Marine iguana is the only lizard that feeds entirely in the sea. Marine iguanas live on land, on the rocky coastlines of the Galapagos Islands. The Galapagos are a group of islands in the Pacific Ocean about 600 miles (970 kilometers) west of Ecuador.
Marine iguanas are generally grayish-black in color, with a lighter gray face. Some may also develop red or green coloring during the mating season. Male iguanas living on the island of Española, for example, are sometimes called Christmas iguanas because they take on a bright red and green coloring. Dark coloration protects the marine iguana’s skin from sun damage and helps to warm its body by absorbing heat. Marine iguanas are cold-blooded and thus unable to regulate their body temperature directly. Because seawater is cold, marine iguanas must lie in the sun to warm up after swimming.
Marine iguanas swim out into the cold surf to eat seaweed and algae. They are excellent swimmers. A marine iguana moves through the water by swishing its body and flattened tail from side to side. Marine iguanas can stay underwater for more than an hour. However, they usually make only 5- to 10-minute dives close to shore. They can dive to about 65 feet (20 meters). They have a blunt snout, enabling them to scrape seaweed off rocks with their teeth. They use their clawed toes to cling to slippery rocks while they feed.
A marine iguana communicates by raising and lowering the spiny crest along its head and back. It may bob its head to warn predators or other marine iguanas to stay away. Special glands connected to the nose collect salt from seawater while the iguana feeds, helping to keep the iguana’s body from accumulating too much salt. The iguana can then sneeze out the salty water, either to empty the glands or to startle predators. The marine iguana has few natural predators. On land, crabs, hawks, herons, owls, and snakes prey on marine iguanas. The iguana’s eggs and young are especially vulnerable to such invasive predators as rats and feral (wild) cats and dogs.
Marine iguanas can live up to 60 years. They grow about 2 to 5 feet (0.6 to 1.5 meters) in length, varying in size from island to island. The largest iguanas live on the islands Fernandina and Isabela. Smaller ones live on the island Genovesa.
Male marine iguanas occasionally fight each other for mates. Females may fight each other for nesting spots. The female digs a burrow 12 to 31 inches (30 to 79 centimeters) deep about 1,000 feet (300 meters) inland. There, she lays 1 to 6 eggs—usually 2 or 3. The eggs hatch 3 to 4 months later. Females are vulnerable to predators when nesting, and few young survive.
Marine iguanas are threatened by storms and other natural disasters, pollution, and invasive predators. The marine iguana is protected by law in reserves on the Galapagos Islands.
