Imps of Darkness

“The iguanas are small, and of a sooty black, which, if possible, heightens their native ugliness. Indeed, so disgusting is their appearance, that no one on board could be prevailed upon to take them as food.”

—Captain James Colnett
of the British Royal Navy, 1798

Grooved teeth act like rakes to scrape algae off rocks.

Black scales absorb heat.

Sharp claws help with climbing and holding on to rocks in strong currents.

A short, square snout makes eating easier.

While the iguana swims, its back spines balance its body.

Partially webbed feet help it swim.

Marine iguanas left a lasting impression on some of the islands’ earliest visitors. When explorer and naturalist Charles Darwin first set eyes on them a decade or more after Captain Colnett, he, too, found them unappealing. He described them as “imps of darkness.” Marine iguanas may look awkward on land, but they rule the water. They dive to great depths to graze on beds of algae, like cows grazing on a pasture.

These are the only lizards in the world with the ability to live and forage at sea. They are endemic to the Galápagos Islands. There are six slightly different species, each from a different island. Scientists believe that they descended from land iguanas that floated out to the islands from the continent on logs or clumps of vegetation. To survive, they had to adapt. Over time, their bodies changed.

Salty Sneezes

Because they swallow seawater with their food, marine iguanas need to get rid of salt from their systems. The salt gets filtered from their blood and then excreted by special glands in their noses. The salt leaves their bodies when they projectile sneeze!

Heat‑Seeking Lizard

Marine iguanas cannot regulate their body temperatures. They must rely on an external source, like the sun, to do it for them. If you read last month’s edition of Explorer magazine, you’ll know what the word for this is: ectotherm—a cold‑blooded animal. Marine iguanas will lose an average of 10 degrees of heat in the cold water. So, before they dive in, they try to soak up enough heat to raise their body temperatures.