Adaptive Strategies and Energetics of Tail Autonomy in Lizards

Abstract

Various methods were used to study and qualify components of tail autotomy adaptation in four species of lizards; Coleonyx var eiegatus (Gekoniadae), Eumeces skiltonianus and Eumeces gilberti (Scincidae), and Gerrhomotus multicar inatus (Aguidae). High frequency of tail breaks in natural population of these species (65%, 62%, 52%, and 74% respectively) suggests the effectiveness of autotomy for predator escape. In species where tail autotomy is most important for escape, regenerated tails are as large or larger than the original tails. Regenerated tails were higher in lipids and energy than original tails, which were, in turn, higher than bodies. The species with alternate uses for the tail (other than predator escape via autotomy) exhibited lower rates of energy allocation to regeneration and the regenerated tails were lower in energy content (both per unit weight and total, proportionately) than tails of other species studied. Total growth energy allocated to tail regeneration varied from 24.7% in G. multicarinatus (the species least adapted for autotomy) to 56.5% in E. gilberti (a species highly adapted for autotomy). Regeneration was most rapid in short—lived early—maturing species, those with several breeding opportunities in a given season. Species with high probabilities of future reproductions (long—lived, late—maturing) and short, seasonally restricted breeding seasons, regenerated tails at low rates. Energy allocations to tail regeneration were varied within and among species. Generally, immatures of all species except G. multicarinatus allocated proportionately less to tail regeneration and more to body growth than adults. Energy allocations to tail regeneration in G. multicarnatus were relatively consistent across age groups. A summary of pathways by which autotomy adaptations may be selected for, or by which retention adaptations may evolve, is presented.