Reproductive trade-offs in Caiman crocodilus crocodilus and Caiman crocodilus yacare: Implications for size-related management quotas

Abstract

Management strategies for crocodilians often include size-selective quotas designed to protect breeding females. However, little is known about among- and within-population variation in size and fecundity in crocodilians. Life-history theory predicts trade-offs between clutch size and egg size. Larger females usually have larger clutch sizes, and if they also produce larger eggs their contribution to reproductive effort may be greater than the number of eggs they produce. We studied the relationships among female size and clutch characteristics for an Amazonian population of Caiman crocodilus crocodilus between 2001 and 2007, and a Pantanal population of Caiman crocodilus yacare in 1996. Females in the Amazonian population were smaller, and showed significant differences from the Pantanal population for some relationships. Eggs lost weight during incubation in the Amazonian population but not in the Pantanal population. Despite these differences, the effect of egg size accounted for about one quarter of the total effect of female mass on clutch mass in both populations. Size-selective quotas should take into account that large females produce both more and larger eggs than do small females. However, size distributions of breeding females vary greatly among populations and legal size limits will be more effective if based on data from local populations.