Aardwolf and hyenas

(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

List of Species

Spotted hyena

Crocuta crocuta

taxonomy

Crocuta crocuta (Erxleben, 1777), Guinea, Ethiopia, Cape of Good Hope, designated as Senegambia by Cabrear (1911). No subspecies recognized.

other common names

French: Hyène tachetèe; German: Fleckenhyäne.

physical characteristics

The spotted hyena is the largest member of the family. The body color is off-white to brown with dark irregular spots, although some older individuals, particularly females, may lose their spots. The ears are rounded. The tail is black. An adult stands about 34 in (85 cm) at the shoulder. The female is larger than the male; in southern Africa females weigh up to 190 lb (85 kg) and males about 135 lb (60 kg). Southern African spotted hyenas are larger than those in East Africa where the females weigh only about 125 lb (55 kg) and the males 110 lb (49 kg). The female also mimics the male's reproductive organs; she has a pseudo scrotum and the clitoris has become large and penis like. This bizarre organ also contains the opening of the urogenital canal so that a female gives birth through it.

distribution

Mainly confined to the larger protected areas of Africa south of the Sahara, reaching its highest densities in East and southern Africa in parks where large to medium sized prey are abundant.

In West Africa its distribution is particularly patchy and it is extinct in southern South Africa.

habitat

The spotted hyena has a wide habitat tolerance and until recently was found throughout sub-Saharan Africa except for the tropical rainforests, the top of alpine mountains and extreme desert areas.

behavior

Spotted hyenas live in female dominated groups called clans that defend group territories. Females are recruited into their birth clan where they are arranged in a linear hierarchy in which daughters inherit their mother's status. Most males are immigrants, also arranged in a hierarchy, but all are ranked lower than the females. Immigrant males slowly work their way up the social ladder, spending much time developing amicable relations with the adult females so that they can mate with them.

Members of a clan partake in an elaborate meeting ceremony. They stand head to tail, lift the inside hind leg and mutually sniff at each other's erect, male-like, reproductive organs. In essence they are exposing their most vulnerable parts to each other's lethal teeth. This helps to reinforce the close bonds that exist between members of a clan that often cooperate in dangerous activities such as attacking dangerous prey, defending the territory, and mobbing their major competitors—lions.

Clan sizes and the size of their territories vary markedly depending on the amount of food available. In the arid, preypoor Kalahari in southern Africa five to ten adult spotted hyenas may inhabit a territory of over 400 mi² (1,000 km²). In the productive Ngorongoro Crater, Tanzania clans of up to 80 individuals live in territories as small as 16 mi² (40 km²). Territory clashes are common and fierce and fatal territorial battles take place. In the Serengeti, with its migratory wildebeest and zebra populations, large clans defend small territories, but individuals move through other clan's territories when they commute to the migratory herds far away from their own territory. Non-residents are submissive to and keep away from residents.

All species of hyena mark their territory by scent marking through defecating at latrines and pasting. The spotted hyena has a complex vocal system. Fourteen distinct vocalizations have been identified of which the whoop call is the most often heard and one of the characteristic sounds of the African night. They can recognize each others' whoops which are often used as a rallying call to gather scattered clan members together to help defend the territory, form a hunting party, or attack competitors. Dominant immigrant males whoop often and elaborately as a way of imprinting their presence in the territory. The famous giggle or laugh is a sign of submission, often made when several hyenas are feeding on a carcass.

feeding ecology and diet

The spotted hyena is the most successful of the large carnivores in Africa as it is equally adept as a hunter and a scavenger. It is an opportunist and has been recorded to eat almost any mammal, bird, fish or reptile, as well as man-associated organic matter. When scavenging from lion kills spotted hyenas do not always patiently wait for the larger predators to finish. If the relative numbers are right, three to four hyenas per lion and no large males, the hyenas may cooperate to force the lions off their carcass.

As a hunter it is fast, possesses great stamina and is strong enough to bring down prey as formidable as zebra and even on occasions adult buffalo and the young of rhinoceros, although their usual targets are the young of large antelope. From time to time people sleeping outside in the bush have been attacked by spotted hyenas. They are cursorial hunters that do not stalk their prey. They often run at moderate speeds through herds searching for potential victims. Once one has been selected they chase it at speeds of up to 35 mph (60 kph) for up to 1.9 mi (3 km), until either the prey outruns the hyenas, or more frequently, until the hyenas catch the prey.

