Trophic Level IV: Large Carnivores Spotted Hyena Page 8

  Hyaena crocuta

Length: 100-180 cm (39-71")

Tail: 25-36 cm (10-14’)

Weight: 40-90 kg (88-198 lb.)

Status: Not endangered overall but declining in some areas

Habitat: Spotted hyenas were once found in most of non-forested Africa. Because it preys on domestic livestock, it has been shot in much of its former range. However, it must also be said that this species is adept at exploiting human garbage and does well where garbage is common.

In the wild today, it is found in most protected or wild savannas, grasslands and open woodlands. It is found in all Acacia woodlands.

Food: Spotted hyenas were once believed to be scavengers that cleaned up the kills of other predators. This belief was based largely on observations made during the daylight hours. It was not until the 1960s, when Hans Kruuk began his studies in Ngorongoro and the Serengeti, that a true picture of the hyena's role came to light.

During the day, hyenas are often found surrounding lion kills. The assumption was that lions made the kill. Other observers found hyenas on a kill surrounded by lions. The assumption in that case was that hyenas had stolen the kill. Kruuk's nocturnal observations of hyenas presented an alternative picture. At least half the time, it was the hyenas that made the kill and the lions were scavenging from them.

Spotted hyenas are scavengers and will eat almost anything. They are also excellent hunters and can bring down wildebeest and zebra without much difficulty. They also prey on small gazelles, topi and even rhino and elephant calves. (In Ngorongoro Crater, where the hyena density is very high, the species often succeeds in killing rhino calves despite the cows’ attempt to fight them off. It may one day become necessary for rangers to interfere in the natural course of things and protect the endangered rhino’s offspring.)

Wolf-Like Killers

Hyenas are wolf-like in their hunting behavior. They are coursers and run their prey down. However, unlike wolves and wild dogs, the entire hyena clan doesn’t always participate in a hunt. Often, one hyena will head off to hunt while the others either go their own way or stay behind. Sometimes, a few will go off together.

However, if the hunters start closing on their prey, their wild whoops and laughter will bring others to perhaps kill the animal and certainly to help eat it.

Since spotted hyenas often select prey bigger than themselves, they must rely on running the animal down and then inflicting enough wounds on it to cause it to bleed to death.

Hyenas make better use of their kills than other predators do. Lions and wild dogs, for example, waste up to 40% of their kills. Hyenas have a digestive system that is so acidic that they can get nourishment from even the most unappetizing parts. A spotted hyena eats virtually all of its kill and can digest bones, hooves, horns and even teeth, parts that other predators ignore. Only the rumen contents and the horn bosses of large ruminants are ignored.

Hyenas bolt down their food rapidly and can reduce a wildebeest carcass to nothing more than a reddish-brown stain on the ground in less than 40 minutes. They usually consume 13 kilograms (29 lb.) of meat at a kill. Hyenas do not waste time fighting over food. It is every hyena for itself. Often, hyenas that did not participate in the hunt will hear the wild cackling and laughter and rush to join the feast. If those hyenas are from another clan, a fight might ensue for the right to the kill.

Social System: Spotted hyenas often live in large clans that defend a territory against other hyenas. Territories are only defended in areas where there are large numbers of hyenas living fairly close to each other. Ngorongoro Crater's hyenas display this kind of territorial behavior. A clan there consists of between 35 and 80 animals. Ngorongoro, however, is quite different from the Serengeti. Resident herds of wildebeest and zebra do not migrate and this allows clans to establish firm boundaries.

In South African studies, spotted hyenas that lived in arid areas with low populations of ruminants had territories that were so huge that defending them was impossible. Clans also tended to be very small with less than 10 members.

The Serengeti-Mara ecosystem is not as rich as Ngorongoro's or as poor as South Africa's arid region. It lies somewhere between these two extremes. Serengeti clans average 20 to 25 animals. They have territories but the boundaries are not well patrolled. Many clans leave their home territories and enter that of other clans where they may go unchallenged or undiscovered.

They do this because they must follow the herds on their migrations. Serengeti lions have a territorial structure that is far more rigid and keeps prides confined to their home ranges. When the Serengeti-Mara migration is not in their area, a hyena may have to travel 80 kilometers (50 miles) or more to hunt. Their journey will take them through several adjoining territories.

A Unique Society

Hyena society is unlike that of all other social carnivores; wolves, wild dogs and lions.

A hyena clan is led by a single female hyena. She competes with other females for this role and must fight for her right to lead. She also must show leadership qualities in battles with other clans and when harassing lions.

Males play a lesser role in hyena society. They help in the hunt but are not actively involved around the den. Their main function seems to be to mate with the female.

Hyena females may all have cubs and each female will have its own den in a communal den area. The communal den is an area where several related females will all have their dens. The area is often well trampled and pathways between dens may occur. Any cub can use any den it wishes when danger threatens. As soon as the danger is past, the cubs return to their own dens.

