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Lagomorpha

Lagomorpha (Duplicidentata; infraclass Eutheria, cohort Glires) An order that comprises the families Eurymylidae (extinct forms), Ochotonidae (pikas), and Leporidae (rabbits, cottontails, and hares). The lagomorphs are believed to have diverged from a primitive eutherian stock at the same time as, or soon after, the rodents, so that similarities between lagomorphs and rodents may be very superficial. There is a single record from the late Palaeocene of Mongolia, but the order is not encountered again until the late Eocene, after which it spread widely in N. America and Eurasia. Ancestors of modern lagomorphs, very similar to modern forms, lived during the Oligocene. The incisors grow continually, but to either side of those of the upper jaw there is a small, peg-like incisor that gave the order its old name of Duplicidentata. There is a wide diastema between the incisors and the cheek teeth. The premolars and molars have sharp edges and are used for cutting rather than grinding, the upper teeth biting outside the lower teeth. The nostrils can be closed and are surrounded by naked skin which may be covered by surrounding fur. There are four or five digits on the hind limbs and five on the fore limbs. The tail is reduced and may not be visible externally. Like some rodents, lagomorphs pass food twice through the alimentary canal (caecotrophy).

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Lagomorphs

Lagomorphs

Families of lagomorphs

Rabbits and hares of North America

The American pika

Economic importance

Resources

Lagomorphs are herbivorous mammals such as rabbits, hares, and pikas in the order Lagomorpha. Because they exploit similar ecological niches, lagomorphs and rodents (order Rodentia) are rather similar in many aspects of their morphology and behavior. However, these orders are also different in important respects, and each represents an ancient evolutionary lineage.

One distinguishing feature of the lagomorphs is the two pairs of upper incisor teeth, one set being relatively small and located behind the larger pair. These incisors grow throughout the life of lagomorphs, and are completely covered with enamel; the larger pair has rather deep, vertical grooves. The incisors are used for clipping vegetation, and they are separated from the high-crowned cheek teeth, used for grinding food, by a rather wide gap, known as a diastema.

In addition, lagomorphs have five toes on the forefeet and four on the hind, dense, short fur, covering a thin, fragile skin that tears rather easily. The tail of these animals is short or absent. All lagomorphs are herbivores. Their major food is succulent leaves and herbaceous stems of a wide range of plant species. However, twigs and buds are also eaten, especially by northern species during the winter. Lagomorphs have a specialized enlarged portion of the large intestine known as the caecum, which acts as a fermentation chamber for the digestion of the cellulose in their bulky food of herbage and woody shoots.

Families of lagomorphs

The 60 lagomorph species of are included in two families. The Leporidae consists of rabbits and hares, familiar animals that have long ears and large hind feet. The Ochotonidae or pikas have relatively short ears and small hind feet.

Rabbits and hares are well known animals to most people. The natural distribution of this group of animals is extensive, occurring worldwide except for Madagascar, Australia, New Zealand, and various Pacific islands. However, humans have deliberately introduced rabbits to these other places, in particular the European rabbit (Oryctolagus cuniculus ) and the European hare (Lepus europaeus ). Both of these species typically become pests in their introduced habitats, where their abundance is not well controlled by predators.

Rabbits and hares have long ears, and large, strong, hind legs with big feet, structures that are well adapted to leaping, or to more leisurely hopping. Most species are either crepuscular, meaning they are

most active around dawn and dusk, or they are nocturnal, being active at night. The young of rabbits are born naked and blind in an underground burrow, while baby hares are born fully furred, with their eyes open in a surface nest. Young rabbits are initially quite helpless, while baby hares are relatively independent and can run soon after birth.

Rabbits and hares produce two types of fecal pellets. One type is soft and green, consists of partially digested food, and is produced at night. These soft pellets are refected, or reingested by the animal, and are swallowed without chewing. Eating its own droppings (coprophagy) allows for a twice-through process of digestion and assimilation of nutrients from the cecum, which is sited after the stomach and small intestine. This is similar in some respects to the habit of ruminant animals of regurgitating their cud, which is chewed again, and then reswallowed. The other type of fecal pellet of rabbits and hares is brown and drier, is not eaten again, and is produced during the day.