Typically the spotted hyena hunts singly or in small groups of two to five. The size of the hyena hunting group depends on the prey being hunted. Largest groups hunt eland and zebra where the average is 11. On the other hand wildebeest are usually hunted in groups of three. In the case of gemsbok calves Kalahari hyenas are just as successful when hunting them singly as they are in hunting them in a group of six. Of 55 encounters seen between spotted hyenas and gemsbok herds with calves 40 (73%) were successful, a hunting success rate surpassed by few other carnivores hunting similar prey.

reproductive biology

Polygynous. Females give birth to one or two cubs, very occasionally three. The cubs are born with their eyes open and canine teeth fully erupted. Within minutes of being born they often indulge in a protracted and serious fight that establishes which of the two will be dominant and may even lead to the death of the weaker cub. This is particularly so if both cubs are female. The dominant cub is able to largely control access to the mother's milk and a cub that manages to kill its sibling will grow more quickly than if it was a twin and also have a better chance of surviving to independence at two years.

The focus of activity in a spotted hyena clan is the communal den. The females in a clan keep their cubs together, but do not suckle each other's cubs. For about the first nine months of their lives the cubs stay at the den and their major source of food is their mother's milk. They are only weaned at 14-18 months. In order to provide the nutrition needed to promote cub growth spotted hyena females produce the richest milk of any terrestrial carnivore. Their dominance ensures that they have priority at carcasses so that they can quickly eat, convert the meat into milk and get back to the den to feed the cubs. Dominant females have higher reproductive success than subordinates. They give birth to cubs at shorter intervals and have a better chance of successfully rearing young.

conservation status

Lower Risk/Near Threatened.

significance to humans

Occasionally known to attack humans and livestock.

Striped hyena

Hyaena hyaena

taxonomy

Hyaena hyaena (Linnaeus, 1758), Benna Mountains, Laristan, southern Persia. Five subspecies recognized.

other common names

French: Hyène rayèe; German: Streifenhyäne.

physical characteristics

The striped hyena has a series of black vertical stripes on a beige to pale grey body, horizontal leg stripes and pointed ears, and a mane along the back which can be held erect. The black throat patch, larger size and more massive head distinguish it from the aardwolf. The size varies from about 60 to 90 lb (26–40 kg) in different parts of its range and it stands about 28 in (70 cm) at the shoulder.

distribution

Patchily distributed in the Sahel region of north Africa as far south as Tanzania in the east, the Arabian Peninsula, the Middle East up to the Mediterranean, across southern Asia into Afghanistan and all of India. Ethiopia, Kenya and Tanzania probably hold the largest continuous population.

habitat

Mainly an inhabitant of more arid areas, even found in deserts.

behavior

Solitary when looking for food, but little is known about its behavior and social organization. It is probably similar to the brown hyena.

feeding ecology and diet

Predominantly a scavenger of vertebrate remains, supplementing the diet on reptiles, insects and birds eggs, as well as the occasional small animal which is killed. In the Serengeti the fruits of Balinites trees are highly favored and in Egypt it has been recorded to occasionally cause damage in melon fields and date plantations. In northern Kenya it is very much dependent on the lifestyle of the local Turkana herdsmen, scavenging around their homesteads, and reportedly killing their goats and sheep, although the extent to which they do so has not been properly established.

reproductive biology

Two to five cubs are born at any time of the year. In Asia often uses caves as dens, some of which have been used for many years. Mating system is not known.

conservation status

Lower Risk/Near Threatened.

significance to humans

None known.

Brown hyena

Hyaena brunnea

taxonomy

Hyaena brunnea Thunberg, 1820, Cape of Good Hope, South Africa. No subspecies recognized.

other common names

French: Hyène brune; German: Braune Hyäne.

physical characteristics

Of similar size and shape to the striped hyena, but with a dark brown to black coat except around the neck and shoulders which are white. The ears are pointed. The lower parts of the legs have white stripes. Adults weigh about 90 lb (40 kg) with little variation between the sexes. Exceptionally large brown hyenas of around 160 lb (70 kg) have been recorded from areas as wide apart as the Eastern Cape and Mpumalanga Lowveld in South Africa.

distribution

Endemic to the south west arid and drier savanna regions of southern Africa. Although its range has shrunk this century, particularly in the southern part of its range, it is still widespread and is able to survive close to human habitation.

habitat

Like the striped hyena mainly an inhabitant of more arid areas, even found in deserts.

behavior

Most sightings are of solitary individuals. A territory, which in the Kalahari is in the region of 120 mi² (300 km²) may consist of a female and her latest litter of cubs, but when food is abundant up to 14 animals will share and defend the territory, although they still forage on their own. Most clan members are relatives, although immigrant males sometimes join a clan.

Communication through visual and vocal means is limited. The most striking display is the raising of the mane along the neck and back which occurs in conflict situations. Territorial fights are usually ritualized neck-biting bouts between two animals of the same sex accompanied by loud yelling and growling by the submissive animal. The brown hyena has no long distance call.

