Sexual Cannibalism: Blood LustBiology 342 Fall 2012by Ben Goggin and Kata Martin |
|||||||
|
|||||||
Adaptation: The question of ‘adaptive value’ or ‘function’ describes what value the behavior contributes to the animals overall fitness, explaining how the behavior was preserved through time.Numerous hypotheses for the adaptive value have been posed and studied by biologists interested in manifestations of sexual cannibalism in different species, primarily arthropods. The proposed adaptive value of these behaviors depends on the time at which the cannibalistic behavior (by females) occurs relative to fertilization, with pre-copulatory cannibalism benefitting the female and post-copulatory cannibalism potentially benefitting both sexes.The precopulatory cannibalization of males may occur in mating provides no possible reproductive advantages to the male involved, as he loses the specific reproductive opportunity and the potential for any reproductive success to follow. For females, multiple explanations of the adaptive value of this early cannibalization have been researched. Precopulatory sexual cannibalism was suggested to act as a form of sexual selection, demonstrated by studies of the behavior in garden s Post-copulatory cannibalism by females has been suggested to offer adaptive value (in terms of increased reproductive success) to both participating mates. Comparison among species with varying rates of male lifetime matings and varying nutritional strains imposed by mating and gamete production, indicates a model where the occurrence of sexual cannibalism increases as males tend to have fewer matings in their lifetimes and as the costs of each mating increase (Buskirk et al 1984). This indicates the increased reproductive success of sexual cannibalism under these favorable conditions. In orb-web spider (Argiope brownish), the adaptiveness of cannibalism by females was illustrated in a study that measured the offspring survival times of cannibalistic females when they were allowed to cannibalize their mates and when they were prevented from doing so. The females engaging in the cannibalistic behavior showed offspring with increased survival times (and healthier broods), indicating the lifetime fitness gains for both mother and father of offspring resulting from matings where sexual cannibalism occurred (Welke & Schneider 2012).
|