha

The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two living families: the Leporidae (hares and rabbits) and the Ochotonidae (pikas). The name of the order is derived from the Greek lagos (λαγός, "hare") and morphē (μορφή, "form"). There are about eighty species of lagomorph which include thirty species of pika, twenty species of rabbits and cottontails, and thirty species of hares.

Taxonomy and evolutionary history

Other names used for this order which are now considered synonymous include: Duplicidentata - Illiger, 1811; Leporida - Averianov, 1999; Neolagomorpha - Averianov, 1999; Ochotonida - Averianov, 1999; Palarodentia - Haeckel, 1895.

The extinct family Prolagidae is represented by a single species, the Sardinian pika Prolagus sardus, fossils of which are known from Sardinia, Corsica and nearby small islands. It may have survived until about 1774.

These mammals often resemble rodents (order Rodentia) and were classified as a superfamily in that order until the early 20th century. Even after that time it was common to consider the lagomorphs as distant relatives of the rodents, but in fact they merely bear a superficial resemblance to them. Both lagomorphs and rodents have teeth that grow continuously throughout their lives but it is now appreciated that they acquired this trait independently as the result of their similar modes of life. Both groups are animals that have a fibrous, vegetable diet and their teeth are continually being worn away, a case of convergent evolution. Lagomorphs are now considered to be a completely separate order from rodents.

The evolutionary history of the lagomorphs is still not well understood. Until recently, it was generally agreed that Eurymylus, which lived in eastern Asia and dates back to the late Paleocene or early Eocene, was an ancestor of the lagomorphs. More recent examination of the fossil evidence suggests the lagomorphs may have instead descended from Anagaloidea, also known as mimotonids, while Eurymylus was more closely related to rodents (although not a direct ancestor). The leporids first appeared in the late Eocene and rapidly spread throughout the Northern Hemisphere; they show a trend towards increasingly long hind limbs as the modern leaping gait developed. The pikas appeared somewhat later in the Oligocene of eastern Asia.

Characteristics

Lagomorphs differ from rodents in that they have four incisors in the upper jaw (not two, as in the Rodentia) and they are almost strictly herbivorous unlike rodents, many of which will eat both meat and vegetable matter. However, they resemble rodents in that their incisor teeth grow continuously throughout their lives, thus necessitating constant chewing on fibrous food to prevent the teeth from growing too long.

Rabbits and hares move by jumping, pushing off with their strong hind legs and using their forelimbs to soften the impact on landing. Pikas lack certain skeletal modifications present in rabbits and hares such as a highly arched skull, an upright posture of the head, strong hind limbs and pelvic girdle, and long limbs.

Pikas

American pika in Alberta

The pikas, family Ochotonidae, are small mammals native to mountainous regions of western North America and Central Asia. They are mostly about 15 cm (6 in) long and have greyish-brown silky fur, small rounded ears, almost no tail and their four legs are nearly equal in length. Some species live in scree, making their homes in the crevices between broken rocks, while others construct burrows in upland areas. The rock dwelling species are typically long-lived, solitary, have one or two litters of a small number of young each year and have stable populations. The burrowing species in contrast, are short-lived, gregarious and have multiple large litters during the year. These species tend to have large swings in population size. The social behaviour of the two groups also differs with the rock dwellers aggressively maintaining scent-marked territories while the burrowers live in family groups, interact vocally with each other and defend a mutual territory. Pikas are diurnal and are active early and late in the day during hot weather. They feed on all sorts of plant material. They do not hibernate so they make "haypiles" of dried vegetation which they collect and carry back to their homes to store for use during winter.

Hares

Scrub hare in South Africa

The hares, family Leporidae, are medium size mammals native to all the continents except Antarctica. The jackrabbits of North America are really hares. Species vary in size from 40 to 70 cm (16 to 28 in) in length and have long powerful back legs, and ears up to 20 cm (8 in) in length. Although usually greyish-brown, some species turn white in winter. They are solitary animals and several litters of young are born during the year in a form, a hollow in the ground amongst dense vegetation. The leverets are fully furred and active from birth and soon create their own little forms. Hares eat plant material including stripping the bark off tree trunks. They are preyed on by large mammalian carnivores and birds of prey.

Rabbits

Marsh rabbit in Florida

The rabbits, family Leporidae, are generally rather smaller than hares and include the rock hares and the hispid hare. They are native to Europe, Central and Southern Asia and temperate part of North America. They inhabit both grassland and arid regions. They vary in size from 20 to 50 cm (8 to 20 in) and have long, powerful hind legs, shorter forelegs and a tiny tail. The colour is some shade of brown, buff or grey and there is one black species and two striped ones. Domesticated rabbits come in a wider variety of colours. Although most species live and breed in burrows, the cottontails and hispid hares have forms. Some of the burrowing forms are colonial but most are solitary or may feed together in small groups. Rabbits play an important part in the terrestrial food chain, eating a wide range of forbs, grasses and herbs and being part of the staple diet of many carnivorous species.

Distribution

Lagomorphs are widespread around the world and inhabit every continent except Antarctica. They are not however found in parts of South America, in the West Indies, in Greenland, Indonesia or Madagascar, nor in many islands. Although they are not native to Australia, humans have introduced them there and they have successfully colonized many parts of the country and caused disruption to native species.