Chemical communication is well developed. Latrines and pastings are distributed throughout the territory. Two distinct substances are pasted, a thin layer of black paste that loses its odor within hours and below that a long-acting white blob. Experiments and chemical analyses have shown that each individual leaves its own smell and that other brown hyenas can identify this. Besides territorial marking, the long-acting paste reinforces an individual's presence in the clan. The short-acting one may inform other clan members where the hyena has been foraging and help to space the hyenas evenly through the territory to lessen the chances of them competing for food.

feeding ecology and diet

With the striped hyena the ultimate mammalian scavengers, carrion from a wide range of vertebrate remains forming the bulk of the diet. These are supplemented with wild fruits, insects, bird's eggs (particularly ostrich) and kills. In the southern Kalahari killed prey makes up less than 5% of the brown hyena's diet. Of 128 hunts observed only six were successful. The prey consists of small animals like springhare, springbok lamb, bat-eared fox and korhaan (small bustards). Along the Namib Desert coast it feeds predominantly off Cape fur seal pups, but only about 3% are killed. Here it also scavenges other marine organisms washed up on the shore. Kalahari brown hyenas move an average of 19 mi (31 km) each night and sometimes over 35 mi (50 km).

reproductive biology

Brown hyena males have two types of mating systems. In one, mating is done by nomadic males that move around looking for females in heat, mate with them and then move on without investing further in their offspring. The other option is to emigrate to a clan, mate with the females in the clan and then take on parental duties by helping to feed the cubs. The latter strategy seems to be adopted in clans with more than one breeding female. For the first three months of their lives the mother visits the one to four cubs at sunrise and sunset to nurse them. As they grow the milk diet is supplemented by meat carried back to the den by the mother and other clan members. From the age of nine months the cubs begin to go on individual foraging sorties from the den that gradually increase as they become more adept at finding food and the contribution of the adults diminishes. At about 15 months they leave the den.

conservation status

Lower Risk/Near Threatened.

significance to humans

None known.

Aardwolf

Proteles cristatus

taxonomy

Proteles cristatus (Sparrman, 1783), near Little Fish River, Somerset East, eastern Cape Province, South Africa. Two subspecies recognized.

other common names

French: Protèle; German: Erdwolf.

physical characteristics

Resembles the striped hyena, but is smaller and lacks the robust neck and jaws and large teeth. It has a mane along the back that can be held erect. Its general body color is yellowish-white to rufous with several vertical black stripes along the body and one or two diagonal stripes across the fore- and hindquarters. There are also several stripes on the legs. Males and females weigh about the same, 20 lb (9 kg) in southern Africa, up to 30 lb (14 kg) in East Africa, and they stand about 19 in (47 cm) at the shoulder.

distribution

Occurs in two distinct populations. The southern population occurs over most of southern Africa as far as southern Angola, southern Zambia and southwestern Mozambique. This population is separated by a 930 mi (1,500 km) strip of moist woodland from the northern population in East Africa which ranges as far north as the extreme southeast of Egypt.

habitat

Prefers open grassy plains in the 4–24 in (100–600 mm) annual rainfall range.

behavior

The aardwolf is monogamous and territorial—a mated pair and its latest offspring occupy a territory of 0.4–1.6 sq mi (1–4 sq km), depending on the density of termites. Territories are marked by pasting. If an intruder is encountered the resident raises the long mane along its back and, particularly if it is of the same sex, it is chased to the border. Intruders usually escape and fights are rare, except between males in the mating season. Although the cheek teeth are reduced to a few small pegs, the canine teeth are well developed and they can inflict injuries to other aardwolves. Fatal fights have been recorded. Deep roars, most uncharacteristic for this delicate looking creature accompany these fights.

feeding ecology and diet

The aardwolf feeds almost exclusively on one genus of snouted harvester termite, of the genus Trinervitermes. It licks the termites off the ground while they forage at night. Normally a foraging column comprises mainly workers, however, once disturbed the proportion of workers to soldiers changes rapidly, so that the predator starts taking in more and more soldiers, which squirt noxious terpenes when attacked. Eventually the quantity of terpenes taken in becomes too much and the aardwolf terminates the feeding bout.

During the cold winters in South Africa Trinervitermes is inactive. At this time the aardwolf switches its diet and activity to feeding in the afternoon on the diurnal, pigmented harvester termite, Hodotermes mossambicus. In tropical areas of East Africa the aardwolf has a more varied diet during the rainy season when a number of other termites are also eaten.

reproductive biology

Monogamous. The aardwolf is a seasonal breeder. In southern Africa mating takes place in early July. Litter size is one to four. Cubs emerge from the den at about four weeks, begin foraging for termites around the den at nine weeks, and are weaned at four months when the denning period ends and the cubs become independent.

The male aardwolf helps to raise the young by guarding the den against predators. However, males are promiscuous. At the start of the mating season males make scouting trips into neighboring territories, when dominant males frequently mate with the females of less dominant males. The females mate with both males, thereby keeping the cuckolded male interested in the cubs.

conservation status

Lower Risk/Least Concern.

significance to humans

None known.

Resources

Books

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.

Periodicals

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.

Gus Mills, PhD