Hyena
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[Photo] Spotted Hyena (Crocuta crocuta) and two cubs, Ngorongoro Crater, Tanzania. Date June 2005. Photo by Budgiekiller.

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Suborder: Feliformia
Family: Hyaenidae
Subfamily Hyaeninae
- Crocuta crocuta, Spotted Hyena or Laughing Hyena
- Hyaena hyaena, Striped Hyena
- Parahyaena brunnea, Brown Hyena
Subfamily Protelinae
- Proteles cristatus, Aardwolf

Hyenas or Hyænas are moderately large terrestrial carnivores native to Africa, Arabia, Asia and the Indian subcontinent. They are members of the family Hyaenidae.

Physiology
Although hyenas bear some physical resemblance to canids, they make up a separate biological family that is most closely related to Herpestidae (the family of mongooses and meerkats), though not all scientists agree. With the exception of the insectivorous Aardwolf (Proteles cristatus), hyenas have among the strongest jaws in the animal kingdom, and an adult of the species has only the big cats (e.g. lions or leopards) to fear.

All species have a distinctly bear-like gait due to their front legs being longer than their back legs. The Aardwolf, striped hyena and brown hyena have luxurious, striped pelts and manes lining the top of their necks which erect when frightened. The spotted hyena's fur is considerably shorter and is spotted rather than striped. Unlike other species, its mane is reversed forwards.

Hyenas are highly intelligent animals, and some scientists claim they are of equal intelligence to certain apes. One indication of hyena intelligence is that they will move their kills closer to each other to protect them from scavengers; another indication is their strategic hunting methods.

The majority of hyena species show little sexual dimorphism, usually with males being only slightly larger than the females. The spotted hyena is an exception to this as females are larger than the males and dominate them. One unusual feature of the spotted hyena is that females have an enlarged clitoris called a pseudo-penis, demi-penis, or sometimes mistakenly referred to as a nanophallus. Female hyenas give birth, copulate, and urinate through their protruding genitalia, which stretches to allow the male penis to enter for copulation, and it also stretches during birth. The anatomical position of the genitalia gives females total sexual control over who is allowed to mate with them. Researchers originally thought that one cause of this characteristic of the genitals was androgens that were introduced to the fetus very early on in its development. However, it was discovered that when the androgens were held back from the fetus, the development of the female genitalia was not altered.

All species excrete an oily, yellow substance from their anal glands onto objects to mark their territories. When scent marking, the anal pouch is turned inside out, or everted. Hyenas also do this as a submissive posture to more dominant hyenas. Genitals, the anal area, and the anal glands are sniffed during greeting ceremonies in which each hyena lifts its leg and allows the other to sniff its anal sacks and genitals. All four species maintain latrines far from the main denning area where dung is deposited. Scent marking is also done by scraping the ground with the paws, which deposits scent from glands on the bottoms of the feet.

Evolution
The hyaenids have no fossil record before the mid-Miocene period, about 10 million years ago, thus making them the most recent addition to the carnivora. It is believed that the family began in Africa and spread through Europe and Asia. The hyena's peak was during the Pleistocene, with 4 genera and 9 species of hyena. Extinct hyena genera included civet-like tree dwellers and speedy species developed to run down prey, along with even more powerfully developed bone crushing species similar to modern hyena. Fossil examples include the genera Protictitherium, Ictitherium, Chasmaporthetes, Adcrocuta, Pachycrocuta and Percrocuta (of which P. gigantea was the largest Hyena which ever lived). Their success was largely due to the fact that the sabre-toothed cats which they coexisted with, were unable to make full use of their prey due to the nature of their dentition. The hyena's powerful jaws and digestive systems allowed them to consume otherwise undigestible parts. As the sabre-toothed cats began to die out and be replaced by short fanged felids which were more efficient eaters, some hyenas began to hunt for themselves and began evolving into new species, the modern spotted hyena being among them.

Most lines of hyena died out towards the end of the Miocene, possibly due to competition from early canids. The running hyena Chasmaporthetes survived until the first ice ages, and the Eurasian Cave Hyena survived until the end of the last ice age, when they died out along with much of the Eurasian megafauna.

Habitat
With the exception of the Striped Hyena which has been seen in the jungles of India, all modern Hyena species generally reside in arid environments like African savannahs and deserts.

Dietary habits
With the exception of the Aardwolf, all hyena species are efficient scavengers. They have extremely strong jaws in relation to their body size and have a very powerful digestive system with highly acidic fluids, making them capable of eating and digesting their entire prey, including skin, teeth, horns, bones and even hooves. Since they eat carrion, their digestive system deals very well with bacteria.

The spotted hyena is primarily a predator, unlike its cousins. Spotted hyenas are successful pack hunters of small to large sized ungulates and are the most abundant carnivore on the African continent.

The Aardwolf is a specialised feeder of termites, thus lacking the size and physical power of its cousins.

