Dave Taylor's African Safari: Trophic Level II - The Herbivores - African Elephant

Trophic Level II - The Herbivores
African Elephant
Page 20

Weight: 2 200-3 500 kg (4,850-7,700 lb.)female, 4 000-6 300 kg (8,800-13,900 lb.) male

Status: Endangered, but due to increased protection, population is stable and increasing in some areas. Poaching remains a threat that, should the price of ivory increase again, could bring about a severe drop in elephant numbers.

Habitat: Elephants are able to exist in a wide variety of habitats and can wander as far as 80 kilometers (50 miles) from water. They are found in the deserts of Namibia, the rain forests of the Zaire Basin, in grasslands, woodlands, scrub brush and on the upper slopes of Kilimanjaro.

At one time, the African elephant's range covered virtually the entire continent, but it has been greatly reduced due to the demands of agriculture and poaching. Today, elephants are still fairly widespread in Africa but they are confined to parks, reserves and areas unsuitable for farming.

In the Serengeti-Mara ecosystem, elephants were largely absent from the grassland portion of the range until the 1960s. As the human population expanded and poaching put pressure on unprotected populations, the herds were forced into the confines of the park. In the Serengeti, the population remained low until the late 1980s but in the Mara, it increased rapidly. This was in no small part due to uncontrolled poaching rings working in the Serengeti. The Mara was much safer and better protected and Tanzanian elephants emigrated north.

Today, with better policing, the elephant population in the Serengeti is growing.

In this ecosystem, elephants will retreat into swamps and forested areas in the dry season and expand their ranges into the grasslands during the wet season. It is believed that the bush elephant (the race seen in the Serengeti and most National Parks and Reserves), has only expanded its range into grasslands in the last 20,000 years. Before that time, African elephants were forest animals and much smaller in stature. The forest elephant of today is believed to be identical to the race that gave rise to the bush elephant. Forest elephants are a meter shorter at the shoulder and weigh much less (900-3 000 kg/1,980-6,600 lb. female, 1 200-3 500 kg/2,645-7,700 lb. male).

Food: African elephants exploit whatever vegetation is most abundant and nourishing in their environment. They are both grazers and browsers. The chart below shows their preferences:

African Elephant Food Selection
Feeding Level		Dry Season	Wet Season
Above Head
(branches and bark)	Browse	10.30%	1.80%
3.5%
Elbow to Top of Head	Browse	15.80%	10.40%
(bushes)
11.5%
Ground to Elbow	Grass	34.40%	69.70%
(grass, shrubs and small trees)	Browse	39.70%	18.10%
85%

A large bull elephant can actually feed higher into a tree’s branches than a giraffe can. They have even been seen to rear up on their back legs to extend their reach. Elephants gather food with their trunks. They can pull down a branch or twirl around a tussock of grass and yank it free. Tusks are also used to pry loose bark, dig a pit in mineral rich earth or to help break off a morsel. Many of the fever trees and baobabs bear scars as mute evidence of the elephants’ passage.

As the chart shows, grass makes up a substantial part of the elephant's diet year round, but especially in the wet season. It is then that grass is at its most nutritious.

Elephants consume 5% of their body weight or up to 150 kilograms per day (330 lb. per day). It takes 12 hours for the food to pass through the animal.

A large percentage of that intake is wasted (about 55%) and is passed out in the form of droppings (pictured left). Elephant dung is therefore rich in undigested nutrients that many animals are quick to exploit. Dung beetles and wart hogs both make use of this material as a source of food.

Perhaps more important to the ecosystem are the large numbers of undigested seeds that find an ideal place to sprout and germinate in the elephant dung. It is felt that the mixing of African flora (vegetation) is due in large part to elephants carrying seeds from one location to another and then "planting" them.

Elephants certainly will destroy trees as they feed and strip bark off of them, but they also spread the population around and start new colonies. In the past, this was very important to the health and diversity of the continent's flora and fauna. Today, however, there is a real fear that elephants are more destructive to the environment because they can no longer range over vast areas.

In the past, a herd would feed in an area and then move on, leaving thousands of seedlings in their wake. It may have been several years before they returned to the area, by which time the seedlings had a chance to grow and mature. Due to the restricted range imposed by park boundaries and human settlements now, elephants can no longer migrate and they often eat the seedlings before they are fully grown .

