Hyaenidaeaardwolf and hyenas(Also: aardwolf; hyenas)

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The family Hyaenidae contains four species, each in its own genus, found in Africa, SW Asia, and India. Three species, which include the animals we usually think of as hyaenas (Crocuta crocuta, Hyaena hyaena, and Hyaena brunnea), hunt and scavenge large vertebrate prey. The fourth species, the aardwolf (Proteles cristata), subsists almost exclusively on termites.

Hyaenas are medium to large in size, 10-80 kg. They have a bushy tail, rounded ears, and three of the four species have stripes or spots on their coats (the brown hyaena, Parahyaena, is unmarked). A mane may be present. A striking feature is the disparity in length between the front and rear limbs. This disparity, plus large head and forequarters relatively larger than hindquarters, makes them seem like they're always running uphill. Their stance is digitigrade and their claws are blunt and non-retractile. A unique feature of Crocuta is the enlarged clitoris and 2 scrotal pouches of the female, which are externally indistinguishable from the penis and scrotum of the male. This morphological characteristic led to the belief that hyaenas were hermaphroditic (definitely not true!). Another unique character is the anal pouch, which the animals evert to mark objects within their territories with odoriferous secretions. Anal pouches are also well developed in the related viverrids and herpestids. Hyaenids lack a baculum.

Hyaenas are characterized by massive jaws (except for Proteles) and large premolars and molars used to crush bone. The cheekteeth of Proteles are reduced in size, although its canines are sharp and fairly large. The incisors of hyaenids are unspecialized, except that the third incisor on each side is larger than the others. The dental formula of Proteles is 3/3, 1/1, 3/2-1, 1/1-2 = 28-32; that of other hyaenas is 3/3, 1/1, 4/3, 1/1 = 34. Their skulls lack alisphenoid canals, their auditory bullae are divided like those of other feloids (but the septum is not easily visible), and their parocciptial processes lie against their bullae, also resembling cats.

Although hyaenas are commonly thought of as scavengers, they are also skilled hunters that are able to take down quite large prey, especially when they hunt cooperatively. They seem to rely primarily on their sense of smell. In times of scarce resources, hyaenas forage individually, covering large distances in search of food. A large foraging range is beneficial in finding carrion, which is generally unpredictably located both in space and time. Another foraging trait is the ability to cue on other species, such as lions, cheetahs, and vultures, to locate possible sources of food. At a kill, a group of hyaenas can often give lions a run for their money. In a conflict between lions and hyaenas, the winner is usually the species with the most individuals.

Hyaena clans are centered around females, which are dominant to and larger than the males. Males disperse, whereas females generally stay with natal groups. Each clan usually defends a territory, which contains the foraging and denning areas. Some clans do not have fixed territories, but follow migratory ungulates such as wildebeest. Other clans are migratory for parts of the year but have fixed territories other parts of the year. Hyaenas usually den in the abandoned burrows of other animals, caves or thick brush.

Phylogenetically, the Hyaenidae are most closely related to the viverrids, herpestids, and cats. Their fossil record goes back to the Miocene.

Technical characters 1

Technical characters 2

Literature and references 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.

IUCN Hyaena Specialist Group. 2007. Hyaena Specialist Group Website, accessed at http://www.hyaenidae.org/.

Paradiso, J. L. 1975. Walker's Mammals of the World, Third Edition. Johns Hopkins University Press, Baltimore.

Savage, R. J. G. and M. R. Long. 1986. Mammal Evolution, an Illustrated Guide. Facts of File Publications, New York. 259 pp.

Stains, H. J. 1984. Carnivores. Pp. 491-521 in Anderson, S. and J. K. Jones, Jr. (eds). Orders and Families of Recent Mammals of the World. John Wiley and Sons, N.Y. xii+686 pp.

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, D. E., and D. M. Reeder. 1993. Mammal Species of the World, A Taxonomic and Geographic Reference. 2nd edition. Smithsonian Institution Press, Washington. xviii+1206 pp.

Contributors

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