Galapagos Marine Iguana 

The Galapagos (say gall-app-uh-pug-uss) Islands are located near Ecuador, South America. They are home to some unique animals found nowhere else in the world. They are home to the marine iguana, the only sea-going lizard.

Marine iguanas are found all through the Galapagos Islands. Although the iguanas on each island look a little different and are different in size, they are all the same kind of iguana. The iguanas develop their colours as they get older - the young are black, while adults can be combinations of black, green, red or grey, depending on the island on which they live.The iguanas on the island of Espanola are the most colourful, with blotches of red and green. The red colour comes from a kind of seaweed that blooms in the summer.

Marine iguanas are vegetarians, feeding on seaweed on the rocks, in tidal pools or in the sea. The biggest iguanas, generally males, swim out past the waves and feed underwater. They dive about 1.5 - 5 m down, but some very large adults can dive about 15 m or more. Iguanas are generally underwater for just a few minutes, but have been known to be underwater for over half an hour.

All iguanas are good swimmers, but the marine iguanas are even more so. They swim by moving their bodies from side to side, with their legs held to their sides. Their flattened tails are perfect for swimming. Their claws are longer and sharper than those of land iguanas, so they can cling tightly to rocks along the shore without being pulled away by the waves. Marine iguanas have a blunt nose, which makes it easier for them to scrape algae off the rocks with their sharp teeth.

Iguanas are reptiles, and therefore cold blooded. This means they need outside heat to warm their bodies. In an animal that dives into the sea, this is a bit of a problem. Marine iguanas have the same features as other diving animals: when they dive, their blood moves away from the surface to save body heat, and their heart beat slows down drastically. Only the largest males dive because larger animals lose less body heat.

In the Galapagos Islands, the rocks at the edge of the sea are black volcanic rocks. When they come out of the sea, marine iguanas bask on these rocks, which attract heat because of their dark colour. At night, marine iguanas huddle together to keep warm. In the hottest part of the day, iguanas will lift their faces to the sun, which presents the narrowest part of their bodies to the heat and allows a breeze to cool their bodies. If it is very hot, they will find cracks or holes to shelter in.

While they feed in the sea, marine iguanas swallow a lot of salt water. They have special glands between their eyes and nostrils that collect and remove salt. The salt gathers in the nostril, and the iguanas sneeze it out periodically. The salt spray then shoots up in the air and often falls back onto the marine iguana's head, looking a bit like a white wig.

Marine Iguanas live in large colonies for most of the year. In the breeding season, usually December and January, they become territorial. Males establish and maintain territories in the dry places above the water line, and near the nesting groungs. Males fighting begins with a head bobbing display, with their mouths wide open. After a while the males charge each other, locking heads using the triangular crests on the top of their heads, and then pshing and shoving. The fights can last for up to 5 hours. Once he has won his territory, a male waits to attract a female to his territory, and then mating takes place. The females then leave, and about 5 weeks later they lay their eggs in a soft, sandy spot. They dig the nest by pushing the dirt back with their front legs, then out with their hind legs. During nesting, the females are aggressive towards each another, and will guard their nests for some time after laying.

Another amazing feature in marine iguanas is that when there is not much food around, they don't just become thinner, they get shorter too. It has been discovered that marine iguanas shrink in length and then regrow when food becomes plentiful again. Part of their backbone shrinks. Adult iguanas can switch between growth and shrinkage repeatedly throughout their lifetime.

Galapagos Marine Iguanas are classified as vulnerable. In 1982 and 1983, water temperatures were higher and other kinds of algae grew and prevented growth of the algae that iguanas normally feed on. Many iguanas died of starvation. Introduced animals such as rats, pigs, cats and dogs have killed the young in many breeding colonies. Oil spills and other marine pollution are serious threats to marine iguanas, especially because they live in such a small area.

The government of Ecuador has made laws to protect the marine iguanas. Artificial nesting sites have been set up on smaller islands away from predators because it is too difficult and would take too long to get rid of the predators on the islands where they have been introduced.

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updated May 2003