Information about Spotted Hyena

Spotted Hyena Fossil range: Pliocene - Recent
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 Spotted Hyena range

The Spotted Hyena, or Laughing Hyena, (Crocuta crocuta) is a mammal of the order Carnivora. They are moderately large, terrestrial carnivores native to Africa.

They are best known for croaking, 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 hyenas are the most common predator in sub-saharan Africa, living in savannah, dry woodland and desert habitats.

Anatomy and reproduction

Anatomy

Although hyenas bear some physical resemblance to the Canidae, they are in fact members of a separate biological family which is most closely related to Viverridae. The spotted hyena is the largest current member of the family Hyaenidae, and the last remaining member of the Crocuta genus, which once included the larger Cave Hyena. It is thought that the ancestors of the spotted hyena branched off from the true hyenas (striped hyenas) during the Pliocene era, 5.332 million to 1.806 million years ago. It ranges in body length from 95 to 150 centimeters (3.1-5 feet), and stands from 75 to 90 centimeters (2.5-3 feet) at the shoulder. In East Africa, the normal weight range for the male (who is usually more lightly built than the female) is 36 to 55 kilograms (80-121 pounds); whereas, the females normally weigh from 48 to 55 kilograms (105-121 pounds). They tend to grow larger in Southern Africa, with females often reaching 70 kilograms (154 pounds)^[1]. Some exceptionally large females have been in the ballpark of 90 kg (200 lb).

The fur's background colour is a cream to light brown, with irregular dark spots that fade with age. The muzzle is black. They have long, heavily muscled necks, lined with a coarse mane of reversed fur which protects them from bites and scratches.

The forequarters are more heavily built than the hindquarters, giving the hyena a distinctively sloping bear-like gait. Hyenas are built for endurance, possessing a very large heart which allows them to trot at 10 km/h (6 mph) without tiring. During chases, hyenas have been clocked at running speeds of up to 50 km/h (30 mph) for over 3 km. They are good swimmers, capable of controlling their buoyancy and walking at the bottom of pools whilst holding their breath.^[2]

Spotted hyenas mark their territories by excreting an oily, yellow substance from their anal glands onto surrounding bushes and grass. To do this, the anal pouch is turned inside out, or everted. The anal glands are everted also as a submissive posture to dominant hyenas. Scent marking is also done by scraping the ground with the paws, which deposits scent from glands on the bottoms of the feet.

Hyenas have extremely strong jaws in relation to their body size. In 2005, Dr. Brady Barr of the National Geographic measured the bite forces of many different animals, including spotted hyenas for the documentary Dangerous Encounters: Bite Force. A one year old cub had a bite measured at 273 kilograms (603 pounds) of force, leading to the postulation that a full grown adult could bite at over 453 kilograms (1,000 pounds).^[3] This mandibular power, combined with its large pyramid shaped molars allows it to easily crush bone, even those of elephants^[4]. An experiment conducted in 1955 showed how the spotted hyena easily outclassed the much larger brown bear in bone crushing ability.^[5] It is often asserted in television and print that hyenas have the most powerful bite for their overall body mass when compared to other animals, although there is no scientific basis for this claim. ^[6].

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 results in them having crusty white droppings, due to the amount of calcium they ingest. The hyenas digestive system is so efficient, it can even derive nourishment from mummified corpses.^[7] There are even reports of hyenas entering campsites and consuming aluminium pots and pans.^[8] Undigestible parts are vomited in the form of pellets.

In the wild, the spotted hyena has an average lifespan of 12 years. In captivity, it can be extended to 25.

Reproduction

The female Spotted Hyena's urogenital system is unique among mammals: the clitoris is elongated to form a fully erectile phallus, the vaginal opening is at the tip of this phallus. - only the shape of the glans at the tip of the phallus makes it possible to differentiate the sexes. The female urinates, mates and gives birth through this pseudo-penis. Since it is impossible to penetrate without the female's cooperation, female hyena have full control over whom they choose to mate with. The male hyena's penis lacks a baculum, a bone found in the genitals of most mammals.

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, and in the wild, it is estimated that 10% of first time mothers die during labour.^[9] 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^[10]. 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. ^[11] 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.

Communication

Vocalizations

The spotted hyena is among the most vocal African mammals, with over 11 different sounds being recorded.^[12]

• Groans/soft squeals – Often exchanged during greeting.
• Whoop – A contact call, varying in pitch and intensity. A fast whoop is a rallying cry given by excited hyenas during conflict or at a kill site. Apparently, calls emitted by males are usually ignored. Calls emitted by females however are responded to immediately.
• Lowing – A sound made by impatient hyenas, usually when waiting for their turn at a kill.
• Grunting – A very low growl with the mouth closed that accompanies aggressive behaviour.
• Growling – A deep, resonating rumble made by defensive hyenas threatening to bite.
• Rattling growl – A low-pitched, soft, staccato grunt given as an alarm call.
• Giggling – A high pitched, cackling laugh, typically emitted by hyena being chased; expresses intense fear.
• Yelling – A roaring scream voiced by hyenas attempting to escape attackers.