Pikas or conies are small animals in the genus Ochotona that live in two disjunct parts of the world in central Asia and Japan, and in western North America. This is an unusual distribution, and it suggests that the pikas probably migrated to North America from Asia via the Bering land bridge, exposed when

sea levels were lowered during the Pleistocene glaciation, which ended about 15,000 years ago. The two populations of pikas became separated when sea levels rose again, and eventually evolved in isolation into distinct species.

Pikas have short ears and small feet, and they lack an external tail, although close examination of their skeletons reveals a vestigial tail structure. The color of the pelage of pikas varies from blackish to cinnamon-brown. Pikas are diurnal, or active during the day. Their habitat is alpine tundra, where these animals typically live in rocky piles, or bouldery talus at the base of cliffs.

Rabbits and hares of North America

North America is home to 15 species of rabbits and hares. All of these are rather abundant within their range. These medium-sized herbivores are important sources of food for many species of predatory birds and mammals, and they are also commonly hunted by people.

The most familiar native rabbit in much of North America is the eastern cottontail (Sylvilagus floridanus ), a relatively small species that typically weighs about 2.4-3.3 pounds (1.1-1.5 kg), with females being slightly larger than males. The common name of this rabbit comes from its tail, which is white underneath and is held erect when running. The eastern cottontail is common in shrubby thickets in the vicinity of forest, orchards, and meadows. This rabbit is abundant across southeastern North America, extending into Mexico. The eastern cottontail has significantly expanded its range during the past century, probably because of improved habitat that has resulted from various human influences, especially the conversion of closed forests into certain types of agricultural and forestry ecosystems.

The cottontail rabbit is active all year, eating foliage of a wide range of plants when available, and buds and twigs of woody plants during the winter. Cottontails begin to mate during the winter, and the females (does) bear their first litters of two to seven young in the springtime, and may have three or more litters per year. This sort of explosive reproductive potential is typical of rabbits and hares, and it is not surprising that so many predators depend on these fertile animals as food.

Other common North American rabbits include the mountain cottontail (S. nuttalli) of mountainous regions of the west, the desert cottontail (S. auduboni) of arid regions of the southwest, the brush rabbit (S. bachmani) of Oregon and California, and the swamp and marsh rabbits (S. aquaticus and S. palustris, respectively) of wet habitats in the southeast. The latter two species take readily to the water and swim well. All of these rabbits are abundant, and are hunted over much of their range.

The most widespread hare in North America is the snowshoe or varying hare (Lepus americana), which is found from the low-arctic tundra through much of the northern United States. This species is dark brown during the summer, but a camouflaged white in winter. This species goes through more-or-less cyclic variations of abundance in northern parts of its range, which are tracked by the populations of some of its predators, such as lynx (Lynx rufus).

The arctic hare (L. arcticus) occurs throughout the northern tundra regions of North America, extending as far as the limits of land on the northern islands of Canada and Greenland. The white-tailed jackrabbit (L. townsendii) occurs in semi-desert and dry prairies of central-western North America, while the black-tailed jackrabbit (L. californicus) is more southwestern in its distribution. The European hare (L. europaeus ) has been introduced to parts of the eastern United States and Canada, and is the largest lagomorph in North America, weighing as much as 10 pounds (4.5 kg).

The American pika

The American pika (Ochotona princeps) occurs through much of the Rocky Mountains, from southern Alaska, through British Columbia, and the northwestern United States. The American pika is about 7.5-7.9 inches (19-20 cm) long, and weighs 6.1-8.2 oz (175-235 g).

Pikas are active during the day. When they are not foraging, they spend much of their time surveying their alpine domain for danger, usually from the top of a prominent rock. When a potential predator is seen to approach, the pika emits loud bleats, which warn other animals of the danger. However, as with many types of warning calls of small mammals and birds, it is very difficult to locate the source of the bleating noise, so the pika is not readily revealing its location. If a human sits quietly nearby, most pikas will carefully approach to appraise the nature of the intruder.

Pikas do not hibernate, remaining active under the alpine snowpack. They store fodder for their long winters, as large haystacks of dried forage, each about 0.25 m3 in volume, and typically located beneath an overhanging rock that provides shelter from the weather.

Pikas are prey for a wide range of alpine predators, including the golden eagle, buteo hawks, foxes, and mustellids such as weasels. Pikas are especially vulnerable to predators when they are foraging in alpine meadows, beyond the immediate safety of the rocks and crevices in which these animals typically find shelter and protection. However, some smaller predators, such as the ermine (Mustela erminea), can follow pikas through their pathways and tunnels among the rocks.

