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ANIMALS
This article is from:
http://en.wikipedia.org/wiki/Hyena

All text is available under the terms of the GNU Free Documentation License: http://en.wikipedia.org/wiki/Wikipedia:Text_of_the_GNU_Free_Documentation_License 

Hyena

From Wikipedia, the free encyclopedia

 

Hyenas or Hyænas are moderately large terrestrial carnivores native to Africa and the Indian Subcontinent. They are members of the family Hyaenidae.

Physiology

Although hyenas bear some physical resemblance to wild dogs, they make up a separate biological family which is most closely related to Herpestidae (the family of mongooses and meerkats). The hyena has one of the strongest jaws in the animal kingdom and an adult of the species has only the large cats of the family Felidae (Lions, Tigers, etc.) to fear. An adult hyena's bite pressure can reach 800 lb per square inch; it can crush bone.

Hyenas range in length from 1.2–1.5 meters (3.9–4.9 ft) including the tail, which is 30 cm (12 inches) in length. An adult hyena weighs between 25 and 55 kg (55–120 lb). The pelt can be light to dark-brown on brown hyenas, while the color can be grey, sometimes nearly white on striped hyenas. Aardwolves have a warm, sand-colored coat, while the coats of spotted hyenas can range from dark-brown fur to amber and reddish in color. However, some Hyenas have spots.

Their front legs are longer than their back legs, giving them their distinctive gait. This feature, along with the fact that they have a heart twice the size of an adult lion's, allows them to stalk their prey for many miles at about 6 mph, waiting for their prey to become exhausted from the chase, and then they can move in very quick at speeds of up to 30 mph.

In ancient times, large hyenas ranged over much of Europe and Asia, but they are much reduced in range and diversity today. Only four species survive: the spotted, brown, and striped hyenas (which together make up the subfamily Hyaeninae), and the aardwolf, which is the only member of the subfamily Protelinae.

Spotted Hyena, Crocuta crocuta
Enlarge
Spotted Hyena, Crocuta crocuta

Hyenas are highly intelligent predators, and some scientists claim they are of equal intelligence to certain apes.[1] 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.[2]

One unusual feature of the hyena is that females have an enlarged clitoris called a pseudo-penis. 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 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.

Hunting

The spotted hyenas are an example of how the cooperative form of hunting can be dictated by the type of prey, as well as the predator’s ability to hunt and kill the different types of prey. When hyenas hunt an animal that is bigger than themselves, they hunt in packs and take down the prey by biting and dragging it to the ground. If they are after smaller prey, they will hunt alone in a fox-like matter.

Like dogs, but unlike some other animals in the same habitat, hyenas do not kill their prey directly. Having chased their prey to exhaustion, their prey is unable to mount any further defence of itself, and is captured and eaten while still alive. Although somewhat distasteful from the human perspective, the speedy disembowelment of the prey means that death often comes sooner than with the methods employed by other predators (for example, suffocation) and is an efficient means of eating which lessens the probability of the kill being lost to another predator.

Hyenas adapt their specific hunting strategy to the environment in which they live. In the Ngorogoro Crater, there is a very rich and concentrated amount of prey, and there are relatively many great beasts such as wildebeest or zebras. These animals are very much bound to one place and don’t migrate. Here, hyenas live in large clans (between 10 and 100 members per clan) and have established hunting territory which they often defend against neighbouring clans. The amount of large prey animals makes cooperative hunting more necessary than in the Serengeti, for example, where the clans often aren’t that large 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. Hunting in packs is proven to be more effective and fast than hunting alone, especially with large prey animals.

