Spotted Hyena

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Spotted Hyena
Conservation status
Conservation Dependent
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Mammalia Order: Carnivora Family: Hyaenidae Genus: Crocuta Species: C. crocuta
Binomial name
Crocuta crocuta (Erxleben, 1777)
Spotted Hyena range

The Spotted Hyena, or Laughing Heyena, (Crocuta crocuta) is the largest and best-known member of the family Hyaenidae. They are moderately large terrestrial carnivores native to Africa. The Greek root ("krokoutas") of its Latin name is used by Pliny the Elder for an unknown animal (possibly hyenas) in Ethiopia; the term is derived from crocus, commonly used in the ancient world as a yellow dye. Literally, it means "the saffron-colored one". They are known for a chirping, birdlike bark that resembles the sound of hysterical human laughter. Though often labeled incorrectly as a scavenger, the spotted hyena is actually a powerful hunter, the majority of its nourishment being derived from live prey. Spotted hyena are the most common predator in sub-saharan Africa, living in savannah, dry woodland and desert habitats.

While Spotted Hyenas have no real predators (besides people), they are on occasion killed by lions, which eat the same foods and will often clash with hyenas over kills. With the development of television cameras that can "see" in the dark, male lions have now been imaged breaking the backs of hyenas. Although lions are much larger, hyenas will defend their kills if possible, and hyena packs have been known to kill lions if they outnumber them significantly.

Contents 1 Physiology 2 Reproduction 3 Hunting 4 Fighting 5 Life within the clan 6 References 7 External links

[edit] Physiology

Although hyenas bear some physical resemblance to wild dogs, they are members of a separate biological family which is most closely related to Herpestidae (the family of mongooses and meerkats). The spotted 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 to fear. An adult hyena's bite pressure can reach 50 kilograms per cm² (800 lb per square inch), allowing it to easily crush bone.

The spotted hyena ranges in size from 95 to 150 cm (3.1-5 ft) long along the head-and-body and stands from 75 to 90 cm (2.5-3 ft) at the shoulder. The normal weight range for the male, who is usually more lightly built than the female, is 36 to 55 kg (80-121 lb); whereas, the females normally weigh from 48 to 55 kg (105-121 lb)^[1]. Spotted hyenas in Southern Africa females can reach 70kg (154lbs). Some exceptionally large females have been in the ballpark of 90 kg (200 lb).The coats of spotted hyenas can range from sandy yellow or greyish to ginger or reddish in color. The coat is generally spotted, although these can fade with age.

Their front are sisy legs and 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 10 km/h (6 mph), waiting for it to become exhausted. They can then move in very quickly, at speeds of up to 50 km/h (30 mph).

Hyenas have extremely strong jaws and compared to their body size. 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, bones and even hooves. This, combined with their very strong stomach acid, results in them having crusty white droppings (from all the bone meal). Since they will eat carcasses, their digestive system deals very well with bacteria.

Hyenas are highly intelligent predators, and some scientists claim they are of equal intelligence to certain apes..^[2]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..^[3]

[edit] Reproduction

The female Spotted Hyena's urogenital system is unique among mammals: there is no vagina, and the clitoris is as large and as erectile as the male's penis - only the shape of the glans makes it possible to visually tell the sexes apart. The female urinates, mates and gives birth through this pseudo-penis (it dilates for mating, the opening widening to admit the male's penis). It was thought that the development of this structure depended on a masculinisation process triggered by the action of androgens on the female fetus, but experiments with anti-androgens show that it still forms in the effective absence of the hormone, so it is now ascribed to normal morphogenesis and sexual mimicry. Since it is impossible to penetrate without the female's cooperation, female hyena have full control over whom they choose to mate with.

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 labour times involved; in the wild, survival rates of females seem to fall sharply around the age of first giving birth, suggesting that the process is hazardous for the mother also. This 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.

[edit] Hunting

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 may 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 manner. The spotted hyena is predominantly 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. Their most commonly selected prey are wildebeest and zebra, both of which the hyenas hunt using different techniques.

Like dogs, but unlike some other animals in the same habitat, hyenas do not kill their prey directly. Having been chased 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 the hyena can begin eating immediately, which lessens the probability of the kill being lost to another predator. Hyenas kill small prey by crushing the skull with their jaws.

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. Other prey includes gazelle, impala, topi, eland,cape buffalo and rhino and elephant calves.

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.

[edit] 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, leopards, brown hyena 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.

[edit] 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. Clan life is centered around a communal den, however only cubs live within the den itself. Each clan is permanent social group called a fission-fusion society. 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. The society is highly structured, with dominance relationship between the matrilines (the groups of females descended from a single mother) that endure for generations. Social behavior is very complex, involving frequent alliances and shifting social ties. In this hyena are more similar to many old world primates than they are to other social carnivores.^[4]Male hyenas, which are usually smaller and less aggressive than females, often leave the clan when they are about two years old, while females stay within their birth clan.

Subordinate members of the clan lick the pseudo-penis of a higher ranked female as a sign of submission. The matriach'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.^[5]

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)

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.

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.

[edit] References

• Hyaena Specialist Group (1996). Crocuta crocuta. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006.

• Androgens and the Role of Female "Hyperaggressiveness" in Spotted Hyenas (Crocuta crocuta) Wolfgang Goymann, Marion L. East, and Heribert Hofer (pdf) - 'Androgen-independent mechanisms are likely to also play an important role, as treatment with anti-androgens during fetal development did not produce females without a pseudo-penis (Drea, Weldele, Forger, Coscia, Frank, Licht, and Glickman, 1998).'

• [http://www.current-biology.com/content/article/fulltext?uid=PIIS0960982206023165

[edit] External links

• http://hyenas.zoology.msu.edu/# The research of Kay Holekamp and her students at Michigan State University focuses on mammalian behavioral development and its physiological substrates; investigating how social, ecological, and endocrine variables interact during an individual's early development to influence its subsequent behavior and its reproductive success as an adult.

• Quirks & Quarks (science radio program)