POPULATION BIOLOGY OF MARINE IGUANAS (AMBLYRHYNCHUS-CRISTATUS) .3. FACTORS AFFECTING SURVIVAL

A logistic model was used to identify factors that determined marine iguana survival on Santa Fe, Galapagos between 1981-1987. Body condition was an important determinant of survival when food supply decreased during the 1982-83 El Nino-Southern Oscillation event, and 1983 survival was related to body condition 1 or 2 yr earlier. Mean monthly sea-surface temperature was partly correlated with body condition and there was a significant interaction between the two so that condition was more important at high sea temperatures. Adult males suffered higher mortality but, controlling for size, females had a lower probability of survival. There were differences in probability of survival according to location along the 2 km coastline. Adult population density had a small but significant effect on adult survival, but there was a greater effect of juvenile population density on juvenile survival, indicating competition for food within gross size-classes. Hatchling survival was difficult to model: there were small but inconsistent effects of emergence date, but much of the early mortality was due to predation and most of it is probably independent of size and weight. Year of emergence had a significant effect on survival. -from Authors