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 has specialized in hunting zebras. For instance, the “wildebeest hunters” often hunt in small groups (often 2–7 hyenas). When they approach the wildebeest herd, one of them runs into the herd and causes confusion. Then, it picks out a certain animal (usually the oldest, youngest or one that is wounded or weak) it begins to hunt down. The other hyenas then join it, scaring all other wildebeest away and concentrating on the unfortunate chosen one. Such a hunt can go for a couple of kilometres, with a speed up to 64 km/h in short bursts. When the prey is down, the hyenas share the food according to rank and dominance usually without any major fights. In spite of the fact that they are equally hungry, they are tolerant and respect each others’ ranks. The more is usually the better, since the prey can be effectively defended against other predators, such as lions.

The hunting of zebras is slightly different, however, since the social structure of wildebeest and zebra are different. The zebras huddle together when they spot the hyenas, and run away close to each other. A group of hyenas that are after zebras will find this hunt difficult, because the leading stallion fiercely defends his herd with kicks and bites. Again, one single hyena must run up in front and distract the stallion, while another picks out an animal. As soon as this hyena bites, the others will join in, while two hyenas constantly distract the stallion, until it gives up.

An average number of 11 hyenas is often required for such a hunt, but the number doubles up when it is feeding time. There are most often 6 hyenas hunting a wildebeest, but the number on feeding time is the same as with zebras.

The difference in numbers when hunting is connected to how well the prey is able to defend itself. Hyenas only hunt the prey they are able to at the specific time (four hyenas, for example, wouldn‘t try hunting down a zebra). The size and behaviour of the hunting parties is therefore directly connected to the size and behaviour of the prey animals.

Fighting

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.

If a clan member spots an intruder, it will quickly start scent marking, to make the intruder aware of that he is not welcome. Furthermore, the clan member will raise tail and make a whooping noise to warn the rest of the clan. Typically, the intruder will slink away before any physical contact is made.

The situation is different, however, when it comes to two clans fighting each other. The rules are much the same if it is one clan intruding into hostile territory. Hyena clans may try to take over weaker clans' territories, because of lack of prey or peace in their own territory. Human interaction is among the reasons hyena clans do this, because human activities often cause hyena territories to shrink or reduce the available prey population.

When a member of the defending clan spots an enemy clan that has come too close, it calls the whole clan together. Cubs are sent down to their dens and some selected adult females stay and guard them. The other adults, male and female, huddle together with bristling manes and raised tails, making a rumbling "giggle". They form a kind of a wall, to keep the intruders from reaching further into their territory and most importantly, their cubs. The defenders stand their ground and occasionally, one defending hyena rushes out and attacks the enemies. More defenders typically follow, while there are always some hyenas holding their ground, making sure no intruders pass through. The attackers try to push themselves forward as well as possible. If the defenders try to spread them, they typically lunge over the hyena that started the attack to provoke the others and make them unsure.

Fights between clans actually are based on a strict set of rules, and while often portrayed as brutal and reckless, hyena clans will often co-ordinate their attacks. The winning clan is usually the bigger, more numerous one, but not necessarily: If a clan has few members, but those members are extremely bold, they may gain the upper hand.

The rules are slightly different when it comes to two clans on neutral territory. Then it typically is about defending or stealing a kill, but since this isn't as valuable as a territory or young cubs, battles (if there are any) are normally very short and the winner is often the group with most members.

Nevertheless, under normal circumstances, these clan confrontations are rare compared to the many confrontations clans have with lions. When defending territories and dens, the behavior is similar to when the clan is attacked by other hyenas. There is increased attention on the cubs, though, since lions often pay visits to hyena territory to kill their offspring.

Again, the hyenas huddle together to form a wall. It is naturally easier for the lions to break this wall, because of their bulk, but the hyenas quickly form it again as soon as they are spread. If the hyenas are too few, they will not attack the lions, but stay in defense, trying to tire the big cats out.

If the hyenas are numerous enough, however, they lunge forward and aim for the lions' hindquarters and try to rip their haunches and bite their tails off. Since lions have both teeth and claws to fight with, hyenas are more likely to attack from the behind and drag the lion down on the ground, where they attempt to tear the soft belly apart.

