Sexual Cannibalism: The Possible Models
Sexual cannibalism occurs within many species of the arachnid family. The adaptive value of this development, and whether such value exists, is a major question. Four major models have been proposed to explain the evolution and adaptation of sexual cannibalism. This cite explores these hypothesis through Niko Tinbergen's Four Questions : Phylogeny, Ontogeny, Adaptive Value, and Mechanism. Each category of development is adressed within the four models.
Silk spider eating its conspecific.
Image courtesy of wikipedia.org
Theory 1: Economic Model
This theory suggests that there is an adaptive value for cannibalism only when the female has a large number of opportunities to mate and has few other prey options. When prey is scarce and the female is hungry, she will eat potential mates before copulation. This shows that the occurrence and furthermore the evolution of cannibalistic behavior may be the result of environmental cues.
Theory 2: Life History
This model proposes foraging vigor, an effect of the female’s life-history and development, to be the causation of sexual cannibalism. Maturing at a smaller size, with less avaliable food, females increase their aggression and cannibalistic behavior.
Theory 3: Male Complicity
Sexual cannibilism is an extreme case of parental investment on behalf of the male. Accordning to this model, cannibalism by his mate increases the number and fitness of the male's progeny. This model suggests that when the male is cannibalized by the female, more of her offspring will inherit his genes and will be more likely to survive.
Theory 4: Female Choice
This model proposes the timing of cannibalization may act as cryptic choice, and therefore female spiders control paternity (Elgar et. Al. 2000). The female may delay cannibalization, and with prolonged copulation, the male fertilizes more eggs.