- Spotted Hyena
Also known as the laughing hyena,the spotted hyena has a strong and well developed neck and forequarters, but relatively underdeveloped hindquarters. The rump is rounded rather than angular, which prevents attackers coming from behind from getting a firm grip on it.The head is wide and flat with a blunt muzzle and broad rhinarium. In contrast to the striped hyena, the ears of the spotted hyena are rounded rather than pointed. Each foot has four digits, which are webbed and armed with short, stout and blunt claws.
The paw-pads are broad and very flat, with the whole undersurface of the foot around them being naked. The tail is relatively short, being 300–350 mm (12–14 in) long, and resembles a pompom in appearance. Unusually among hyaenids, and mammals in general, the female spotted hyena is considerably larger than the male. Both sexes have a pair of anal glands which open into the rectum just inside the anal opening. These glands produce a white, creamy secretion which is pasted onto grass stalks by everting the rectum. The odour of this secretion is very strong, smelling of boiling cheap soap or burning, and can be detected by humans several metres downwind.
The spotted hyena has a proportionately large heart, constituting close to 1% of its body weight, thus giving it great endurance in long chases. In contrast, a lion's heart makes up only 0.45–0.57 percent of its body weight. The now extinct Eurasian populations were distinguished from the modern African populations by their shorter distal extremities and longer humerus and femur.
The skull of the spotted hyena differs from that of the striped hyena by its much greater size and narrower sagittal crest. For its size, the spotted hyena has one of the most powerfully built skulls among the Carnivora. The dentition is more dual purposed than that of other modern hyena species, which are mostly scavengers; the upper and lower third premolars are conical bone-crushers, with a third bone-holding cone jutting from the lower fourth premolar.
The spotted hyena also has its carnassials situated behind its bone-crushing premolars, the position of which allows it to crush bone with its premolars without blunting the carnassials. Combined with large jaw muscles and a special vaulting to protect the skull against large forces, these characteristics give the spotted hyena a powerful bite which can exert a pressure of 80 kgf/cm2 (1140 lbf/in²), which is 40% more force than a leopard can generate. The jaws of the spotted hyena outmatch those of the brown bear in bonecrushing ability, and free ranging hyenas have been observed to crack open the long bones of giraffes measuring 7 cm in diameter. A 63.1 kg (139 lb) spotted hyena is estimated to have a bite force of 565.7 newtons at the canine tip and 985.5 newtons at the carnassial eocone.
Spotted hyenas are social animals which live in large communities (referred to as "clans") which can consist of at most 80 individuals. Group-size varies geographically; in the Serengeti, where prey is migratory, clans are smaller than those in the Ngorongoro Crater, where prey is sedentary. Spotted hyena clans are more compact and unified than wolf packs, but are not as closely knit as those of African wild dogs. Females dominate males, with even the lowest ranking females being dominant over the highest ranking males.
It is typical for females to remain with their natal clan, thus large clans usually contain several matrilines, whereas males typically disperse from their natal clan at the age of 2½ years. The clan is a fission-fusion society, in which clan-members do not often remain together, but may forage alone or in small groups. High-ranking hyenas maintain their position through aggression directed against lower-ranking clan-members. Spotted hyena hierarchy is nepotistic; the offspring of dominant females automatically outrank adult females subordinate to their mother.
However, rank in spotted hyena cubs is greatly dependent on the presence of the mother; low-ranking adults may act aggressively toward higher-ranking cubs when the mother is absent. Although individual spotted hyenas only care for their own young, and males take no part in raising their young, cubs are able to identify relatives as distantly related as great-aunts. Also, males associate more closely with their own daughters rather than unrelated cubs, and the latter favour their fathers by acting less aggressively toward them.
Spotted hyena societies are more complex than those of other carnivorous mammals, and are remarkably similar to those of cercopithecine primates in respect to group size, structure, competition and cooperation. Like cercopithecine primates, spotted hyenas use multiple sensory modalities, recognise individual conspecifics, are conscious that some clan-mates may be more reliable than others, recognise third-party kin and rank relationships among clan-mates, and adaptively use this knowledge during social decision making. Also, like cercopithecine primates, dominance ranks in hyena societies are not correlated with size or aggression, but with ally networks. In this latter trait, the spotted hyena further show parallels with primates by acquiring rank through coalition. However, rank reversals and overthrows in spotted hyena clans are very rare.
The social network dynamics of spotted hyenas are determined by multiple factors. Environmental factors include rainfall and prey abundance; individual factors include preference to bond with females and with kin; and topological effects include the tendency to close triads in the network. Female hyenas are more flexible than males in their social bonding preferences. The higher ranking adult spotted hyenas tend to have higher telomere length, thus are healthier, naturally live longer, and reproduce more.
Territory size is highly variable, ranging from less than 40 km2 in the Ngorongoro Crater to over 1,000 km2 in the Kalahari. Home ranges are defended through vocal displays, scent marking and boundary patrols. Clans mark their territories by either pasting or pawing in special latrines located on clan range boundaries. Clan boundaries are usually respected; hyenas chasing prey have been observed to stop dead in their tracks once their prey crosses into another clan's range.
Hyenas will however ignore clan boundaries in times of food shortage. Males are more likely to enter another clan's territory than females are, as they are less attached to their natal group and will leave it when in search of a mate. Hyenas travelling in another clan's home range typically exhibit bodily postures associated with fear, particularly when meeting other hyenas. An intruder can be accepted into another clan after a long period of time if it persists in wandering into the clan's territory, dens or kills.