|Hyena - Hyenas|
Are moderately large terrestrial carnivores native to Africa, Arabia, Asia and the Indian subcontinent. They are members of the family Hyaenidae.
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, 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 inverted. 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 den 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.
Birth is very difficult: the internal birth canal extends almost to the subcaudal location of the vulva (which in Crocuta is fused to form a scrotum containing fatty pseudo-testes) before turning abruptly towards the clitoris, and the clitoris itself is narrow (although it ruptures with the first parturition, making subsequent births easier). In captivity, many cubs of primiparous mothers are stillborn because of the long labor times involved, and in the wild, it is estimated that 10% of first time mothers die during labor. These factors suggests that at some point there must have been powerful selective pressures driving the evolution of masculinisation.
Researchers originally thought that one of the things that causes this characteristic of the genitals is androgens that are expressed to the fetus very early on in its development. However, it was discovered that when the androgens are held back from the fetus, the development of the female genitalia was not altered. Other hyena species lack this adaptation, making it a fairly recent one in the hyena line. Masculinised female genitalia also appears in some lemurs, spider monkeys, and the Binturong but the fused vulva is unique to the hyena.
Hyenas are born with their eyes open and teeth already fully developed after a 4 month gestation period. At birth, the cubs weigh 2.2 to 3.6 lb (1-1.6 kg), and are among the few mammals to commit neonatal siblicide. A same sexed litter will result in vicious fighting between the cubs, often resulting in death. This siblicide is estimated to contribute to 25% of hyena cub mortality. Since a single cub will receive more food and mature faster, this behavior is probably adaptive. Spotted hyena milk is very rich, having the highest protein content (14.9%) of any terrestrial carnivore, and the fat content (14.1%) is second only to the polar bear, so unlike lions and wild dogs, they can leave their cubs for about a week without feeding them. Two to six weeks after whelping, young are transported to the communal den. Young depend entirely on milk for about 8 months and are not weaned until 12 to 16 months old. Maturation is at three years, females later than males. Female offspring remain in their natal clan while males leave at around two years.
The spotted hyena is among the most vocal African mammals, with over 11 different sounds being recorded.
Subordinate members of the clan lick the pseudo-penis of a higher ranked female as a sign of submission. The matriarch's pseudo-penis is licked by all members of the clan, while male's penises are rarely licked because the highest ranked male is subordinate to the lowest ranked female.
Females tend to mate with males from other clans, thereby preventing inbreeding. Female hyenas very rarely mate with highly aggressive males. Instead, calmer and more docile males are selected. Patience is especially important since courtship can last as long as a year. For this reason, dominant and impatient males have difficulty finding mates. Despite the complicated courtship, the female raises her pups without the male. Infanticide is common. "Prior to the mother's return, another adult female (a full sister to the new mother) arrived and methodically killed both newborns with crushing bites to the head" (Paula A. White)
Hyenas within the same clan rarely fight in a way that can damage them seriously. Most bickering is settled quickly, even by members that have similar ranking in the social hierarchy. Some loud noises and a couple of light bites is usually enough, and if the fight ever gets out of hand, it is quite normal for a hyena of a higher rank to step in and interrupt the fight.
Even hyenas that are strange to each other would rather avoid battle than recklessly try to kill each other. Usually, scent marking territories avoids conflicts: if a lone hyena should enter a hostile territory anyway, it keeps a low profile and stays out in the borders. Female hyenas are treated with more hostility than males, since males from different clans are needed for breeding in the clan. Strangers are rarely accepted in a clan, but if so, they are usually placed at the bottom of the ranking system. When large scale confrontations do occur (with lions or other hyena clans), hyena form a distinctive "wall" by standing shoulder to shoulder and advancing on the threat as a group.
Like many social carnivores, spotted hyenas are playful, especially when young. In captivity they can become very tame, and both native Africans and Europeans living in Africa have sometimes successfully made pets of them.
