The spotted hyaena is Africa's most successful large carnivore and arguably it's most interesting one as well. Its success is largely due to the fact that it has mastered the two main methods carnivorous animals use in procuring food: scavenging and hunting.

The spotted hyaena is best known as a scavenger and has evolved several adaptations to achieve this. It is equipped with a formidable set of bone-crushing teeth and possibly the strongest jaws of any animal. It also has a highly efficient digestive system enabling it to assimilate the organic matter in bone. This enables it to cash in on the remains of other large carnivores' kills and to reach the highly nutritious marrow locked up in the leg bones of animals like impala, wildebeest and even buffalo. This is something that no other animal - except the closely related brown and striped hyaenas - can do.

In addition to these feeding adaptations the spotted hyaena has the ability to travel large distances in its search for food - 70 kilometres in a night are well within its potential. The loping gait so characteristic of this species is an energy-efficient way of covering the ground necessary for a scavenger. On top of this it has a sense of smell to rival even the most highly bred bloodhound. This enables it to locate carrion at some distance.

Most people still imagine that spotted hyaenas procure most of their food by waiting patiently at lion kills for the so-called "King of Beasts" to depart after eating its fill. This of course happens. However, on more than a few occasions a very different scenario is played out and the lions have to abandon their kill far earlier than they would have chosen to do.

The first time I saw this was in the Kalahari where I spent many years studying hyaenas. One night I followed an old female spotted hyaena through the dunes until she came to a lioness feeding on a freshly killed gemsbok. After pacing up and down for a few minutes at a respectful distance from the lion and her kill the hyaena began to whoop - that beautiful, melancholy call so characteristic of the African night. However, instead of the six or seven whoops that hyaenas usually give, she whooped 17 times.

Within two minutes there was a reply and soon three other members of her clan came running up to her. After performing the elaborate meeting ceremony of the spotted hyaena, the four animals closed ranks and advanced on the lioness and her kill. With their short manes bristling, they uttered a variety of lows, whoops, and hoot-laughs - fighting talk in hyaena language. As they neared the lioness she started to growl. When they were five metres from her she lunged at them. However, they were not deterred and kept advancing until the lionesss' nerve broke and she bolted, leaving the kill to the hyaenas.

If hyaenas outnumber lions by about four to one and if there are no adult male lions present the lions are very likely to lose their carcass. On some occasions the reverse may take place. During the 1960s Hanns Kruuk found that in Tanzania's Ngorongoro Crater, 84% of the carcasses fed on by both hyaenas and lions were scavenged by lions from the hyaenas!

The spotted hyaena normally hunts at night and those of us who have had the opportunity and privilege to watch them hunt have witnessed some amazing events, for it is not only the sick, very old or new born that fall victim to the hyaenas' strength, speed and cunning, but also healthy, full grown prey such as wildebeest, gemsbok and zebra.

Hyaenas catch their prey by running them down at about 50 kilometres per hour in chases that may last three kilometres or more. In the Ngorongoro Crater spotted hyaenas kill 90% of their food; in the Kalahari 73%; in the Serengeti about 55% and in the Kruger National Park perhaps 30 - 40%. The ratio of scavenging to killing is dependent on the availability of carrion.

The size of the hyaena hunting groups depends to a large extent on the prey being pursued. The largest groups are found hunting eland and zebra where the average group size is 11. On the other hand, wildebeest are usually hunted in groups of three. In the case of gemsbok calves, Kalahari hyaenas are just as successful in hunting them on their own as they are in a group of six. Of 55 encounters I saw between spotted hyaenas and gemsbok herds with calves, 40 (73%) were successful in that the hyaenas managed to kill a calf, a success rate surpassed by very few other carnivores of comparable size pursuing similar prey.

Any study of the impact of predators on prey that does not include the spotted hyaena will give a very false picture of the true state of affairs. Not only are the hyaenas efficient hunters, they are very often the most numerous large carnivore in the area.

