Abstract
Abstract Organisms require energy for survival, growth, and reproduction. In a system with a finite energy supply, fluctuations in resource availability can select for plasticity in the allocation of resources between competing physiological processes. Infrequently-feeding snakes, which naturally experience extended episodes of fasting, have evolved the capacity to modulate gastrointestinal (GI) performance in response to changes in digestive load. Specifically, the gut can be downregulated during fasting to reduce metabolic maintenance costs. Some energy is, however, required to upregulate the digestive system again to allow the exploitation of captured prey. Despite significant inquiry into the relationship between sit-and-wait foraging tactics and GI plasticity, quantitative examination of the optimal digestive strategy for an infrequently-feeding snake is lacking. Here, we construct an optimisation model to quantitatively predict this strategy in terms of the length of time post-feeding after which gut downregulation occurs and the minimum prey mass required to initiate gut upregulation. Contrary to long-held assertions, our simulations predict that infrequently-feeding snakes of all sizes that practice gut downregulation benefit from consuming relatively small prey. We identify gut downregulation as an adaptive strategy when prey are small and encountered infrequently, and assert it as a critical factor in determining predator vulnerability to food scarcity. When parameterising the model, we found the distribution of potential prey body sizes to be poorly characterised in the literature. Accordingly, we identify the frequency distribution of individual body sizes within a terrestrial community as a key focus of future ecological research.
Published Version
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