|A cannibal is an animal that feeds on others of
its own species. This is not an unnatural characteristic: around 140 different
species show cannibalistic tendencies under various conditions. Cannibalism
is most common among lower vertebrates and invertebrates, often due to a
predatory animal mistaking one of its own kind for prey. But it also occurs
among birds and mammals, especially when food is scarce.
What is Cannibalism? The word cannibalism comes from the name of an island race called the Cannibals. This warrior tribe had the habit of feasting on their enemies killed or captured in battle. The name has since been applied to any animal that eats others of its own species. There are two kinds of cannibals: active and passive. Active cannibals hunt and kill their own kind before eating them. Passive cannibals feed on already dead members of their own species. Active cannibalism takes various forms. In some species, for example, it occurs only between animals of one generation, while among others it is common between adults and their offspring.
Why do Animals Become Cannibals? Generally, cannibalism is a particular form of feeding behavior where a predatory species preys upon or simply eats animals of its own kind. Cannibalism is not the result of a predators efficiency, but the opposite. Few of the top flesh eaters, such as wolves and tigers, ever eat those of their own kind. Even those that do, like the spotted hyena, are usually passive cannibals. Cannibalism is more common among lower animals such as the preying mantis, when they may not be able to distinguish between relatives and prey.
The Benefits of Cannibalism: Cannibalism may seem purely destructive, but it can, in fact, be quite beneficial. Clearly, a voracious cannibalistic species would rapidly eat itself out of existence. When cannibalism occurs in response to overcrowding, for example, it can increase the species’ chances for survival. A population rising too rapidly without restraints can eliminate its own food supply. During a harsh winter or drought, when food is scarce it is clearly to a species’ advantage for at least some of the population to remain well fed and healthy even at the expense of others, Among species that produce many offspring, such as frogs, cannibalism of siblings helps ensure that some young develop into adults, thus continuing the species. Cannibalism appears to be an inherited trait in some species.
Opportunistic Cannibalism: Many species of gull that nest in large colonies cannibalize eggs and young. When it is sporadic, this behavior may be a response to crowding, but some gulls throughout the breeding season live entirely on the eggs and chicks of their own species. The chief perpetrators tend to be males without young of their own.
Environmental Pressures: Some animals become cannibals when faced by certain environmental conditions. Mice and rats, for example, may turn cannibal when their colony population rises rapidly, and their naturally high reproductive rate results in a high mortality of young. Dead offspring may be eaten by the hungry and stressed survivors. This behavior is most often observed in animals kept under unnaturally cramped conditions in captivity but there is also evidence of cannibalism occurring in the wild under similar conditions. Among some bird species, parents or nestlings may eat the young when populations become dense, or food scarce. Young birds of prey often kill and sometimes eat weaker nestlings. Crows, too, may eat eggs and chicks of rivals to improve their own chance of successful breeding.
Infanticide: Cub killing among lions: Of the higher mammals, the lion shows the most definite cannibalistic tendencies. There have been many reports of male lions killing and then sometimes eating young cubs. In almost all cases, however, the male lion is prompted to kill the cub, not from hunger or population pressure, but by a need to safeguard his own offspring. In most cases, the young are killed but not eaten. This is better described as infanticide, the killing of young, rather than cannibalism.
This extreme behavior is linked to the fact that a female lion reproduces quite slowly, usually coming into season again only after her cubs have become independent. Also, the male has a short breeding period of only about three years. By killing any cubs and young lions already present, he both encourages the females to come into season and eliminates the chance of any rivalry against offspring he later fathers.
Primate infanticide: The males of several primate species, including the common langur, also practice infanticide. Bands of male langurs will attack a mixed troop, driving off the males and killing the offspring before mating with the females. Baboons also have been observed killing their young, and, like the lion, occasionally even eat them.
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