Economic importance

Wild rabbits and hares of all species are a favorite class of small game hunted by many people for the pot and as sport. These animals are rather fecund and their populations can be quite productive, and they can therefore be harvested in large numbers. Millions of these animals are shot and snared each year in North America. They are hunted mostly for their meat, because the skins of these animals are fragile and tear easily, and therefore the fur has little commercial value.

Rabbit and hare populations of have increased greatly in many areas, because human activities have eliminated many lagomorph predators substantially improved the quality of their habitats. Most rabbits and hares of forested regions are early- and mid-successional species. Consequently, these animals benefit from many types of forest disturbances associated with human activities, such as the harvesting of trees in forestry, and some types of agricultural developments. Rabbits and hares are also typically abundant on agricultural or residential lands that have been abandoned, and are in a shrubby stage of the succession back to forest.

Rabbits and hares often do significant damage in gardens by eating vegetables, and by damaging shrubs of various species, sometimes killing them by eating the bark at the base of these woody plants. This damage can be controlled using fencing, or by protecting the bases of the shrubs with chemical repellants or metal collars. Hares can do considerable damage in forestry plantations, by clipping small seedlings of conifers or other planted trees.

The domestic rabbit has been developed through cultural selection from the old-world or European rabbit (Oryctolagus cuniculus). This rabbit often lives colonially and digs extensive systems of underground tunnels and dens, known as warrens, the largest of which can cover more than 25 acres (1 ha). The old-world rabbit was originally native to southwestern Europe and northwestern Africa. However, this rabbit is now much more widespread in the wild, because it has been introduced throughout most of western

KEY TERMS

Cultural selection Selection by humans of individual animals having some desirable, genetically based traits, leading to evolution at the population level. This selective breeding eventually results in the development of distinctive varieties of domesticated species of plants and animals. See entry on evolution.

Lagomorphs A widespread mammalian order, consisting of two families, the pikas or Ochotonidae, and the rabbits and hares or Leporidae.

Myxomatosis An infectious, usually fatal viral disease of rabbits. Myxomatosis is sometimes introduced by humans to control the populations of rabbits when they become pests. Symptoms of the disease include swelling of the mucous membranes, and the development of skin tumors.

Refection The habit of rabbits and hares of reingesting their soft, green fecal pellets. Refection allows for a twice-through passage of food, which contributes to more efficient digestion and absorption of nutrients.

Succession A process of ecological change, involving the progressive replacement of earlier communities with others over time, and generally beginning with the disturbance of a previous type of ecosystem.

Europe and Britain, the Americas, Australasia, and many other places. The European rabbit often causes severe damage in its introduced habitats by developing large, feral populations that overgraze the vegetation. A deadly disease known as myxomatosis has been introduced in Australia and other countries to try to reduce the population of this invasive rabbit. Although this pathogen generally achieves initial reductions in the abundance of rabbits, the surviving animals are relatively resistant to the disease, so that longer-term control is not generally realized.

Because of selective breeding, domestic rabbits are now available in a wide range of genetically based varieties, which differ in size, shape, color, length of fur, and other characteristics. Many domestic rabbits are raised specifically for food, others are used as laboratory animals, and many others are kept as pets.

Resources

BOOKS

Banfield, A.W.F. The Mammals of Canada. Toronto, ON, Canada: University of Toronto Press, 1974.

McBride, G. Rabbits and Hares. U.K.: Whittet Press, 1988.

Thompson, H.V. and C.M. King. The European Rabbit. History and Biology of a Successful Colonizer. Oxford, U.K.: Oxford University Press, 1994.

OTHER

The Pied Piper. Rabbits <http://www.the-piedpiper.co.uk/th14.htm> (accessed December 2, 2006).

University of Michigan, Animal Diversity Web. Order Lagomorpha (Hares, Pikas, and Rabbits) <http://animaldiversity.ummz.umich.edu/site/accounts/information/Lagomorpha.html> (accessed December 2, 2006).

Bill Freedman

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"Lagomorphs." The Gale Encyclopedia of Science. . Encyclopedia.com. 11 Dec. 2017 <http://www.encyclopedia.com>.

"Lagomorphs." The Gale Encyclopedia of Science. . Encyclopedia.com. (December 11, 2017). http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/lagomorphs

"Lagomorphs." The Gale Encyclopedia of Science. . Retrieved December 11, 2017 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/lagomorphs