Effects of foraging mode and season on the energetics of the Marine Iguana, Amblyrhynchus cristatus

1, Marine Iguanas (Amblyrhynchus cristatus) inhabiting the rocky shores of the Galapagos Islands apply two foraging strategies, intertidal and subtida l foraging, in a seasonal climate. Effects of both foraging strategy and se asonality on the daily energy expenditure (DEE) were measured using doubly labelled water. 2, Difference in foraging mode did not result in significant differences in DEE. 3, On Santa FC the DEE in the warm season was significantly higher than in the cool season (57.8 +/- 21.8 kJ kg(-0.8) day(-1) vs 38.0 kJ kg(-0.8) day( -1)). This difference can be explained by body temperature. A model estimat e of the body temperature was used to predict monthly DEE figures, giving a year round budget. On average a l-kg iguana would need only 47 kJ day(-1), or 17 mJ year(-1). This is lower than previous estimates in which body tem peratures were not taken into account. 4, The water flux of the Marine Iguana increases with increasing foraging t ime. The linear rise per minute foraging is roughly two times as high for s ubtidally foraging animals as for intertidal foragers.