Sexual Dimorphism in the Ease of Tail Autotomy: Uta stansburiana with and without Previous Tail Loss

Abstract

relative costs and benefits. The same may be true for the development of tail autotomy in the two sexes of the same species. We examined the ease of tail autotomy of male and female Uta stansburiana. Correcting for tail thickness, males lose their tail significantly less easily than females and retain it even more strongly as they grow larger from sexual maturity on. Although both sexes lose social status after tail loss, females may have available an alternative, subordinate, social role in which they can retain some reproductive success. Males do not have such an alternative strategy, and since they need both a complete tail and high social status for reproductive success, they require more stimulus to autotomize their tail (i.e., the cost of tail autotomy is higher in males than in females). For both males and females, lizards with incomplete tails from a previous autotomy have reduced antipredator defense via tail autotomy. We predicted that second-time autotomy would occur more readily, as compensation. But females did not show this compensation and autotomized the tail with equal ease the first and second times. Males autotomized more easily the second time, but we do not interpret this change as compensation for a shorter tail. For males, the cost of tail loss is much reduced after a prior tail autotomy; they have already lost their social status following autotomy, and further tail loss is less consequential. At the second autotomy, males reduced their ease of tail autotomy to equal that of females, and females did not show facilitated second-time autotomy. Therefore, males, like females, did not show easier tail autotomy as compensation for an incomplete tail.