Cubs assume the status of their mother. A dominant female's cubs will dominate other cubs. The most subordinate's cubs will be picked on by other cubs and there is little the mother can do prevent it. Should she interfere in the aggressive play, she herself might be harassed by the more dominant cub's mother.

Cubs of the most dominant females will even bully adult males. Indeed, males are not welcome around the communal den and few visit it on a regular basis.

Female spotted hyenas will not nurse another's offspring. Cubs at the den rely entirely on their mother's milk. No food is brought to them.

Changing Sexes?

Spotted hyenas were once believed to change sex. Early observers believed that all hyenas started out life as male and then changed to females when they matured. This is not true but the truth is almost as remarkable. Female hyenas possess what scientists call a "false penis" that in almost every way mimics the male's. They also have what looks to be a scrotum as well. The effect of this makes it very difficult to tell a female from a male hyena.

What is the purpose of this elaborate visual illusion? Much of the greeting activity of spotted hyenas centers on sniffing each other’s genitals. The false male organ is displayed by lifting a leg for sniffing. This is a sign of appeasement, of accepting the "sniffer" as a more dominant animal. This also helps them recognize fellow clan members.

The "maleness" of the female hyena isn't just physical. She is larger and more aggressive than males. Females are 12% larger than males and dominate them. This aggression begins as soon as she is born. It is due to high levels of male hormones present in her body when she is a fetus. Throughout her life, these hormones cause her to develop the male-like organ and behavior. She has a higher level of testosterone than males do.

Behavior: Recently, researchers have uncovered an expectedly violent side to the behavior of cubs in the den. Cubs are aggressive towards each other and will fight. This in itself is not uncommon among animals with multiple births. Lion cubs and wild dog pups sort out a rank order before they are very old. Lion cubs and wild dog pups do not do any serious damage to their brothers or sisters.

Twins are common among hyenas. Spotted hyena cubs will fight with each other. These fights begin within minutes of birth. Hyena cubs are born very well developed and have sharp teeth. Surviving cubs often show the wounds from these battles. If the twins are the same sex, the battle often continues until one is dead. If they are opposite sexes, the fights end as soon as dominance is established.

The heightened amounts of male hormone in the female cub’s system make her more aggressive. Spotted hyenas are the only mammals known where one cub will (sometimes) kill another. About 25% of all cubs are lost to sibling rivalry during the first month of life.

Although the den site is large enough for an adult to enter, there are special chambers dug by the cubs that only an animal of their size can enter. This protects them from adult hyenas that might want to feed on them. Den sites may be used for generations. In some parts of their range, there are cave dens that may have been in use for thousands of years.

Spotted hyenas give birth all year long. The gestation period is four months. Such a long gestation period allows cubs to be well developed when they are born. Twins are common but a litter will range from one to four animals. Newborn hyena cubs weigh between 1 and 1.6 kilograms (3.5 lb.). They are not born in the communal den. Mother searches out and finds an unused aardvark den or digs one of her own. Two to six weeks after birth, the cubs are brought to the communal den.

Life of a Cub

Cubs are nursed six times a day at first. This is then reduced to three times a day when they are three months old. Each time they nurse they do so for an hour and a half. Cubs are not fully weaned until they are over a year old. By that time, they will have participated in hunts. Cubs that are being weaned have frequent temper tantrums where they vent their anger at their mothers. The cubs of the dominant female will visit nearby kills when they are as young as three months old. Cubs of other females will not do so until they are seven to eight months old. Female cubs stay with their mother's clan while males emigrate.

Young hyenas have darker spots than older ones. This makes it fairly easy to estimate the age of animals seen on safari. Older ones are often battle scarred and have torn ears.

Hyenas love to cool off in the heat of the day. If there is shelter around, the adults will head for it, leaving the pups to the den area. Thick bush is often used. They will also lie in water and muddy puddles.

Predators:  Hyenas are very competitive with lions. They steal food from each other. The success of defending or stealing a kill depends on a number of factors. First, it depends on how badly the hyenas want the meat. Are they prepared to wait until the lions leave? How many lions are there? The more lions there are, the more hyenas it will take to displace them. What sex are the lions? The presence of one large male lion may be enough to convince the hyenas to move on or to give up their own kill. Male lions just ignore hyenas or actively try to kill them. Many hyenas are killed by lions.

Wild dogs will usually be able to drive a hyena or even a number of hyenas away.

Leopards will take their kills in trees to avoid losing them to hyenas. If the leopard kill is found before the cat can get up out of the way, then the hyenas will claim it. Cheetahs bolt down their food and then depart the kill. They will not defend it. Jackals of both species steal brazenly from hyenas. They are fast enough and nimble enough to escape them. One jackal will harass a hyena while the other darts in for the food.

Hyenas will often locate a kill by watching vultures descend on it. They chase off the vultures and confiscate the meat.

(see also: Appendix IV: Comparison of Average Density of Lions, Spotted hyenas & Prey in Ngorongoro and the Serengeti)

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Dave Taylor's African Safari - Book 5: Trophic Level IV: Large Carnivores (Standard Version)
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