Cannibalism is an ecological relationship observed when food is scarce and at the time of reproduction of some species.The ecological relationships are interactions that occur between living beings, which can be of the same species or different species. When it occurs between individuals of the same species, we say that it is an intraspecific relationship and when it occurs between individuals of different species we call it an interspecific relationship .The intraspecific relationship, as well as the interspecific relationship, can be harmonic or disharmonious . We call harmonic relationships those in which all individuals benefit from the interaction. The disharmonious , in turn, are characterized by harming one of those involved.
The cannibalism is an example of disharmonious intraspecific relationship . In this relationship, an individual of the same species kills and feeds on another. When death and the ingestion of organisms of different species occur, we say that there was a predation.
Cannibalism, for most species, is a rare behavior , but for some it occurs normally. Most of the time cannibalism occurs in populations that have a large number of individuals, however the amount of food is scarce . Sometimes this relationship also happens at the moment or after fertilization.
In species such as spiders, fish, rats and praying mantis cannibalism is common. The latter stands out for having his behavior well known. The female of the praying mantis kills the mate during the mating, even before the end of the copulation the female begins to feed on the male, eating him completely. This act is important, as it provides necessary food for the female to develop her embryos and lay her eggs.
Another well-known case is that of some species of shark, which exercise intrauterine cannibalism . In these species the pups feed on the others still inside the womb. The mangona shark is one of the species that exhibit this behavior.
Lately, there has been an increase in cannibalism among polar bears . According to researchers, the increase in attacks between individuals of the same species has increased due to global warming. Bears feed mainly on seals, when they rise to breathe between the ice slits, but as the ice has melted at a high speed, seals do not appear as often; thus, bears are having to look for new food alternatives.