Hyaena brunnea

The brown hyaena is a nocturnal mammal which may travel great distances (30 km) in search of food which is located predominantly by a highly developed sense of smell (Mills & Hofer 1998 b). Like the other ‘true’ hyaenas, it is predominately a scavenger; a bone crusher which is able to digest bone, horns and teeth (Hunter 2003). However it is an extremely adaptable feeder and an opportunistic hunter which enables it to survive in the harsh Kalahari desert where no other large carnivores can (Skinner & Van Aarde 1980). Moreover, brown hyaenas have a large and extremely efficient digestive system and do not need to drink surface water. They are able to conserve water by being nocturnal, and some individuals use aardvark holes during the day to escape the heat; these holes are below the water table and contain fresh water (Maude 2005).When available during the rain season, browns will frequently visit water holes to drink (Owens & Owens 1978), but the majority of their water intake comes from their food sources such as plants and fresh carcasses. In some parts of the desert Ostrich eggs provide a source of liquid, but fruits such as tsama melons, (Citrullus vulgaris) (Maude 2005) and Gemsbok cucumber (Acanthosicyos naudinianus) are the hyaena’s preeminent source of water; having a moisture content of around 90% (Mills 1982; 1973) and also containing vitamin C. The seeds of the cucumber and melon are ingested by the hyaena and are expelled in the faeces undamaged, and growth of tsama melons has been recorded at old dens and latrines. Thus brown hyaenas are thought to be important vectors for seed dispersal (Mills 1990).


In addition to supplementing its diet with fruits and fungi such as the berries from the Brandy bush (Grewia flava) and Kalahari truffles (Terfezia pfeilii) respectively (Mills 1990), brown hyaenas will also consume insects and small vertebrate prey (Mills & Mills 1978; Mills and Hofer 1998 b; Owens & Owens 1978), with studies showing insects and reptiles are more frequently consumed by hyaenas in the southern Kalahari than in the central Kalahari (Owens & Owens 1978). Brown hyaenas do hunt, but unlike the highly specialised cooperative hunting of spotted hyaenas, the browns technique is regarded as a ‘primitive chase and grab affair’(Mills 1990). In a study in the Southern Kalahari, only 4.2% of the diet consisted of hunted vertebrates, and prey species are generally small, or medium sized, typically springhare, springbok and bat-eared foxes. Such hunting is unspecialised and opportunistic, with the vast majority of hunts being unsuccessful, especially in comparison to the spotted hyaena, e.g brown hyaenas have a 6% success rate in comparison to 31% success rate of spotted hyaenas when hunting springbok lambs (Mills 1990). Brown hyaenas increase hunting attempts when carrion is less available such as in the dry season (Owens & Owens 1978), but relative to the spotted hyaena, hunting constitutes only a small fraction of the foraging budget of the brown hyaena. A study by Mills (1987) showed that hunting accounted for only 5.8% of food biomass which was comprised of small species such as springhares, whereas for spotted hyaenas, hunted prey accounted for 72.6% of food biomass, and was predominantly formed of ungulates (68%).

Brown hyaenas of the central Kalahari have been observed to stalk and to dig at borrows of springhare; there is no comment on the success rate of these actions (Owens & Owens 1978).

Along the Namib coast, brown hyaenas hunt Cape fur seal cubs (Arctocephalus pusillus), and scavenge the remains of adult seals and other marine organisms washed up on to the shore (Skinner et al 1984, Skinner et al 1995; Burgener & Gusset 2003). Even though seal cubs are in abundance, the brown hyaena shows a preference for scavenging rather than hunting (Mills 1990; Skinner et al 1995). Of those seal cubs hunted and killed, the carcasses were never seen to be completely consumed, with only the brain and intestines being devoured. Hyaenas of the Namib coast were also observed to chase after domestic dogs (Canis familiaris), flamingos (Phoenicopterus spp.) and geckos, and scavenge human refuge (Skinner et al 1995).

In agricultural areas, the diet consists of small indigenous vertebrates and livestock as carrion. Reports of brown hyaenas killing calves, lambs, sheep (Skinner 1976) goats and other small livestock have been documented (see Table 3), although is not very common and usually a single individual is responsible for the majority of kills (Mills & Hofer 1998 b). Preliminary data from a questionnaire investigating the economic damage inflicted by brown hyenas and other carnivores in non-protected areas throughout the north west province, reveals that although some farmers have reported damage to their livestock by brown hyaenas, (some of which are credible, others less so) they are perceived by the farmers as a lesser threat to livestock than jackal and caracal.

Brown hyaenas have been observed to frequently cache food items, predominantly legs both fleshy and bone, storing them in dense bush around 100-600 m from the site of the kill to which the hyaena returns the following night, or after the main carcass has been expended (Owens & Owens 1978). This behaviour is suggested to be a method of competition with other brown hyaenas; rather then eating quickly or engaging in aggressive encounters with other hyaenas, (typical of spotted hyaenas (Kruuk 1972)) an individual will compete at a carcass directly by quickly removing the legs for caching, or indirectly by competing for social status (Owens & Owens 1978).

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