Together with the lion and the African wild dog, the spotted hyaena is one of the three truly social large African carnivores. Their social groups are called clans. Clan numbers and the size of their territories vary markedly depending on the amount of food available in the area. In the arid, prey-poor Kalahari, five to 10 adult spotted hyaenas may inhabit a territory of over 1,000 km2.

In the phenomenally productive Ngorongoro Crater, clans of up to 80 individuals live in territories as small as 40 km2. The members of a clan do not always stay together; a spotted hyaena may be on its own tonight, with three members of the clan tomorrow night and with ten others the next night.

Females remain with their natal clan for life. All males leave at about two years of age and go off to find their fortune in another clan. The females are arranged in a hierarchy in which daughters inherit their mother's status. Within a clan the females form coalitions around their mothers. These may eventually get so large that a fission in the clan takes place. The less dominant coalition breaks away and sets up its own territory somewhere else.

The immigrant males are also arranged in a hierarchy, but the highest ranking male has a lower status than the lowest ranking female. Females are larger than males and have mimicked the males' reproductive organs so that it is difficult to tell the sex of a spotted hyaena. The female has a pseudo-penis and pseudo-testes! This mimicry has been incorporated into the meeting ceremony. Two hyaenas stand head to tail, lift the inside hind leg and mutually sniff at each other's reproductive organs. In essence the individuals are exposing their most vulnerable parts to the other's lethal teeth. Only two animals that know and trust each other well will dare do this. It helps to reinforce the close bonds that exist between members of a clan that often co-operate in dangerous activities such as mobbing lions and defending the territory against intruders.

The focus of activity in a spotted hyaena clan is the communal den. The females keep their cubs together but, unlike lions, do not suckle each other's cubs. The den holes are small, only large enough for the cubs to enter, and thus provide ideal refuge when the adults are out hunting.

Females give birth to only one or two cubs. These are born with their eyes open and canine teeth fully erupted. Within minutes they often indulge in a protracted and serious fight that may lead to the death of the weaker of the two. This is particularly so if both cubs are female.

For about the first nine months of their lives the cubs stay at the den and their only form of nutrition is their mother's milk. Spotted hyaena females produce the richest milk of any terrestrial carnivore. Their dominance ensures that they have priority at carcasses so that they can eat quickly, convert the meat into milk and get back to the den to feed the cubs. Amongst the females, dominant animals have higher reproductive success than their subordinates.

This short account of the life history of the spotted hyaena gives only a superficial glimpse into a fascinating world. So, next time you see a spotted hyaena remember that you are looking at an animal superbly adapted to play a versatile and important role in the ecology of the African savannah and one that has a highly complicated social system.

Gus Mills is a specialist scientist with the South African National Parks, and head of the Carnivore Conservation Group of the Endangered Wildlife Trust. He has spent over 25 years researching the world of the larger carnivores.

Hyaena Fact File

Distribution: Abundant throughout most of southern and East Africa. Usually the most numerous large carnivore in undisturbed ecosystems.

Habitat: Open plains, savannas and semi-arid desert scrub. Reaches highest densities in areas that have many herbivores.

Field Characteristics: Females (70 kg) are heavier than males (60 kg), but both stand about 0.85m at the shoulder. Massively built, off-white to brown in colour with dark, irregular spots. Ears round.

Sounds: A very vocal animal - the whoop call is one of the characteristic sounds of the African night. Also a variety of human-like laughs, giggles and cackles, a cattle-like low, and a harsh whine when begging.

Social System: Highly social, living in clans of up to 80 individuals. A strict hierarchy exists among both sexes, with females dominant to males. Clan territories vary from 40km2 to over 1,000 km2, depending on food availability.

Breeding Biology: Non-seasonal; 1-2 young born after a gestation period of 90 days. Twins are usually male and female, occasionally two males, hardly ever two females. Cubs are born with their eyes open and with unusually well developed teeth.

Published in Travel Africa Edition Five: Autumn 1998. Text is subject to Worldwide Copyright (c)