The Serengeti ecosystem is so large that this is not a serious problem yet. It was becoming an issue in the Mara, however, when elephants were forced to immigrate from the Serengeti into the Mara due to the pressures of illegal poaching in the Serengeti. That has eased now and the herds wander more freely from park to park.

Social System: Elephant society has been well studied in recent years. They live in a matriarchal clan society. A basic unit consists of an older cow, her daughters and their offspring. Typically, there are about a dozen animals in the unit. When herds get larger, they split into two groups but, even then, they remain close and will spend at least half of their time together. Often, a sister herd will feed within a kilometer or two of the other. Even at that distance, they communicate.

Elephants are known for their trumpeting calls but much of their communication occurs using sounds so low that human ears cannot hear them. If you stand close to an elephant making these calls you might feel the vibration in your chest the same way you feel the vibrations of a base drum or tuba. These sound waves are called subsonic or infra-sonic and are lower in tone than the lowest note on a piano or tuba.

Subsonic rumblings made by an elephant are audible to another elephant that is two, three or even four kilometers (1.2 to 2.4 miles) away. The elephant’s large ears are ideal for hearing these sounds. Analysis of the calls shows that they have a "language" all their own. Some calls mean, "here I am and I am fine." Others advertise to bulls that a cow is in estrus. Some convey stress and danger.

These calls help elephants to find each other and also to avoid each other if they choose. For example, a herd that is not a clan group may wait some distance from a waterhole while another group drinks. When that group is finished drinking, the distant group moves in to take its turn. They do this even though they cannot see each other!

When elephant herds meet each other there is much commotion. They greet each other and use their trunks to reaffirm their kinship. Elephants touch each other in much the same way humans use their hands when greeting. An elephant's trunk is really a combination of its upper lip and its nose. It is a very sensitive organ, consisting of between 50,000 and 100,000 muscles.

It takes an elephant calf several years to fully learn to uses its trunk. Like all babies, it uses its mouth and not its trunk to get milk from its mother's teats. As it grows, it learns to pluck individual leaves from a tree, toss sticks, throw mud on its back and communicate with other elephants.

Greeting elephants will place their trunk in the mouth of another. This helps them to recognize the other animal and they may also get a sense of what it was feeding on, and perhaps assess its health.

Elephant clans will regularly cross each other's paths and will sometimes mass in herds of up to 300. In the past, such gatherings may have held several thousand animals.

Elephant clans are much like human clans. There is the family unit of closely related individuals. Then there is the aunts’ family unit (s) which is only slightly removed from the family unit. More distantly related will be the second cousins’ group which share the range but meet up with the "family" unit less often. All of these may share all of, or part of, the same range. Other neighboring clans, whose ranges border that of the first clan, will seldom meet.

All of the family groupings are led by an old female. Elephants live 50 to 60 years and the older elephants remember the routes to food, water and other places that help the herd survive. For example, a severe drought may happen once every ten years. It is during these stressful times that the memory of a distant and seldom visited waterhole becomes crucial to the survival of the herd.

The life span of an elephant is determined by its teeth. Elephants have evolved huge molars in order to grind their food up. They get six sets of teeth during their lives. When the last set is worn down, they slowly starve, unable to process the food around them. The length of time a tooth lasts is dependent on the type of food an elephant eats. If the food is gritty or sandy the grains wear down the tooth more rapidly.

When a cow becomes too old or feeble to lead the herd any more, she falls behind or leaves the herd on her own accord. Another old cow will replace her. When an elephant dies, other elephants will stop and investigate the remains, picking up tusks and bones with their trunks. Scientists can't help but wonder if they remember the individual.

Behavior: A cow elephant will continue to have calves until she is around 45 years old. She conceives her first calf when she is 10 or 11. Gestation is 22 months in length so that most cows become parents when they are in their early teens. Reproduction is delayed when there is poor food or other stressful factors.

A cow seeks a spot on the edge of the herd to give birth. Often, another cow will accompany her and provide a safeguard for her against predators. The birth weight of the calf is 120 kilograms (260 lb.). The calf can stand within an hour or so of birth and quickly seeks out its mother's teats. Its mother will touch the calf and stroke it, exploring it, getting to know it. The calf will not wander far away. For the first year or so, it stays close to mother's side. At times, it seeks refuge from the hot sun by standing and walking under her. (All ages of elephants have sensitive skin and use mud as a sun-block. This habit explains why elephants appear to come in so many different colors. They "wear" the color of their range's mud.)

