The Differential Effect of Tail Autotomy on Sprint Performance between the Sexes in the LizardUta stansburiana

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Autotomy of an appendage, especially the tail in lizards, can aid in escape from predators, but that assistance comes with associated costs. In previous studies, decreases in sprint performance often followed tail loss in lizards, and potential sexual differences following tail autotomy can provide evidence for the possible influence of sexual selection on performance in lizards. We measured the impact of tail autotomy on sprint performance in the lizard Uta stansburiana, a species that has frequent natural tail loss. Sprint performance was measured using both maximal sprint speed and average stride length. We examined the impacts separately for each sex, as this species is molded strongly by sexual selection, and tail autotomy is known to affect the social status of male and female subadult U. stansburiana differently. To check for sexual differences in sprint performance, we assessed both sexes with intact tails. Neither sprint speed nor stride length significantly differed between the sexes. Following tail loss, male performance was not affected; individuals maintained their previous maximal sprint speed and average stride length. However, females significantly decreased both maximal sprint speed and average stride length following tail autotomy. We suggest that tailless males maintain high speeds to escape predators because of greater conspicuousness due to sexual dimorphism and behavior, as well as for repulsion of rivals from their territories. Postautotomy females may adopt an alternate social role that does not require their prior sprint speeds. Sexual selection may have advanced this sexual difference in sprint performance after tail autotomy.

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