TALES OF LIZARD TAILS - EFFECTS OF TAIL AUTOTOMY ON SUBSEQUENT SURVIVAL AND GROWTH OF FREE-RANGING HATCHLING UTA-STANSBURIANA

Potential costs and benefits of tail autotomy in lizards have been inf erred almost exclusively from experimental study in semi-natural enclo sures and from indirect comparative evidence from natural populations. We present complementary evidence of the costs of tail autotomy to th e lizard Uta stansburiana from detailed demographic study of a natural population. On initial capture, we broke the tails of a large sample of free-ranging hatchlings (560) and left the tails of another large s ample (455) intact, and then followed subsequent hatchling growth and survival over a 3-year period. Surprisingly, in 1 out of the 3 years o f study, survival of female hatchlings with broken tails exceeded that of female hatchlings with intact tails. Furthermore, no effects of ta il loss on survivorship were detected for male hatchlings. However, in 2 years when recaptures were very frequent (1961, 1962), growth rates of hatchlings with broken tails were significantly slower than those of their counterparts with intact tails. We discuss our results in the broader context of estimating the relative costs and benefits of tail autotomy in natural populations. and suggest that long-term demograph ic studies will provide the best opportunity to assess realized fitnes s costs and benefits with minimum bias. We also describe how experimen tally induced tail autotomy can be used as a technique to complement e xperimental manipulation of reproductive investment in the study of li fe-history trade-offs.