Biology

Lagomorphs are herbivores and like other herbivores have to deal with a bulky diet in which the cell walls are composed of cellulose, a substance which mammalian digestive enzymes are unable to break down. Despite this, lagomorphs have developed a way of extracting maximum nourishment from their diet. First they bite off and shred plant tissues with their incisors and then they grind the material with their molars. Digestion continues in the stomach and small intestine where nutrients are absorbed. After that, certain food remains get diverted into the caecum, a blind-ended pouch. Here they are mixed with bacteria, yeasts and other micro-organisms which are able to digest cellulose and turn it into sugar, a process known as hindgut fermentation. Other faecal matter passes along the colon and is excreted in the normal way as small, dry pellets. About four to eight hours after the meal, the contents of the caecum pass into the colon and are eliminated as soft, moist pellets known as cecotropes. These are immediately eaten by the lagomorph which can thus extract all the remaining nutrients in the food.

Many lagomorphs breed several times a year and produce large litters. This is particularly the case in species that breed in underground, protective environments such as burrows. The altricial young are born naked and helpless after a short gestation period and the mother can become pregnant again almost immediately after giving birth. The mothers are able to leave these young safely and go off to feed, returning at intervals to feed them with their unusually rich milk. In some species, the mother only visits and feeds the litter once a day but the young grow rapidly and are usually weaned within a month. Hares live above ground and their litters are born in "forms" concealed among tussocks and scrub. They have a strategy to prevent predators from tracking down their litter by following the adults' scent. They approach and depart from the nesting site in a series of immense bounds, sometimes moving at right angles to their previous direction. The young are precocial and a small number are born after a longer gestation period, already clad in short fur and able to move around.

Many species of lagomorphs, particularly the rabbits and the pikas, are gregarious and live in colonies whereas hares are generally solitary species. The rabbits and picas rely on their holes as places of safety when danger threatens but hares rely on their long legs, great speed and jinking gait to escape from predators. Despite these defensive devices, lagomorphs form an important part of the diet of carnivorous mammals, birds of prey and owls.

Classification

• Order Lagomorpha Brandt 1885
  • Family Leporidae Fischer de Waldheim 1817 (rabbits and hares)
    • Subfamily † Archaeolaginae
      • Genus †Archaeolagus Dice 1917
      • Genus †Hypolagus Dice 1917
      • Genus †Notolagus Wilson 1938
      • Genus †Panolax Cope 1874
    • Subfamily Leporinae Trouessart 1880
      • Genus †Alilepus Dice 1931
      • Genus Brachylagus
      • Genus Bunolagus
      • Genus Caprolagus Blyth 1845
      • Genus Lepus Linnaeus 1758
      • Genus Nesolagus Forsyth Major 1899
      • Genus Oryctolagus Lilljeborg 1874
      • Genus †Nuralagus Lilljeborg 1874
      • Genus Pentalagus Lyon 1904
      • Genus †Pliolagus Kormos 1934
      • Genus †Pliosiwalagus Patnaik 2001
      • Genus Poelagus
      • Genus †Pratilepus Hibbard 1939
      • Genus Pronolagus Lyon 1904
      • Genus Romerolagus Merriam 1896
      • Genus †Serengetilagus Dietrich 1941
      • Genus Sylvilagus Gray 1867
    • Subfamily †Palaeolaginae Dice 1929
      • Tribe †Dasyporcina Gray 1825
        • Genus †Coelogenys Illiger 1811
        • Genus †Agispelagus Argyropulo 1939
        • Genus †Aluralagus Downey 1968
        • Genus †Austrolagomys Stromer 1926
        • Genus †Aztlanolagus Russell & Harris 1986
        • Genus †Chadrolagus Gawne 1978
        • Genus †Gobiolagus Burke 1941
        • Genus †Lagotherium Pictet 1853
        • Genus †Lepoides White 1988
        • Genus †Nekrolagus Hibbard 1939
        • Genus †Ordolagus de Muizon 1977
        • Genus †Paranotolagus Miller & Carranza-Castaneda 1982
        • Genus †Pewelagus White 1984
        • Genus †Pliopentalagus Gureev & Konkova 1964
        • Genus †Pronotolagus White 1991
        • Genus †Tachylagus Storer 1992
        • Genus †Trischizolagus Radulesco & Samson 1967
        • Genus †Veterilepus Radulesco & Samson 1967
        • Tribe incertae sedis
          • Genus †Litolagus Dawson 1958
          • Genus †Megalagus Walker 1931
          • Genus †Mytonolagus Burke 1934
          • Genus †Palaeolagus Leidy 1856
  • Family Ochotonidae Thomas 1897 pikas
    • Genus †Alloptox Dawson 1961
    • Genus †Amphilagus Tobien 1974
    • Genus †Bellatona Dawson 1961
    • Genus †Cuyamalagus Hutchison & Lindsay 1974
    • Genus †Desmatolagus Matthew & Granger 1923
    • Genus †Gripholagomys Green 1972
    • Genus †Hesperolagomys Clark et al. 1964
    • Genus †Kenyalagomys MacInnes 1953
    • Genus †Lagopsis Schlosser 1894
    • Genus Ochotona Link 1795
    • Genus †Ochotonoides Teilhard de Jardin & Young 1931
    • Genus †Ochotonoma Sen 1998
    • Genus †Oklahomalagus Dalquest et al. 1996
    • Genus †Oreolagus Dice 1917
    • Genus †Piezodus Viret 1929
    • Genus †Russellagus Storer 1970
    • Genus †Sinolagomys Bohlin 1937
    • Genus †Titanomys von Meyer 1843
  • Family †Prolagidae Gureev, 1962 (Sardinian Pika and other related extinct pika-like lagomorphs)
    • Genus †Prolagus Pomel 1853
  • Family incertae sedis
    • Genus †Eurolagus Lopez Martinez 1977
    • Genus †Hsiuannania Xu 1976
    • Genus †Hypsimylus Zhai 1977
    • Genus †Lushilagus Li 1965
    • Genus †Shamolagus Burke 1941