AN EXPERIMENTAL-STUDY OF THE TRADE-OFFS BETWEEN AGE AND SIZE AT MATURITY - EFFECTS OF ENERGY AVAILABILITY

1. We examined the effect of differential energy input on age at first reproduction in an oviparous snake, Elaphe guttata, to address two questions: (i) Does changing energy input in neonates result in changes in size or age at maturity, or are these traits fixed? and (ii) How do the resulting differences in age or size at reproduction (if any) translate into long-term effects on fecundity? 2. We found that individuals on a low-energy diet grew more slowly, matured at a later age, and had smaller clutch sizes than did females on a high-energy diet. However, not all individuals on the high-energy diet matured at the same time. Thirty per cent of these latter individuals matured at 20 months of age at a relatively small body size, whereas the remainder matured at 32 months of age and at a larger body size. 3. In terms of lifetime reproductive potential, early-breeding individuals maintain a higher cumulative reproductive output until 58 months of age; after that point, delayed breeding individuals have a higher cumulative potential.