Marine Iguanas of the Galápagos

Ecuador’s Galápagos Islands are known for their many unique and interesting animals that live nowhere else in the world. Most people, if asked, would probably mention the Giant Tortoises as being the islands’ most distinctive creatures. Others might mention the many different types of Galápagos Finches that inspired Charles Darwin to formulate the theory of evolution. Then there are the Marine Iguanas, those curious lizards that congregate on rock outcroppings, splashed by breaking waves.

These lizards are neither cute nor colorful – Darwin referred to them as “hideous” and “disgusting clumsy”, and they are mainly black in order to best absorb the heat of the sun. Yes, marine iguanas are lizards and as such, are cold blooded.

This leads one to wonder how marine iguanas can survive at all, being sea-adapted animals that must swim in the cold waters of the Pacific Ocean in order to procure their food. But swim they do, and in fact they can remain underwater searching out and eating food for up to 30 minutes at a time. When they emerge, stiff and sluggish, they make for the aforementioned black lava rock outcroppings, there to bask in the sun and warm up again before diving in for their next meal. And what is it they eat? The answer is, again, a surprise: marine iguanas are vegetarians. They use their razor-sharp front teeth, shaped like little tridents, to scrape algae off of the rocks and coral near the shore. The mechanics of their eating style has, over millions of years, caused their snouts to become progressively shorter and flatter, the better to scrape algae with. Marine iguanas have evolved another adaptation to sea life; salt glands in their noses that extract salt from the large amounts of seawater the creatures ingest while eating underwater. As they bask in the sun, marine iguanas will “sneeze” the salt out of their noses. A good portion of the expelled salt lands on their heads, tinting them a grayish-white color that reminds some of the wigs English judges wear.

Like many Galápagos Islands fauna, marine iguanas have few if any natural predators and have little defense against introduced mammals like dogs, cats and rats. Populations of marine iguanas have shrunk in areas near human habitation but continue to thrive on isolated and uninhabited islands of the Galápagos archipelago, where they are a popular attraction for tourists.