The spotted hyena is primarily a solitary hunter, making 75% of its kills alone. Kills made in this way are the most prevalent but the success rate (26%) is much smaller than the success rate of hunts attempted by small groups consisting of 2-4 hyenas (46%). When hunting in small groups, the hyenas approach their prey from downwind (so their scent is not picked up by the prey) in fan formation to promote an uneven dispersal of the target prey. When the prey are dispersed in this way, it is easier for the group to spot lame individuals and to separate the young from older individuals.
Spotted hyenas hunt in a manner similar to African wild dogs, chasing their prey for long distances waiting for it to exhaust itself. Having chased the prey animal to exhaustion, the hyenas pull it to the ground and disembowel it. Small prey is killed with a bite to the skull. A hyena can eat 33 pounds (15 kilograms) of meat per feeding.
Hyenas adapt their specific hunting strategy to the environment in which they live. In the Ngorongoro Crater, there is a very rich and concentrated amount of prey. These animals are very much bound to one place and do not migrate. Here, hyenas live in very large clans (between 10 and 100 members). The amount of large prey animals makes cooperative hunting more necessary than in the Serengeti for example, where the clans are often smaller and must follow the herds when they migrate. Hyenas following migrating prey are less territorial, and will often hunt small animals individually as well as large ones in packs.
It is also common to see that some hyena clans actually have specialized in hunting certain types of prey. One clan may have specialized in hunting wildebeest, whilst another may have specialized in hunting zebras. Wildebeest hunters often hunt in small groups (usually 2-7 hyenas), though a single hyena is capable of bringing down a bull wildebeest unaided. When they approach the wildebeest, one hyena will run into the herd and cause confusion. It will then pick out a certain animal (usually the oldest, youngest or one that is weakened) which it begins to harass. The other hyenas will then join in chasing and attacking the chosen animal. Such a hunt can go on for a couple of kilometers, with a speed up to 64 km/h in short bursts. A chase in the Kalahari lasted 24 km before the prey, an eland, was captured.
The hunting of zebras is slightly different. The zebras huddle together when they spot the hyenas, and run away huddling close to each other. A group of hyenas hunting zebras will find this pursuit difficult, because the leading stallion fiercely defends his group with kicks and bites. Again, a single hyena runs in front of the stallion and distracts it, while the rest of the pack picks out an unprotected animal. An average number of 11 hyenas is often required for such a hunt, but the number doubles up when actual feeding begins.
Other herbivores observed to be eaten by spotted hyenas include Thompson's gazelle, topi, waterbuck, eland, Cape buffalo, impala, Warthog, hartebeest, kob and bushbuck. In addition, hyenas have been known to prey on the young of giraffe, hippopotamus and rhinoceros.
Though predominantly a hunter, the spotted hyena will devour carrion if the opportunity presents itself. The actual proportion of the spotted hyenas diet consisting of already dead animals varies depending on the ecosystem and sometimes on the density of other predators in the area. Studies carried out in the Serengeti and Ngorongoro Crater showed that the Ngorongoro Spotted Hyena scavenged very little, with around 7% of their diet consisting in already dead animals. In contrast, scavenging made up 32% of the Serengeti Hyenas dietary habits.
Hyenas have a very acute sense of smell, and can detect carcasses many kilometers away. They will also follow vultures, in the hope of being lead to an easy meal.
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.
Relationship with lions
The feud between the two species does however seem to encompass more than just battles over food. In the animal kingdom, the territorial boundaries of another species are usually disregarded. Hyenas and lions are an exception to this seeing as they set boundaries against each other as they would against members of their same species. Male lions are extremely aggressive toward hyenas, and have been observed to hunt and kill hyenas without eating them. Conversely, hyenas are major predators of lion cubs. When attacking adults, hyenas go after groups of females or better yet; a single female. However healthy adult males, even single ones, are generally avoided at all costs.
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