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Individual snakes can exhibit a diversity of antipredator responses including crypsis, flight, and a variety of stereotyped behavioral reactions to predators at close range. Among these responses are behavioral differences in the movement (e.g., waving or wiggling) of a conspicuous tail by an otherwise cryptically colored snake. Defensive tail displays may disorient a predator, divert attack to the tail, act as a warning signal, or serve no function at all. The use of tail displays in snakes may also depend on current physiological investment into color production and body size, which can affect locomotor ability to escape predators. The purpose of this study was to determine if variation in tail color is related to the defensive tail behavior exhibited in Common Garter Snakes (Thamnophis sirtalis) when subject to a sudden tactile stimulus. We also analyzed potential relationships between tail coloration, mass, and circulating concentrations of testosterone, to determine if conspicuous tail morphology is condition-dependent. Here, relative tail orange coverage is significantly related to defensive tail behavior and also yields significant negative correlations with mass and testosterone concentrations. This suggests conspicuous tail displays in T. sirtalis to be a size-dependent response to predation, as mediated by testosterone. The prevalence of this defensive behavior in relatively smaller snakes may function as a diversion of attack to the tail while larger snakes instead exhibit greater locomotor capacity to escape predation.

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