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Saturday, November 26, 2011
Hyenas
Hyenas are the animals of the family Hyaenidae of suborder feliforms of the Carnivora. It is the fourth smallest biological family in the Carnivora (consisting of four species), and one of the smallest in the mammalia. Despite their low diversity, hyenas are unique and vital components to most African and some Asian ecosystems.
Although phylogenetically close to felines and viverrids, hyenas are behaviourally and morphologically similar to canines in several aspects (see Convergent evolution); both hyenas and canines are non-arboreal, cursorial hunters that catch prey with their teeth rather than claws. Both eat food quickly and may store it, and their calloused feet with large, blunt, non-retractible nails are adapted for running and making sharp turns. However, the hyenas' grooming, scent marking, defecating habits, mating and parental behaviour are consistent with the behaviour of other feliforms. Although long reputed to be cowardly scavengers, hyenas, especially spotted hyenas, kill as much as 95% of the food they eat, and have been known to drive off leopards or lionesses from their kills. Hyenas are primarily nocturnal animals, but may venture from their lairs in the early morning hours. With the exception of the highly social spotted hyena, hyenas are generally not gregarious animals, though they may live in family groups and congregate at kills.
Hyenas first arose in Eurasia during the Miocene period from viverrid-like ancestors, and developed into two distinct branches; the lightly built dog-like hyenas and the robust bone-crushing hyenas. Although the dog-like hyenas thrived 15 million years ago (with one taxon having colonised North America), they died out after a change in climate along with the arrival of canids into Eurasia. Of the dog-like hyena lineage, only the insectivorous aardwolf survived, while the bone-crushing hyenas (whose extant members are the spotted, brown and striped hyena) became the undisputed top scavengers of Eurasia and Africa.
