Virtual Galápagos: Wildlife

Wildlife - Coastal Zone - Marine Iguanas

Introduction

Intertidal Life

Sea Turtles

Land Iguanas

Marine Iguanas

Sea Lions

Fur Seals

Birds

"The rocks on the coast abounded with great black lizards, between three and four feet long... It is extremely common on all the islands throughout the group, and lives exclusively on the rocky sea-beaches, being never found, at least I never saw one, even ten yards in-shore. It is a hideous-looking creature, of a dirty black colour, stupid, and sluggish in its movements."

Charles Darwin,
Voyage of the Beagle

There are probably more marine iguanas on the islands of the Galápagos than any other single creature -- perhaps between 200,000 and 300,000 in all, with a concentration up to 4,500 individuals per mile of coast. While one does get used to their "hideous" appearance, one is never entirely free of a sense of unease. Some say they look like guardians of Hell, or condemned spirits, or dragon spawn; but biologists take comfort in the fact that the Marine iguana (Amblyrhynchus cristatus) is the only sea-going lizard in the world, and is thus of tremendous interest.

Ranging in length from about 10 inches to two feet, these iguanas are usually black or soot-gray, though local populations are sometimes more colorful -- on Santa Cruz, Isabela and Fernandina, the adult males often have green and red blotches as well. Their diet is almost entirely marine algae, which they find both underwater and at the tidal zone, though they sometimes "revert" to their ancestral scavenger's diet of grasshoppers, crustaceans and opportunistic meals such as sea lion afterbirth.

Marine iguanas usually feed only once a day, the mature lizards swimming out through the tidepools to dive to the bottom for algae; smaller iguanas feed off the rocks in the tidal zone. An iguana can loose up to 10 degrees C of body temperature on these feeding missions; being a cold-blooded creature ("ectothermic") , iguanas must bask on the hot lava rocks throughout the day until they regain their internal warmth.