Even a nine year old is seldom further than 5 meters (16 feet) from its mother’s side even though it has been fully weaned for over five years. Elephants just seem to like each other.

A newborn calf is a cause for some excitement among the herd. When the cow is in labor, another cow will normally accompany her some distance away from the rest of the herd. After the birth, other elephants will come and visit, exploring the new arrival with their trunks.

As the calf grows, it will have several babysitters if it is lucky. This will happen if there are other, older calves in the herd. They are known as allomothers and they serve an important function. They are playmates and companions for the new calf. By filling this role, they free the mother to go and feed in peace and quiet. Calves with allomothers have a higher survival rate than those without.

A cow calf will remain with her mother's herd, but for a bull, life changes when he hits puberty at around 12 or 13 years old. As his hormones kick in, he begins to flirt with the cows in his herd. These are all, of course, either his sisters, aunts or mother. He becomes very irritating and is soon chased off. Most males leave their natal herds by the time they are 14 years old. (Author’s note: the youngest recorded departure of a male is 9 years. The latest was around 18 years old.)

These bachelor bulls are big enough to ward off most predators and either wander alone or seek out other bulls. A typical bull herd will have between two and fourteen such animals of varying age. They may occasionally gather in bigger groups.

Bulls wander over larger ranges than cows when they are seeking mates. For the better part of the year, they remain in areas where there is enough food and water to support them. Such areas are often places where cows with young calves dare not go. For example, no cow-calf herds feed on the floor of Ngorongoro Crater due to the large numbers of predators that live there. About 70 bulls use the crater floor, leaving it only to seek mates.

In a healthy, stable population, bulls will first make a serious attempt to mate when they are about 25 years old. They are now much larger and young cows find them attractive. These young bulls are more likely to come across a cow as she enters her estrus period but they are unlikely to breed. Older bulls, 35 years and up, are bigger still and will chase off the younger ones and claim breeding rights. Elephants are not territorial. Size and dominance determine breeding success.

The most dominant bulls are those that are 45 years old and older. At this stage in life, the bulls enter a yearly period of musth. Musth is a state of heightened aggression and sexual activity. Musth begins when the elephants are in their late 30s but does not become predictable until they are in their 40s. It lasts for a period of three months during which the bulls go off in search of cows in heat. They eat less food during this time and their behavior changes. They walk in a peculiar way with their head held high. Their penis dribbles a greenish, strong smelling liquid and their temporal glands secrete more fluid than usual.

A bull in musth will dominate bulls to which he would give way ordinarily. Other bulls recognize his aggressive state and give way to him.

Fights between musth bulls have resulted in the death of one of the combatants.

Females find musth bulls very attractive and will fight for their attention if there is more than one female in heat at the time. Musth bulls fertilize the majority of females. After the musth passes, the bulls return to their smaller home ranges and rejoin other bulls.

Musth periods for older bulls are predictable but severe droughts can cause the bulls to miss this period. The same conditions will cause cows not to ovulate. In this way, nature imposes a natural form of birth control on elephants (and other species too). If conditions are such that a female does not get enough food to sustain a pregnancy, she does not enter estrus.

Predators: Next to humans, lions are the main predators of elephants, and in one southern African reserve at least, lions regularly take immature animals as prey. It takes several lions to isolate an elephant, especially a calf. When danger threatens, the herd will form a circle and place the young inside. Elephants will also keep close together when they cross open country.

Faced with a circle of enraged cow elephants, lions usually break off the hunt. However, if they do manage to separate an animal, they attack it in much the same way wolves attack a moose (or wild dogs a wildebeest). In both cases, the victim is bitten repeatedly until finally it is weakened by the loss of blood and can no longer defend itself.

Lions will begin feeding on the hind quarters and soft abdomen of an elephant long before it actually dies. Fortunately, the poor elephant enters a state of shock and probably feels little pain.

Dave Taylor's African Safari - Book 3: Trophic Level II - The Herbivores (Standard Version)
Copyright � 1999 Dave Taylor & James Cash