Document Type

Honors Thesis


Cannibalism, a behavior in which an organism preys on conspecific individuals, has contrasting fitness effects at the population level and the individual level. Cannibalism reduces the population fitness by directly eliminating individuals but may increase individual fitness by increasing nutrition and reducing competition for resources such as food and mates. While cannibalism provides both costs and benefits to fitness, predation of other species is predicted to be a better feeding strategy as it does not carry the population level fitness cost. Here, we seek to compare the cannibalism rate between Gnatocerus cornutus and Tribolium castaneum, two flour beetle species that differ in the role of male-male competition for mates. For our experiment, adult beetles of each species were separated by sex and provided with conspecific and heterospecific pupae as prey. We measured cannibalism rate as the difference between the number of conspecific and heterospecific pupae eaten. Our results indicate a significant interaction between predator species and sex on cannibalism rate, with G. cornutus males being most cannibalistic while T. castaneum males are least cannibalistic. Our findings suggest that in species with strong competition among males, high rates of cannibalism may evolve because the individual fitness gains outweigh the fitness cost to the population.

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