Body language

• Phallic inspection – An affectionate greeting ceremony between clan members, usually initiated by lower ranking individuals. After mutually sniffing the nose, mouth, head, and neck, the 2 hyenas stand head-to-tail and sniff/touch each others extended phallus for up to 1/2 minutes with their back legs cocked. This greeting is performed by both sexes at the age of one month onwards. Adult males rarely greet with females in this manner.
• Social grooming – Licking and nibble-grooming between mothers and offspring, though rarely between adults.
• Courtship – The male approaches the female from behind with his head bowed and penis extended. He will paw the ground behind her, depositing his scent with his toe glands.^[13]

Social structure and hunting

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.^[14]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 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.^[15]

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.^[16] 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.

Dietary habits

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.^[17]

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.^[18]

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^[19]. 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 kilometres, 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.^[20]

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.^[21]

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.^[22]

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.

Relationship with lions

The relationship between hyenas and lions in areas where they coexist is unique in its complexity and intensity. Lions and hyenas are both apex predators which feed on the same prey, and are therefore in direct competition with one other. As such, they will often fight over and steal each others kills. Though it is popularly assumed that hyenas are opportunistic scavengers which profit from the lion's hunting abilities, it is quite often the case that the reversal is true. In Tanzania's Ngorongoro Crater, the Spotted Hyena population greatly exceeds that of the resident lions, which obtain a large proportion of their food by pirating hyena prey.

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 heathly adult males, even single ones, are generally avoided at all costs.

Historical perceptions

The Greek philosopher Aristotle was noted to have first challenged the condemnations directed toward the hyena's supposed hermaphroditism. It is however doubtful he had any first hand experience with spotted hyenas to begin with, considering his physical descriptions match those of the striped hyena which does not share its spotted cousin's sexual anomalies. 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".

Early in the Christian era and continuing through the middle ages, two charges against hyenas emerged: that they could swap gender, which was a morally unacceptable practice, and that they feasted upon human corpses, digging up graves. The former was symbolically linked to the Jews and reflected the anti-semitism of this extended period, while the latter was threatening to many human traditions and persists to the present day. Sir Walter Raleigh, in his History of the World believed that hyenas were not present in Noah's Ark, considering he believed them to be mixed animals like Mules, and thus could easily be recreated.

1656 was the year of the first predator culling legislation in South Africa. The hyena was known as "wolf", and rewards of up to four realen were given to those who managed to kill them.^[23]Predator culling was a common practice in the early African game reserves until the mid 20th century. In the Kruger National Park between 1903 and 1927, 18,428 predators were killed in an effort to protect game herds. Spotted hyenas accounted for 521 of the killed predators.^[24]

African attitudes toward spotted hyenas are little better than those held in the Western world. The Kaguru of Tanzania and the Kujamaat of Southern Senegal view hyenas as inedible and greedy hermaphrodites. A mythical African tribe called the Bouda is reputed to house members able to transform into hyenas.^[25] Belief in "Werehyenas" is so entrenched within the traditional lore of the Bornu people of north-eastern Nigeria, that their language even contains a special word bultungin which translates as "I change myself into a hyena".^[26]

Perceptions of the spotted hyena today are little better than they were before the 20th century, despite extensive studies by Hans Kruuk and Jane Goodall showing the species more admirable traits. Frederick Selous noted that the spotted hyena shared some of what were considered to be the more noble traits of the wolf, and criticised those who lauded the wolf while downplaying the spotted hyena.^[27] A trio of spotted hyenas; Shenzi, Banzai and Ed was featured in the successful 1994 Disney film The Lion King. Several artists from the Disney studios stayed at the hills above the Berkeley campus of the University of California, where for two days they observed and sketched the colony of hyenas kept at the Field Station for Behavioural Research. Dr. Laurance Frank, who had organised the visit, previously studied hyenas in the Masai Mara reserve for 15 years and expressed a strong desire that the animals be portrayed positively. Although the artists explained that the script required the hyenas to be allies to the story's main villain, they claimed they would do their best to make them appear more comical than evil.<ref name="AP" /> Dr. Frank has expressed a deep dislike for the resulting film, on account of the fact that the portrayal of hyenas was not a new one. The hyenas were not particularly appealing characters, and were shown as clumsy, maniacal creatures who'd do anything for food. ^[28]

Attacks on humans

Spotted hyena attacks on humans are considered to be common, with dozens of deaths reported each year.

In Sudan, due to a lack of proper housing, children often have no choice but to sleep outside at night, thus becoming vulnerable to nocturnal predators. A death census was taken in 2006, which showed that in addition to being at risk to human trafficking, “More than 280 orphans have died in our community of Nyamlell, Sudan this year alone, simply because they do not have a safe place to sleep at night.” Hyena attacks were shown to be the number one cause of death.^[29]

In Mozambique, hyena attacks are said to be even more common than lion attacks. In one year, hyenas had attacked 52 people, 28 of whom were killed.^[30]

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

External links

• http://hyenas.zoology.msu.edu/ The research of Dr. 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.
• http://www.hyaenidae.org/the-hyaenidae/spotted-hyena-crocuta-crocuta.html The IUCN Hyaenidae Specialist Group page on spotted hyena.
• Quirks & Quarks (science radio program)