SEXUAL DIMORPHISM IN THE EASE OF TAIL AUTOTOMY - UTA STANSBURIANA WITH AND WITHOUT PREVIOUS TAIL LOSS

Tail autotomy is used by many lizard species to escape predation, but in those species that have the adaptation, the degree to which it is d eveloped depends on relative costs and benefits. The same may be true for the development of tail autotomy in the two sexes of the same spec ies. We examined the ease of tail autotomy of male and female Uta stan sburiana. Correcting for tail thickness, males lose their tail signifi cantly less easily than females and retain it even more strongly as th ey grow larger from sexual maturity on. Although both sexes lose socia l status after tail loss, females may have available an alternative, s ubordinate, social role in which they can retain some reproductive suc cess. Males do not have such an alternative strategy, and since they n eed both a complete tail and high social status for reproductive succe ss, they require more stimulus to autotomize their tail (i.e., the cos t of tail autotomy is higher in males than in females). For both males and females,lizards with incomplete tails from a previous autotomy ha ve reduced antipredator defense via tail autotomy, We predicted that s econd-time autotomy would occur more readily as compensation. But fema les did not show this compensation and autotomized the tail with equal ease the first and second times, Males autotomized more easily the se cond time, but we do not interpret this change as compensation for a s horter tail. For males, the cost of tail loss is much reduced after a prior tail autotomy they have already lost their social status followi ng autotomy, and further tail loss Is less consequential. At the secon d autotomy, males reduced their ease of tail autotomy to equal that of females, and females did not show facilitated second time autotomy, T herefore, males, like females, did not show easier tail autotomy as co mpensation for an incomplete tail.