Lagomorpha

Order Lagomorpha is represented by two living families: Ochotonidae (pikas), and Lep-oridae (rabbits and hares). The thirteen genera and eighty-two living species of lagomorphs are terrestrial herbivores. Their natural distributions covered most major land areas except Antarctica, southern South America, Madagascar, the Australian-New Guinea region, New Zealand, and many islands. One species now occurs worldwide through human introduction. Certain species are exploited by humans for food, recreational hunting, clothing, and medical and commercial research; others are detested for their exploitation of crops and grazing lands, and their deleterious impact upon the indigenous fauna.

Preceding the nineteenth century, lago-morphs were arranged as a suborder within Order Rodentia, but by the early 1920s lago-morphs and rodents were placed in different orders. At different times they have also been allied with marsupials, primates, insectivores, and artiodactyls. Currently the circle has closed, and rodents are again regarded as the closest living relatives of lagomorphs. The first true lagomorphs have been found in

Eocene sediments, so the origin of the group probably extends into the Paleocene.

Lagomorphs share a suite of morphological features setting them apart from other mammals. All have long, dense, and soft fur, haired foot soles, and a tail that is short and furred in rabbits and hares but not visible externally in pikas. There are five digits on each front and hind foot (the first is very small in rabbits and hares, so each hind foot appears to have four digits). The testes are located anterior to the base of the penis, instead of behind as in most other mammals. Facial and back regions of the skull are composed of thin, highly perforated bone (fenestrated). All lagomorphs have one pair of ever-growing lower incisors but two pairs of ever-growing uppers, the second situated just behind the first (a third pair is present at birth but is quickly lost). Between incisors and premolars is a long, toothless gap (diastema) without canine teeth. The cheek teeth (premolars and molars) are high-crowned and without roots (ever-growing). Cheek teeth occlude in such a way that food can be masticated by sometimes vertical, but usually transverse (side-to-side) movements on only one side of the jaw at a time. Jaw movement is powered by two sets of large jaw muscles: the masseter, responsible for vertical movement;

and the pterygoids, important for side-to-side motion. The clavicle (shoulder bone) is prominent in pikas but hardly developed in rabbits and hares. Configuration of the elbow joint (tongue and groove articulation of ulna and humerus) restricts movement of anterior limbs to a front-and-back-plane (no side-to-side or rotary movements are possible). Fecal pellets are reingested (coprophagy).

Living lagomorph species are classified into two families. Ochotonidae (pikas) consists of Ochotona, with twenty-five living species; and Prolagus, with one species endemic to Mediterranean islands (Corsica, Sardinia, and smaller nearby islands) that is now extinct but persisted until possibly the late 1700s. These two genera are remnants of a recorded fossil diversity of twenty-four extinct genera. Ochotonids are rooted in Late Eocene sediments in Asia; Oligocene in Europe and North America; Early Miocene in Africa; and Middle Miocene in the Mediterranean region. By the Miocene, pikas were living in Eurasia, North America, Africa, and the Mediterranean area. Living pikas are not found in western Europe or Africa, but they do occur in western North America, Eastern Europe, and most of Asia south to Iran, Afghanistan, Pakistan, northern India, Nepal, and Sikkim, and, until historical times, on some Mediterranean islands.

Leporidae (rabbits and hares) consist of eleven recent genera and fifty-five living species; thirty-one extinct genera are represented by fossils. The earliest records are from Eocene sediments in Asia, Africa, and North America. Leporids first appear in the Mediterranean region during the Miocene and have been in Central and South America since the Pleistocene. Their present natural distribution includes most major land masses in the Old and New Worlds. The European rabbit (Oryctolagus cuniculus) was originally endemic to the Iberian Peninsula and southern France

The desert cottontail rabbit is one of the fifty-five living species of rabbits and hares. (D. Robert and Lorri Franz/Corbis)

but has now been introduced on all continents (except Antarctica, Asia, and many islands) and has been domesticated throughout its introduced range. Several species of hares (Lepus) have been introduced to regions where they do not occur naturally.

Pikas are small, with a head and body averaging 200 mm, and weighing 125 to 400 gm. They have short limbs and small, rounded ears. Fur ranges from grayish to buffy brown. Pikas are most active in early morning and evening but may forage at all hours. North American pikas live in talus slopes where they shelter in chambers and crevices among the rocks. They forage in adjacent meadows, cutting grasses, sedges, and forbs that are hauled to the talus, where it is stacked until dry and then stored within the rocky labyrinths for later use. Some Eurasian species also live in talus and rock-strewn terraces, but others inhabit plains, desert-steppes, and forests where they excavate burrows for shelter. Pikas do not hibernate, even though they live in regions subject to long, cold winters.

Body size of leporids ranges from 275 mm (weighing up to 462 gm) in the pygmy rabbit (Brachylagus idahoensis) to about 700 mm (weighing up to 5 kg) in some of the larger species of hares (Lepus). Fur color ranges from gray to brown, and two species (Nesolagus) are patterned gray and white. Front legs are much shorter than the elongate hind legs. Ears are short in some species but very long in others, and those species also have very long hind feet. Leporids inhabit savannas, deserts, steppes, tundra, boreal to tropical forests, alpine meadows, and a variety of regrowth formations. Scampering species usually shelter and seek safety from predators in burrows, but swift and strong runners shelter in surface depressions (forms) and rely upon their speed to escape predators. Two species of Lepus in the southeastern United States are amphibious.

Lagomorphs are an important element in natural ecosystems. In temperate and boreal regions some leporids undergo population cycles of impressive abundance alternating with extreme scarcity, often influencing the population densities of their predators.

—Mary Ellen Holden

See also: Alien Species; Artiodactyls; Deserts and Semiarid Scrublands; Food Webs and Food Pyramids; Herbivory; Mammalia; Primates; Rodents

Bibliography

Anderson, Sydney, and J. Knox Jones, Jr., eds. 1984. Orders and Families of Recent Mammals of the World. New York: John Wiley and Sons; Chapman, Joseph A., and John E. C. Flux, eds. 1990. Rabbits, Hares and Pikas. International Union for the Conservation of Nature and Natural Resources (IUCN) Gland, Switzerland: IUCN Publications; Hoffman, Robert S.

1993. "Order Lagomorpha." In Mammal Species of the World, 2d ed., edited by Don E. Wilson and DeeAnn M. Reeder, pp. 807-827. Washington, DC: Smithsonian Institution Press; McKenna, Malcolm C., and Susan K. Bell. 1997. Classification of Mammals above the Species Level. New York: Columbia University Press; Nowak, Ronald M. 1999. Walker's Mammals of the World, 6th ed. Vol. 2. Baltimore: Johns Hopkins University Press; Vaughan, Terry A., James M. Ryan, and Nicholas J. Czaplewski. 2000. Mammalogy, 4th ed. Orlando, FL: Harcourt; Wilson, Don E., and Sue Ruff, eds. 1999. The Smithsonian Book of North American Mammals. Washington, DC: Smithsonian Institution Press.

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