Aardwolf and Hyenas (Hyaenidae)

(vertebrate zoology) A family of catlike carnivores in the superfamily Feloidea including the hyenas and aardwolf.

(Hyaenidae)

Class: Mammalia

Order: Carnivora

Family: Hyaenidae

Thumbnail description
Large carnivores with powerful forequarters and less well developed hindquarters, large heads, powerful jaws and robust teeth, with medium length tails and four toes on each limb; the aardwolf is a diminutive form with poorly developed teeth and five toes on the forefeet; well developed anal pouches are present in all species

Size
Shoulder height 18–30 in (45–75 cm); head and body length 38–52 in (95–130 cm); 20–190 lb (9–85 kg)

Number of genera, species
3 genera; 4 species

Habitat
From woodland savanna to desert

Conservation status
Lower Risk/Near Threatened: 2 species; Lower Risk/Least Concern: 1 species

Distribution
Africa, except for the rainforests, and southern Asia as far as the Bay of Bengal

Evolution and systematics

Hyenas are the smallest carnivore family today, and probably arose from civets Progenetta. They were the dominant carnivores in the Middle and Upper Miocene of Eurasia. The majority of these forms were generalized, dog-like carnivores rather than the hunter-scavenger and bone-crushing species of today. However, the largest hyena to ever live, Pachycrocuta, was a 440 lb (200 kg) mega-scavenger capable of splintering the marrow bones of an elephant. The splits between the lineages leading to the extant forms are old, stretching back to the late Miocene more than nine million years ago. Palaeontological and molecular studies have shown that the aardwolf (Proteles cristatus) diverged from other hyenas some 15–32 million years ago (mya). The spotted hyena (Crocuta crocuta) split from the brown hyena (Hyaena brunnea) and striped hyena (Hyaena hyaena) 10 mya, and the brown and the striped, which are each other's closest relatives, split six mya. In the absence of clear-cut data regarding rank among hyenas and because the molecular data unite striped and brown hyenas as sister taxa relative to Crocuta and Proteles, the two are placed in the genus Hyaena. However, recognizing that the split between brown and striped is relatively old, the two have been placed in different subgenera Hyaena (Parahyaena) and Hyaena (Hyaena) respectively.

Two subspecies of the aardwolf are recognized because of its disjunct distribution, P. c. cristatus in southern Africa and P. c. septentrionalis in eastern and North Africa. On the basis of skull size, the five currently recognized striped hyena sub-species probably form two larger groups, a northeast Africa-Arabian group comprising H. h. dubbah and H. h. sultana, and a northwest African-Asian group composed of H. h. barbara, H. h. syriaca, and H. h. hyaena. No subspecies of the spotted hyena and brown hyena are recognized.

Physical characteristics

The three large species are dog-like (but they are not closely related to dogs), weighing between 57–187 lb (26–85 kg), with powerful forequarters, large necks and heads and less well developed hind quarters, giving the appearance of a sloping back. In contrast the aardwolf is diminutive, weighing about 24 lb (11 kg). The tail in all is quite short but bushy. The coat of the spotted hyena is short but in the other species it is long and shaggy with an erectile main. There are four toes on each foot, except in the forefeet of the aardwolf which have five. Front feet are far larger than hind feet giving a distinctive track. The premolars are robust and conical, except in the aardwolf where they are reduced to small pegs. The penis is boneless. In all species a large anal pouch secretes scent onto grass stalks in a unique behavior known as pasting.

Distribution

Mainly a sub-Saharan Africa family, with no species being found in the rainforests of the Congo and only the striped hyena occurring in North Africa, continuing through into southern Asia as far as India.

Habitat

Wide habitat tolerance from heavily wooded savannas to desert.

Behavior

For such a small family, the Hyaenidae show great variability in behavior and social organization, varying from the highly social, clan-living spotted hyena, the monogamous aardwolf, and the blatantly solitary but secretly social brown hyena.

Feeding ecology and diet

The spotted hyena is a hunter-scavenger and the brown and striped hyenas are predominantly scavengers. The ability of all three to break open bones and extract marrow, and also to digest bone, gives them access to a food source unavailable to other carnivores. The aardwolf is a specialized termite eater.

Reproductive biology

Non-seasonal breeders, except for the aardwolf. Litter size is from one to four, gestation around 90 days. They keep their young in breeding dens which are usually holes in the ground or sometimes caves. Mating systems vary by species (monogamous, polygamous).

Conservation status

Aardwolves are not considered endangered in the wild. The IUCN Red List 2002 classifies spotted hyenas as Lower Risk/Conservation Dependent and the brown and striped hyenas as Lower Risk/Near Threatened.

Significance to humans

Hyenas are often misunderstood and persecuted unnecessarily. Their important role in ecosystems and intricate behavior is often not appreciated. They play a significant role in witchcraft and folklore. They sometimes attack livestock and people, especially the spotted hyena.

Species accounts

Resources

Estes, Richard, D. The Behavior Guide to African Mammals. Berkeley: The University of California Press, 1991.

Kruuk, Hans. The Spotted Hyena. A Study of Predation and Social Behavior. Chicago: Chicago University Press, 1972.

Macdonald, David. The Velvet Claw. A Natural History of the Carnivores. London: BBC Books, 1992.

Mills, Gus, and Martin Harvey: African Predators. Cape Town: Struik Publishers, 2001.

Mills, M. G. L. Kalahari Hyaenas: The Comparative Bevioural Ecology of Two Species. London: Unwin Hyman, 1990.

Frank, L. G. "Social Organization of the Spotted Hyaena (Crocuta crocuta). II. Dominance and Reproduction." Animal Behaviour 35 (1986): 1510–1527.

Frank, L. G., and S. E. Glickman. "Giving Birth Through a Penile Clitoris—Parturition and Dystocia in the Spotted Hyaena (Crocuta crocuta)." Journal of Zoology, London 234 (1994): 659–665. ——. "Neonatal Siblicide in the Spotted Hyena (Crocuta crocuta)." Aggressive Behavior 17 (1991): 67–68.

Hofer, H., and M. L. East. "The Commuting System of Serengeti Spotted Hyaenas— How a Predator Copes with Migratory Prey. II. Intrusion Pressure and Commuters' Space Use." Animal Behaviour 46 (1993): 559–574.

Holekamp, K. E., and L. Smale. "Ontogeny of Dominance in Free-living Spotted Hyaenas: Juvenile Rank Relation with Other Immature Individuals." Animal Behaviour 46 (1993): 451–466.

Kruuk, H. "Feeding and Social Behaviour of the Striped Hyaena (Hyaena vulgaris Desmarest)." East African Wildlife Journal 14 (1976): 91–111.

Kruuk, H., and W. A. Sands. "The Aardwolf (Proteles cristatus Sparrman 1783) as Predator of Termites." East African Wildlife Journal 10 (1972): 211–227.

Richardson, P. R. K. "Aardwolf Mating System: Overt Cuckoldry in an Apparently Monogamous Mammal." South African Journal of Science 83 (1987): 405–410.

[Article by: Gus Mills, PhD]