If it is the hyenas that are the attackers and are out to kill the lions' offspring, they come in large numbers, distracting most of the adult lions while a couple of quick hyenas snatch the cubs. At least four hyenas are needed to chase off a lioness, while at least six hyenas are required to even up a confrontation with an adult male lion. Again, biting and tearing from behind is preferred rather than facing the big cats' deadly claws.

Similar behavior is seen when stealing a kill, which hyenas are quite successful at. When defending a kill, the hyenas can be the losers when lions are involved, since they don't hunt in extremely large groups but rather prefer to kill several times the same night. The lions often come in large raiding parties to make sure they can steal the hyenas' prey. However, hyenas have learned to deal with this and usually they are fortunate enough to call more of the clan together and take their prey back, unless an adult male lion is present, as male lions seem to truly terrify hyenas and hyenas rarely challenge them.

Stealing kills from cheetahs and leopards and other loners, on the other hand, rarely requires fighting and calling the clan. It can get a bit dramatic when a hyena clan faces a pack of African wild dogs, but not nearly as violent as encounters with lions. Usually, it is the wild dogs that back out. In spite of being fierce killers, wild dogs are more docile than the aggressive hyenas.

Digestion

Hyenas have extremely strong jaws and compared to their body size, they are one of the most powerful of the mammals. They also have a very powerful digestive system with highly acidic fluids. This makes them capable of eating and digesting their entire prey, including skin, teeth, horns, hooves and even bones. Since they eat carcasses, their digestion system deals very well with bacteria.

Life within the clan

A group of spotted hyenas (called a "clan") can include 5–90 members and is led by a single alpha female called the matriarch. A complicated social hierarchy governs the clan, which cubs often learn before they begin to walk. Females are the dominant members, followed in rank by cubs, while adult males rank lowest. Male hyenas, which are usually smaller and less aggressive than females, often leave the clan when they are about two years old. 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 patient 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)

Skull of Hyaena eximia
Enlarge
Skull of Hyaena eximia
Lower jaw of Hyaena eximia
Enlarge
Lower jaw of Hyaena eximia

Hyenas are born with teeth, which means that sometimes when the cubs fight they can kill each other. BBC's Carnivore! has footage showing the deadly infighting of cubs from the moment they are born. When Paula A. White studied the correlation of cub survival with maternal rank, she found that primary causes of cub death were "intraclan infanticide, disease, orphaning, predation by lions, and a mechanism of filial infanticide" . Hyenas produce milk high in nutrients, so, unlike lions and wild dogs, they can leave their cubs for about a week without feeding them. This allows them to follow the herds of wildebeest, thus ensuring that they can obtain the best prey.

Scavenger

Despite common belief, only some species belonging to this family are scavengers, and most of the prey consumed by hyenas was killed by hyenas. The brown and the striped hyena are the only true scavengers, deriving most of their food from others, and the spotted hyena is a true predator, and the most effective predator on the African Savannah.

Hyenas in popular culture

Hyenas are frequently portrayed as villains in film. This, however, is understandable: even in the early researches of these animals, naturalists knew little about them. They were mysterious, lived in groups, hunted at night and made sounds that are quite human-like (for example the "laughing"). There was much folklore about hyenas because they typically scavenge most during the day, where the humans have possibility to see it. At night, they were feared because this was their natural hunting time and they come out in great numbers. Nocturnal animals often are mysterious in folklore as well as real life. The carrion-eating made the hyena even more unpopular and it didn't make it better that the animals often dug up graves to eat the remains of corpses down there. This behavior made them seem unclean and cowardly, and because of the usual bickering between the ranks and their enormous appetite, they were thought to be greedy and selfish. In local folklore, it was believed that the sight of a hyena's shadow could strike dogs dumb with fear and the sight of its skin would even make the leopard's fur fall out in fright.

