Foraging strategies of the Galapagos marine iguana (Amblyrhynchus cristatus): adapting behavioral rules to ontogenetic size change
Behaviour
1994
Journal Article
128
3/4
255-279
Amblyrhynchus cristatus
Ontogenetic development in reptiles entails major changes in size-related foraging options. We studied the changes in foraging behavior of marine iguanas. In this species, size increases about twenty-to hundredfold from hatching to full adult size. The foraging strategy of marine iguanas was studied at Miedo on Santa Fe Island in the Galapagos archipelago. During low tide, large marine iguanas (>250 mm snout vent length (SVL)) foraged more in the lower intertidal than small ones (<250 mm SVL) which preferred the upper intertidal with higher temperatures and less frequent wave washing. Animals usually returned to the same foraging site day after day and had lower food intake after changing their foraging site. Feeding accounted for 60% of the time spent in the intertidal. Smaller animals fed every day, larger ones only every other day. Smaller individuals shuttled faster between foraging and basking sites than larger ones. Total feeding time per day was, however, the same for both size classes. At neap tides (= high water level at low tide) animals had shorter foraging bouts than at spring tides with much lower water levels at peak low tide. Length of feeding bouts depended most on wave action, time of low tide (during the daylight period), and body mass of an animal. Small animals fed significantly less at higher than at lower wave activities. All animals on Santa Fe spent more time feeding.