The effect of body size and personality on anuran fitness



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Differences between individuals in morphological and behavioral traits result in differential fitness. Here I present the findings of my research which investigates the role of body size and personality (i.e. consistent individual differences in behavior) in anuran fitness. For my first chapter, I construct a cohort- and individual-based allometric population simulation to examine the effect of body size, and control methods that alter body size on the population dynamics of invasive Australian cane toads (Rhinella marina). Model estimates of adult population density were close to field reports from the established populations. Out of our selected control methods (hand removal, meat ants, tadpole alarm chemicals, and a combination of tadpole alarm chemicals and meat ants), the combined application of meat ants and tadpole alarm chemicals had the greatest reduction in adult population estimates. The effect of varying levels of hand removal was non-linear, suggesting that increased hand removal efforts may not be worth the cost. A relative sensitivity analysis conducted on the model revealed that metamorph survival, juvenile survival, and metamorph growth rate had the greatest effect on estimates of adult population density, which supports our finding that control methods that have the greatest effect on metamorph survival will have the greatest effect on population dynamics. In my second chapter, I examine túngara frog (Engystomops pustulosus) tadpoles for consistent individual differences in anti-predatory behaviors in the presence of two simulated predation threats: aquatic and aerial. Tadpole change in activity and latency to resume activity were quantified for each predation threat. All behavioral responses, except for tadpole change in activity in response to simulated aerial predators, which was significantly affected by trial, were highly repeatable. In addition, there was a significant effect of clutch on all quantified behaviors. A significant correlation between personality traits, i.e. a behavioral syndrome, was present between tadpole change in activity in response to a simulated aquatic predator and the latency to resume activity in response to a simulated aerial predator. A positive correlation between these two behaviors indicates that there is a trade-off in the strength of tadpole responses to different predation threats. Overall, the studies presented here reveal the potential role that individual differences in morphology and behavior play in anuran fitness.



Frogs, Anuran, Body size, Predation risk, Tadpole