Lagomorpha

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Lagomorphs[1]
Temporal range: Late Paleocene–Recent
Oryctolagus cuniculus Tasmania 2.jpg
European rabbit in Tasmania
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)

Lagomorpha range.png
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[edit]

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.[1]

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.[2]

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.[3] More recent examination of the fossil evidence suggests that 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).[4] 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.[5]

Characteristics[edit]

Lagomorphs are similar to other mammals in many ways, in that they all have fur, bear live young, have four limbs, lactate, etc. They differ in that they have a mixture of "primitive" and "advanced" traits.

Differences between Lagomorphs and other mammals[edit]

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.[6][7] The two pairs of incisors are an advanced trait.[citation needed][further explanation needed]

Similar to the Rodentia, Chiroptera, and Insectivora, they lack a Corpus callosum.[8]

Differences between families of Lagomorphs[edit]

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.[9]

Pikas[edit]

American pika in Alberta

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, and almost no tail. 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 and 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: the rock dwellers aggressively maintain 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. As they do not hibernate, they make "haypiles" of dried vegetation which they collect and carry back to their homes to store for use during winter.[9]

Hares[edit]

Scrub hare in South Africa

Hares, members of genus Lepus of family Leporidae, are medium size mammals native to all the continents except South America, Australia and Antarctica. North American jackrabbits 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 young are born fully furred and active. Hares eat plant material including stripping the bark off tree trunks. They are preyed upon by large mammalian carnivores and birds of prey.[10]

Rabbits[edit]

Marsh rabbit in Florida

Rabbits, members of family Leporidae outside Lepus, are generally rather smaller than hares and include the rock hares and the hispid hare. They are native to Europe, parts of Africa, Central and Southern Asia, North America and much of South 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 (nests). Some of the burrowing species 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.[11]

Distribution[edit]

Lagomorphs are widespread around the world and inhabit every continent except Antarctica. However, they are not found in the southern cone of South America, in the West Indies, Greenland, Indonesia or Madagascar, nor on 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.[12]

Biology[edit]

Like other herbivores, Lagomorphs 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 that 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.[13]

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.[14] 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.[7]

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 pikas 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.[12]

Classification[edit]

References[edit]

  1. ^ a b c Hoffman, R. S.; Smith, A. T. (2005). "Order Lagomorpha". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. pp. 185–211. ISBN 978-0-8018-8221-0. OCLC 62265494. 
  2. ^ Hoffman, R. S.; Smith, A. T. (2005). Prolagus sardus in Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. ISBN 978-0-8018-8221-0. 
  3. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 285. ISBN 1-84028-152-9. 
  4. ^ Rose, Kenneth David (2006). The Beginning of the Age of Mammals. The Johns Hopkins University Press. p. 315. ISBN 0-8018-8472-1. 
  5. ^ Savage, RJG, & Long, MR (1986). Mammal Evolution: an illustrated guide. New York: Facts on File. pp. 128–129. ISBN 0-8160-1194-X. 
  6. ^ Best, T. L., Henry, T. H. (1994-06-02). "Lepus arcticus". Mammalian Species 457 (457): 1–9. doi:10.2307/3504088. ISSN 0076-3519. JSTOR 3504088. OCLC 46381503. 
  7. ^ a b Smith, Andrew T. "Lagomorph". Encyclopedia Britannica. Retrieved 2013-08-13. 
  8. ^ [1]. Accessed November 18, 2013.
  9. ^ a b Smith, Andrew T. "Pika". Encyclopedia Britannica. Retrieved 2013-08-15. 
  10. ^ Smith, Andrew T. "Hare". Encyclopedia Britannica. Retrieved 2013-08-15. 
  11. ^ Smith, Andrew T. "Rabbit". Encyclopedia Britannica. Retrieved 2013-08-15. 
  12. ^ a b Klappenbach, Laura. "Hares, Rabbits and Pikas". About.com. Retrieved 2013-08-14. 
  13. ^ "Exploring a Rabbit's Unique Digestive System". Rabbits for Dummies. Retrieved 2013-08-14. 
  14. ^ Burton, Maurice (1971). The Observer's Book of British Wild Animals. Frederick Warne & Co. pp. 109–112. ISBN 9780723215035. 
  15. ^ The Paleobiology Database Lagomorpha entry Accessed on 13 May 2010