Cannibalism

Abstract/Summary

The act of cannibalism, the killing and consumption of all or part of an individual of the same species, occurs widely in nature, including bacteria, protozoans, invertebrates, and vertebrates, as well as humans. It plays a role in economically important pest populations and aspects of biocontrol. It is a serious problem for domestic animal and fisheries industries and in colonies of mice and rats used for medical research due to the crowded conditions under which these animals are often kept. Perhaps best known is the case of sexual cannibalism when the female kills and then eats its male mate during courtship and mating, as in some species of praying mantids. Cannibalism can greatly influence populations regulated by density-dependent factors. Cannibalistic populations may persist when food is severely limited, whereas a noncannibalistic but otherwise identical population would go extinct. Dramatic shifts in the structure of entire biological communities may result from the dynamics within the cannibal population. Acts of cannibalism can incur significant costs, most notably risk of retaliation by the intended victim and risk of acquiring parasites and diseases from infected conspecifics. The cost of evolutionary fitness will depend upon the degree of genetic relatedness between cannibal and victim. Cannibals may be morphologically distinct from noncannibals of the same species, as occurs in some lower eukaryotes and larval amphibians.

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