Subfamily: Hyaenidae (includes Brown, Spotted & Striped)
Subfamily: Protelinae (Aardwolf)
The suborder, Feliformia, includes hyenas, and also the true cats, mongooses, civets, and related taxa. Shared characteristics of this suborder include the possession of four carnassial teeth in the front of the jaw, and the formation of the auditory bullae (bony capsules in the middle and inner ear). The name Feliformia means 'cat-like' carnivores.
The name of the Hyena itself comes from the Greek hyaina, meaning 'swine,' though of course they are not part of that family and are not closely related in anyway. Some think this comes from the bristly mane of the hyena, which may resemble to some the bristly mane of a wild hog.
If you look at them, you probably think hyenas look a lot like dogs and maybe a bit like cats. They're actually most closely related to the viverridae family (civets, mongooses, and genets) than to either dogs or cats however. One similarity they share with civets are highly developed anal glands that they use for marking territory and for olfactory communication. Of the four types of hyena, the aardwolf is the closest to the civet because the aardwolf eats only insects.
The hyena is a medium-sized animal, with males and females being generally about the same size, excepting the spotted hyena. They have very powerful jaw muscles, excepting the aardworlf, and it has been said that the hyena has the most powerful bite of all mammals. They have 32-34 teeth, and their jaws are so powerful that they can crack bone (including the leg bone of a rhinoceros!). They have large ears that can be round or pointed. Hyena genitalia have no baculum (which is a bone commonly found in the penis of carnivores), but they do have small, backwards facing spines at the base of the penis, similar to cats.
Diet and hunting
Hyenas are carnivores and scavengers. They eat meat and carrion. A hyena's digestive system is very large and efficient - they can utilize all parts of a carcass for energy, including digesting bone and teeth in a couple of hours. Aardwolves are insectivores.
Though it used to be thought that only the spotted hyena lives in social groups, scientists have since discovered that all hyenas are social animals to one degree or another.
All four species of hyenas maintain latrines where they deposit feces, latrines that are as far as possible from the area of their dens.
All hyenas participate in olfactory communication, marking their territory by pasting an oily, yellow substance onto bushes and grass. They excrete this substance from glands in their anus. Hyenas also sniff the genitals and anus during a greeting ceremony, which can last up to 10 minutes. They also mark by scraping the ground with their paws, releasing scent from glands on their feet.
Hyenas have a range of vocalizations including whining, giggling, growling, and grumbling. Most hyenas only vocalize with members of their family. A long-distance cackle is rare. The famous hyena sounds are peculiar to the spotted hyena. These are the whooping call they use for warning and the 'laugh' that indicates fright.
Hyenas also use visual communication to indicate mood or rank within the society. These can demonstrate dominance or submission to another hyena. A dominant hyena will bristle, erect her tail and ears, hunch her back and growl. A submissive hyena will present his anal glands, flatten his ears, lick his lips, and grimace.
When fighting, hyenas bite each other in the neck or rump areas, wrestle muzzles by gripping the other's lower jaw, and often drop their hindquarters to the ground to protect their back legs.
Hyenas arose in the Miocene, about 10 million years ago or so, from ancient relatives of the civet in Eurasia. Their success can be directly related to their efficient digestive system - other carnivores of the era could not make use of all parts of the carcass (such as bone) like the hyena.
In ancient times there were more species of hyenas than exist today. The peak of diversity was during the Pleistocene, with 4 genera and 9 species of hyena. 69 different species have been found in the fossil record, of which many have not been named.
The earliest known member of the hyaenidae is Protictitherium Gaillardi, which looked a lot like a civet, had retractable claws, and lived in trees. Several other species of Protictitherium lived during the Miocene after Gallardi. The first known European hyaenid was Plioviverrops Orbignyi, which specialized in insects.
Other hyaenids began evolving after this, getting bigger and changing dentition. Some became running hyenas, some small predators like jackals, and some started down the road to the bone-crushing hyenas of today.
The best known of the jackal-like hyenas was Ictitherium Viverrinum, which lived between 11 million and 6 million years ago. The genera of running hyenas were Chasmaporthetes, Lycyaena, and Hyaenictis. Chasmaporthetes crossed the Bering land bridge to America where it evolved into Chasmaporthetes Ossifragus, becoming North America's only native hyaenid before being brought to extinction by the end of the Ice Age.
The bone-crushing hyaenids included the genera of Belbus, Palinhyaena, Ikelohyaena, and Leecyaena. The teeth on these species got larger and heavier, but little is known about them beyond that because all we have discovered are fragmentary skulls. The most extreme bone-crusher was Adcrocuta Eximia, which lived in Greece, which had an even more powerful jaw than today's spotted hyena.
At the end of the Miocene, these early hyaenids became extinct. The Chasmaporthetes survived longer than most, as did a giant version of the spotted hyena that we call the cave hyena. Two other species evolved, Tongxinictes and Tungurictis, but they didn't last long. Hyaenids became extinct in Europe, only remaining in Africa in the 4 species we know today.
The aardwolf is currently believed to have split off early from the rest of the hyaenid family, but there is nothing that has been discovered that relates to the aardwolf in the fossil record, so he remains a mystery.