Early naturalists thought hyenas were hermaphrodites or the result of the mating of a dog with a wolf. According to early writings such as Ovid's Metamorphoses and the Physiologus, the hyena continually changed its sex and nature from male to female and back again. It, therefore, became an image of sexual deformity, prostitution, and deviant sexual behavior.

It was believed to have powers of divination and fascination and to know the secrets of magic, the dead, and various hidden or demonic forces. It was thought to imitate human voices and call its victims by name. This talent made it a symbol of the Devil who disguised his tempting voice as that of an angel. He caused confusion in his prey and hypnotized them with his shadow or the touch of his paw. It was believed that the souls of humans it had eaten remained forever visible in the eyes of the hyena who devoured them. Sorcerers hunted with hyena packs and became hyenas themselves in order to tear their enemies apart. Witches and ghosts were thought to ride upon these beasts.

In modern culture, these images still stick on to the hyenas. Hyenas, especially spotted ones, are hard to train for movies. Their wild instincts are difficult to tame and they are proven to be too intelligent for their own good and refuse to constantly do the same trick, simply because it bores them. They have, however, been used in animated movies many times. Mostly, they are portrayed as savage, unintelligent, hungry and cowardly brutes, opposing the "royal lion". The three hyenas Shenzi, Banzai and Ed play this role in the Disney movie The Lion King. They are still vicious and greedy, but extremely cowardly, only daring to attack when they are many. They are popularly used henchmen or spies by greater animals (as in Kimba the White Lion) or as cannonfodder in battle. Sometimes, they are even placed randomly in movies, only to oppose a lion character. In Disney's The Chronicles of Narnia: The Lion, the Witch and the Wardrobe, a hyena is seen snapping at Aslan the lion's feet, when he walks to the Stone Table. C.S. Lewis, author of the popular books, never mentioned a hyena, and the movie character never had a bigger role than the snapping, so this proves excellently how media still portrays the hyenas as bad guys, despite the evidence of their admirable traits.

Devilish CGI hyenas were used for Exorcist: The Beginning where they were supposed to attack a young boy.

However, their laughing can also make them excellent comic reliefs - they are not necessarily villains, but random characters (as in several episodes of the TV cartoon Cow and Chicken), idiotic and humouristic. Sometimes, the laughing is a cover and the hyena behind is a serious, intelligent or even depressed character, like the real life clowns. A very depressed sidekick, named Hardy Har Har, is shown in Hanna-Barbera's Lippy the Lion. This hyena hardly ever smiles and never actually laughs, making him a bit of an odd-ball.

Classification

Family Hyaenidae

  • Subfamily Hyaeninae
    • Spotted Hyena Crocuta crocuta (this is the "Laughing Hyena")
    • Brown Hyena Parahyaena brunnea (formerly Hyaena brunnea)
    • Striped Hyena Hyaena hyaena
  • Subfamily Protelinae
    • Aardwolf Proteles cristatus

Notes

  1. ^ Said by biologist Jeff Corwin, in an episode of "The Jeff Corwin Experience" concentrating on spotted hyenas
  2. ^ "The Book about Animal Psychology" ("Bogen om Dyrepsykologi"), chapter 4, "Social behaviour" by Danish biologist Hans Lind.


 

See also

  • Pachycrocuta

÷==External links==

Commons logo
Wikimedia Commons has media related to:
Hyaenidae
  • Hyena: Wildlife summary from the African Wildlife Foundation
  • Robin M. Weare's Hyena pages
  • Nature-Wildlife
  • Excerpt about hyenas from Richard D. Estes's "The Safari Companion" (ISBN 1-890132-44-6)
  • Kay E. Holekamp laboratory
  • Hyena photo and information
  • A mechanism for virilization of female spotted hyenas in utero
  • The Hyaenidae Family from Lioncrusher's Domain
  • The Hyaena Specialist Group
  • "Hyenas" The Movie: The First Horror Movie About Hyenas
Retrieved from "http://en.wikipedia.org/wiki/Hyena"