Tail injuries increase the risk of mortality in free-living lizards (Uta stansburiana).

Caudal autotomy is an effective anti-predator mechanism used by many lizard species. Fitness benefits of surviving a predatory attack are obvious, although lizards that autotomize their tails may be at greater risk during subsequent encounters with predators than lizards with complete tails. In previous laboratory studies, tail-less lizards were more vulnerable to capture by predators, but little is known about the relative survival of tailed versus tail-less lizards in nature. This study reports on significant associations between naturally incurred tail injuries and the subsequent risk of mortality in 7 populations of the lizard Uta stansburiana. I used standard mark-recapture techniques to document survival and quantified tail injuries by estimating tail completeness. I then used sampled randomization tests to compare intitial tail completeness values of surviving versus non-surviving lizards. I evaluated overall patterns by comparising the means of tail completeness values of survivors versus non-survivors among mark-recapture sequences. Lizards with incomplete tails suffered higher mortality in the field, although this was not true for every comparison considered (i.e., for every mark-recapture sequence analyzed), and the overall trend was much stronger for adult males than for either adult females or juveniles. Higher mortality among lizards with incomplete tails is presumably a consequence of increased vulnerability to capture by predators. Vulnerability to predation of tail-injured lizards may be confounded by reduced social status in this species, because social subordination can result in the occupation of an inferior home range.