(ORDO NEWS) — For any normal person, the concept of “cannibalism” is perceived as something terrible and unnatural.
Therefore, for a long time, scientists were sure that this phenomenon, which they often observed in the animal kingdom, was caused by stress in captivity or unnatural laboratory conditions.
However, the more they began to learn about it, the more they became convinced that the practice of eating their own kind is a vital feature of nature – an adaptive strategy for the survival and reproduction of many species.
Most often it occurs in invertebrates and fish, but not only. Cannibalism is also characteristic of every major group of animals.
Cannibalism in the family
The most common type of cannibalism found in nature is the eating of their offspring by parents.
Typically, this happens when the baby is sick, deformed, or born in conditions where the mother cannot provide food for him.
Also, the child can become a valuable source of nutrition for the parent if it dies or cannot survive.
Eating their own offspring by parents is called filial cannibalism.
Species that engage in filial cannibalism include leopards, African lions, Tonkean macaques, and many types of fish. Surely lovers of aquarium fish have noticed this behavior in guppies.
Sometimes parents eat their offspring even before the birth of children, when they are in eggs. Egg cannibalism is nutritious and requires little effort.
For example, one study showed that female cichlids living in Central Africa carry eggs in their mouths. They sometimes consume more than three quarters of their own eggs and fry.
“If you are a cod and lay five million eggs, you have a food source right in front of you that is safe and nutritious,” says biologist Bill Schutt, who has been studying cannibalism in nature for a long time.
Cannibalism for one’s own offspring
Earlier we said that the males of polygamous insects go to various tricks so that the females produce their offspring, and not someone else’s.
For example, Drosophila flies “put down” females after mating so that they no longer mate with other males. In the animal world, males also fight for their offspring, but more cruelly.
For example, male North American red squirrels kill and eat puppies that do not belong to them or whose paternity is unknown.
After the female loses her puppies, she goes into estrus and is ready for fertilization again.
After mating, the male drives away other males from her in order to be sure that the female will give birth to his offspring. Infanticide is also found in lions and chimpanzees.
Eating self kind for survival
In some species, siblings eat each other for a chance at survival. It is known, for example, that spadefoot toads lay their eggs in ponds, which sometimes dry up quickly.
To survive in such conditions, some tadpoles grow larger heads, as well as wider mouths and sharper teeth, than their omnivorous siblings. These cannibal morphs eat their own kind, which helps them grow quickly.
Some species start eating their siblings even before they are born. For example, female sharks mate with several males and carry offspring from several fathers in their two queens.
At the same time, inside the uterus, developing sharks begin to eat the remaining unfertilized eggs and even their embryonic brothers and sisters.
This leaves only two baby sharks, one in each queen. This behavior is called intrauterine cannibalism.
Sacrificing yourself
Spiders have another form of cannibalism called matriphagy, in which the newborns eat their mother. So the female velvet spider dissolves her own organs and regurgitates them to feed her offspring.
The last organs to liquefy are her heart and ovaries. Therefore, if a male spider eats a brood, the female, even with dissolved organs, can mate with him again and try to breed another offspring before she dies.
Many insect and arachnid fathers do not live to see their offspring at all. In the act of sexual cannibalism, females eat their partners in whole or in part during or after mating.
For example, male Australian redback spiders are often eaten by larger, more mature females. Some males specifically bend to be impaled on the fangs of their partner.
This provides the mother-to-be with healthy food and thereby increases the chances that her offspring will survive.
But this behavior is not unique to spiders. Female sagebrush crickets bite the males during mating and drink their nutrient-rich blood, known as hemolymph.
It also makes it impossible for a male to mate with another female. European praying mantis females generally bite off the head of the male, moreover, even before mating begins.
But the males have adapted to this – the absence of a head does not prevent them from fertilizing the female. This is how cannibalism benefits some living beings.
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