Meet the Only Sea-Faring Lizard: The Marine Iguana

Written By Carly Day

The marine iguana of the Galápagos Islands is definitely not the pretty boy of lizard society, with its multiple neck rolls, stunted nose (part of their genus name—Amblyrhynchus—literally translates to “blunt snout”), and knobby head, but he certainly is a rugged-looking character with some fascinating adaptations to his tough environment.

Though Charles Darwin referred to marine iguanas as “disgusting clumsy lizards” and “imps of darkness,” they are, in fact, the only ocean-going lizard in the world, putting them in the same class as marine reptiles, such as saltwater crocodiles and sea snakes.

Every island of the Galápagos contains its own style or subspecies of iguana—in many different colors, shapes, and sizes. Marine iguanas weigh from 1 kilogram (2.2 lbs) to 12 kilograms (26 lbs). Scientists hypothesize that a few million years ago, land-dwelling iguanas from South America must have fallen asleep on a piece of driftwood and wound up in the Galápagos, spawning generations of bumpy-faced marine iguanas.

In spite of their thug-like exterior, marine iguanas are actually sweet little vegetarians, their herbivorous diet consisting only of seaweed and underwater algae. Those pointy teeth aren’t for tearing flesh, but for scraping algae off rocks, and their long claws are best used for hanging on to rocks as they negotiate strong currents underwater. They can stay submerged for up to one hour and dive as deep as 65 feet (20 m) in search of their greens.

Their dark grey skin helps them warm up quickly by absorbing sunlight after they emerge from the icy seas around the Galápagos Islands. However, the males tend to sport a brighter array of colors—to attract females during the breeding season. And hats off to evolution for creating unique glands to cleanse the extra salt they consume from their blood, excreted by sneezing, leaving their heads encrusted with salty mounds.

These unique lizards are classed as vulnerable under the IUCN Red List of Threatened Species and are thus protected; however, they continue to face threats from predators such as rats and wild cats and dogs, who eat their eggs and young. Climate change also threatens the marine iguana, as sea level and rising temperatures can alter its nesting areas on the beach and its ability to regulate its own body temperature on land.