Hyenas are the mammals belonging to the order Carnivora and the family Hyaenidae. Hyenas are the native to Asia and Africa and are represented by four living species. These species are Striped hyena, Spotted hyena, Brown hyena and the Aardwolf. It is believed that they evolved 26 million years ago and bear resemblance with the Banded Palm Civet. The civets appeared in Eurasia about 20-22 million years ago. The detailed study of the middle ear and dental structure suggest that civets are modified hyenas. It is believed that dog-like hyenas appeared 15 million years ago on the planet earth. The earlier hyenas were not bone-crushers like the modern ones but were somewhat wolf-like. The dog-like hyenas had canid-like premolars which helped them to feed on both animals and plant material. The family Hyaenidae reached its peak during the Pleistocene and was represented by 4 genera and 9 species. The bone-crusher hyenas became the dominant Old world scavengers which started feeding on the leftover meat of the sabre-toothed cats. Although they bear resemblance with the canids but they are characteristically very distinct from them. They have distinct bear-like gait, with front legs somewhat longer than the back legs. The Aardwolf, Striped hyena and the Brown Hyena have striped pelts and manes lining surrounding their necks and these lines become erect when they become frightened. The Spotted hyenas have shorter fur and bear spots instead of stripes.
The Spotted hyenas, Brown hyenas and the Striped hyenas have powerful carnassials teeth for cutting flesh and premolars for crushing the bone. The bite of the Spotted hyena is strongest. The Aardwolf has smallest teeth in comparison to the other three species and the teeth may be sometimes absent in the adult. The dentition although follows the same plan like that of the other species in the Aardwolf. The mandibles are very strong and bear powerful canines for tearing flesh. Like the felids hyenas lack molars. The premolars do not interfere with the functioning of the carnassials teeth. Spotted hyenas live in very complex societies which are similar to that of the primates and bear individuals of different size and structure. The cooperation and competition has also been observed in such societies. They are very intelligent animals that can be identified from their hunting methods as well as by their defense strategies.
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Sexual dimorphism is well developed in majority of the species with males slightly larger than the females. The Spotted hyenas are exception to this rule as in them the females are larger than the males. The Spotted hyenas have one unusual feature. The females are provided with a larger clitoris which is also known as pseudo-penis or demi-penis. The female hyenas, urinate, copulate and give birth to the young ones through their extended genitalia. The genitalia stretch at the time of copulation allowing the penis of male to enter and it also stretches at the time of birth of the offspring. The genitalia are strictly under the control of the female. The activity of the genitalia is under the control of androgens. The male also participates in cub rearing but the female dominates him. All the species are known to excrete an oily and yellowish substance from their anal glands in order to mark their territories. When scent marking is performed the anal pouch is everted out of the body. The anal glands are also sniffed at the time of greeting with other members of a group. Hyenas are also known to carry strains of rabies but do not develop any symptom at all.
Three out of the four species are distributed in the sub-Saharan Africa where they are found in the savannah, bush land and the desert. The fourth species or the Striped Hyena id found in the northern and eastern Africa as well as in Asia from Middle East to India. Except the Aardwolf all the species are hunters and scavengers. Aardwolf feeds on termites so lacks other similar features like that of its cousins. They do not regurgitate and food is readily digested. They have very powerful jaws in comparison to their body size and tough digestive system with highly acidic fluids which enables them to digest the skin, bone, teeth and horns. Hairs and hooves are usually regurgitated. Spotted hyenas are predators preying on the ungulates.
Hyenas are associated with gluttony, cowardice and uncleanliness. They are also a part of many cartoon movies like the Disney movie The Lion King.
Hyenas: Symbols of Cowardice
Navodita Maurice
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