The effects of tail loss on survival, growth, reproduction, and sex ratio of offspring in the lizard Uta stansburiana in the field

Abstract

Tail autotomy is a defense against predators used by many lizard species but is associated with various costs, most of which have been measured only in the laboratory. We conducted a field experiment in which we induced tail autotomy to approximately half (58%) of a marked sample (n=326) of Uta stansburiana from western Texas in the fall, and left the other half with intact tails. The following spring we determined survival, measured growth, and brought females to the laboratory to allow them to oviposit their eggs, which we incubated until hatching. Based on past studies, we anticipated inferior survival, growth, and reproduction following tail autotomy. We also predicted that females with tail loss would be energetically compromised and would alter the sex ratio of their offspring toward more daughters (as predicted by the Trivers-Willard hypothesis). Tailless lizards experienced significantly reduced survivorship, but those that survived grew the same as their tailed counterparts. Tailed and tailless females produced clutches equivalent in number of eggs and total mass. Whereas tailed females showed a significant positive relationship between average egg mass and snout-vent length, tailless females did not. Contrary to our expectations, tailless females produced heavier hatchlings than tailed ones, and sex ratios of hatchlings were equivalent for tailed and tailless females. In this population, tail loss in subadults leads to an increased risk of death, but apparently does not impose an energetic handicap such that later growth and reproduction suffer. We suggest that because tailless females are faced with decreased reproductive value, they respond by growing as much and laying as many eggs of the same mass as tailed females, despite the fact that they are also regenerating the tail. In addition, they somehow produce larger hatchlings than tailed females. Nevertheless, tailless females probably end up with lower overall lifetime fitness than tailed females, and tail loss thus induces the conditional reproductive strategy "make the best of a bad situation". Because tailless females produce larger, not smaller, hatchlings, they do not produce more daughters as predicted; i.e., we found no evidence for the Trivers-Willard effect following tail autotomy.

Terminal Investment Induced by Immune Challenge and Fitness Traits Associated With Major Histocompatibility Complex in the House Sparrow

“…Beyond age, extrinsic mortality factors can produce the same shift in allocation rule between life-history traits. These factors include physical damage (Geller 1990;Candolin 1999;Fox and McCoy 2000), food availability (Reznick and Bryga 1987), temperature (Kight et al 2000), social structure (Harvell and Grossberg 1988), and the presence of predators (Crowl and Covich 1990;Reznick et al 1990) and pathogens (Minchella and LoVerde 1981;Lafferty 1993;Polak and Starmer 1998;Adamo 1999). In this study we show, to the best of our knowledge for the first time, that simulated infections by means of injections with an inert antigen is a sufficient cue to produce an alteration in patterns of reproductive investment in a natural population of house sparrows.…”

Senescent birds redouble reproductive effort when ill: confirmation of the terminal investment hypothesis

“…Fox & McCoy 2000;Bonneaud et al 2004;Javois & Tammaru 2004) and decreasing in others (e.g. Ilmonen et al 2000;Råberg et al 2000;Bonneaud et al 2003).…”

Tail loss and narrow surfaces decrease locomotor stability in the arboreal green anole lizard (Anolis carolinensis)

“…For example, tail autotomy may lead to decreased shortor long-term survival (Fox and McCoy, 2000) as a result of decreased running performance (Martin and Avery, 1998), changes to escape behavior (Downes and Shine, 2001), increased energetic costs to regenerate the tail (Naya et al, 2007), and decreased reproductive fitness (Dial and Fitzpatrick, 1981). Yet even some of these findings may be contradictory (e.g.…”