Caviidaecavies

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The Caviidae is a family of rodents that occurs over most of South America. It includes two subfamilies: the Caviinae, the cavies and the familiar guinea pigs; and the Dolichotinae, the Patagonian hares or maras. There are a total of five genera and fourteen species of caviids.

Caviidae is a diverse family morphologically, including small forms such as species of Galea, which weigh up to 600 grams, and large forms such as Dolichotis, which may weigh up to 16 kilograms. The members of the two subfamilies are quite distinct. The caviines have short limbs and ears and robust bodies, whereas the Patagonian hares are characterized by a rabbit-like body form with long ears and thin, long limbs. The nails of the caviines are short and either sharp or blunt; those of Dolichotis are hooflike on the hindfeet and clawlike on the forefeet.

Cavies belonging to the great South American radiation of hystricognath rodents. This group arrived in South America probably in the early Oligocene, well before most other rodents, and diversified extensively. Nevertheless, the lower jaws of caviids are scarcely hystricognathous, appearing to have almost reverted to a sciurognathous condition. The mandibles have a well-developed masseteric crest running high along the sides, separated from the toothrow by a deep groove. The arrangement of their masseters and the areas of the cranium from which they originate ( zygomatic arch, infraorbital canal, rostrum, etc.) are strongly hystricomorphous. The skulls of caviids have well-developed bullae that are noticeably enlarged in some species, and a substantial paroccipital process.

Obvious dental characteristics distinguish the members of Caviidae from the members of other families of South American rodents. The dental formula for the family is 1/1, 0/0, 1/1, 3/3 = 20. The teeth of caviids are flat-crowned, hypsodont, and ever-growing ( rootless). All teeth except the third molar have a simple pattern of two prisms, formed by one labial and one lingual reentrant fold. The rows of cheekteeth converge strongly anteriorly. Karyotypes are also highly conserved amongst the members of this family, with 2n=64. The tail is vestigial in all members of caviids.

Among the most abundant and widely distributed of all South American hystricomorph rodents, caviids are found in habitats ranging from marshy, tropical floodplain to dry, rocky, high-altitude meadows. Some species live in open grasslands, others are found in semiarid grasslands, barren zones, or in the dry steppes and high mountains of Peru and Argentina. Generally caviids are not found in dense jungle. They range form Venezuela south to southern Patagonia; they are absent from Chile and some parts of the Amazon basin.

Caviids are usually diurnal or crepuscular and do not hibernate. They shelter in burrows that they dig or that are left by other animals. They are generally social, occurring in pairs or in groups. Some have complex social hierarchies. Members of this family may breed year-round; they have a gestation period (50 to 70 days) that is short for the group of rodents to which caviids belong. Young are well developed at birth and reach sexual maturity early.

Caviids eat primarily plant material, but there is considerable variation in dietary specializations within the family. For example, Microcavia eats leaves and fruits that it may obtain by climbing trees, whereas Cavia does not climb and eats only grasses.

Members of the family Caviidae first appear in the fossil record in the mid-Miocene, 20 million years ago. The group underwent a radiation 5 to 2 million years ago, in the Pliocene; eleven genera are represented from that time.

Cavies and guinea pigs have benefited humans for thousands of years. The domestic guinea pig, Cavia porcellus, now found worldwide in captivity, has been bred for meat for more than three thousand years in South America. During the period of the Inca Empire, from 1200 to 1532, selective breeding resulted in many strains of the guinea pig. Since the mid-1800s this animal has been used for laboratory research. Today it is raised for meat by the natives of Ecuador, Peru, and Bolivia and is used widely as a pet. Kerodon, another genus of caviid, is also used as a pet and for food. Microcavia has negatively affected humans, as it is known to ruin crops, and its burrow entrances are a danger to horses.

References and literature cited:

Feldhamer, G. A., L. C. Drickamer, S. H. Vessey, and J. F. Merritt. 1999. Mammalogy. Adaptation, Diversity, and Ecology. WCB McGraw-Hill, Boston. xii+563pp.

Lawlor, Timothy. 1979. Handbook to the orders and families of living mammals. Mad River Press, Eureka, California.

Macdonald, David. 1984. The encyclopedia of mammals. Facts on File Publications, New York.

Nowak, Ronald M. and John L. Paradiso. 1983. Walker's mammals of the world. The Johns Hopkins University Press, Baltimore and London, pp 803-810.

Vaughan, T. A. 1986. Mammalogy. Third Edition. Saunders College Publishing, Fort Worth. vii+576 pp.

Vaughan, T. A., J. M. Ryan, N. J. Czaplewski. 2000. Mammalogy. Fourth Edition. Saunders College Publishing, Philadelphia. vii+565pp.

Wilson, Don E. and DeeAnn M. Reeder (eds.). 1993. Mammal species of the world: A taxonomic and geographic reference, 2nd ed.. Smithsonian Institution Press, Washington and London.

Woods, C. A. 1984. Hystricognath rodents. Pp. 389-446 in Anderson, Sydney and J. Know Jones, Jr. (eds.). Orders and familes of mammals of the world. John Wiley and Sons, New York.

Contributors

Toni Gorog (author), Phil Myers (author), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

motile

having the capacity to move from one place to another.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate