The marine iguana (Amblyrhynchus cristatus) live only on the volcanic Galapagos islands off the coast of South America. These large lizards have adapted to island life by learning to swim in the ocean and dive for their food, the only lizards on earth to do so. They’re able to stay underwater a surprisingly long time, allowing them a chance to eat enough food to make the dive worthwhile.
Many marine iguanas are largely black, which helps them absorb heat from the sun and bring up their body temperature more quickly after spending time in the cold ocean water. However, colors can vary by their native island. They also have short, blunt snouts that make it easier for them to eat algae and seaweed from rocks, and they have long, flat tails designed for efficient swimming. Since marine iguanas swallow a great deal of salt as they feed, each of these animals also has a salt gland in his head that removes excess salt from the body.
Swimming and Diving Habits
Most often it is only the large males that make deep dives into the ocean in search of food, sometimes going as deep as 50 feet. The females, and young and smaller males don’t have the body mass to tolerate the cold conditions of a dive, and they are more likely to remain in shallow water, eating from rocks at low tide or seeking out food just below the surface in a series of shallow dives.
Marine iguanas spend most of their lives on the land and do not actually live in the water for any length of time. They breed, nest and sleep on land but enter the ocean when it’s time to eat, seeking out the nutritious plants clinging to underwater rocks. At times the iguanas will only stay submerged for a few minutes, but they have been known to stay underwater for periods as long as an hour before resurfacing to breathe, according to NYU Steinhardt website.
In Times of Hunger
Although marine iguanas can wade or dive into the ocean to eat where the food is more plentiful than on land, it sometimes happens that they’re unable to seek out food due to storms or other adverse conditions. When marine iguanas don’t get enough to eat, they shrink. They lose body mass like most animals do when food is scarce, but these big lizards also get shorter, losing up to 20 percent of their overall length. When food becomes available once more marine iguanas are able to grow back to their former length.
- Galapagos Conservation Trust: Galapagos Marine Iguanas
- Galapagos Conservancy: Iguanas and Lizards
- Gosnell School of Life Sciences: Robert Rothman: Marine Iguana
- New York University: Galapagos Islands: Marine Iguana
- San Diego Zoo Reptiles: Iguana
- San Francisco State University Department of Geography: The Biogeography of Marine Iguana