Characterization of Mechanisms Influencing Cannibalism Among Larval Amphibians
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Cannibalism is a seemingly aberrant interaction, appearing counter to the fitness of individuals. Yet cannibalism is not overly uncommon, and naturally occurs among aquatic organisms, including larval amphibians. In temporary wetlands larval amphibians are in a race to complete metamorphosis before their aquatic habitat disappears. When intraspecific competition intensifies, eating conspecifics may represent a beneficial if not necessary strategy. The research presented within this thesis aims to characterize factors that influence cannibalism within populations of larval amphibians. Wood frog tadpoles (Lithobates sylvaticus) were used to test potential benefits of cannibalism as a diet, determine if dietary quality and nutritional stress influence cannibalism, and investigate the roles of competition and chemical cues in influencing cannibalism. Larval long-toed salamanders (Ambystoma macrodactylum), and ringed salamanders (A. annulatum) were used to investigate a functional link between trophic polymorphism and cannibalism in natural populations. Results suggest that perceived increases in competition may stimulate some individuals to become less risk averse, and more aggressive, which may in turn facilitate cannibalistic behaviour. Cannibalism itself provided only conditional benefits to larval wood frogs, rather than the optimal growth that would be expected from an ideal diet. However, this may have been the result of individual variation in response to the diet and/or conspecific cues as opposed to a nutritional deficit. In conditions where tadpoles could perceive increased competition they altered their behaviour and morphology in ways that may improve their foraging success and potentially promote cannibalism. Finally, a functional link appears to exist between head morphology and cannibalism in natural wetlands. However, the appearance of this morphology appears related to conditions that may facilitate increased population densities through rapid pond drying.
DegreeDoctor of Philosophy (Ph.D.)
SupervisorChivers, Douglas P.; Hobson, Keith A.
CommitteeFerrari, Maud C.; Johnstone, Jill F.; Morrissey, Christy A.
Copyright DateOctober 2015