“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.”
Colnett of the British Royal Navy,1798
Grooved teeth act like rakes. They scrape algae off rocks.
Black scales absorb heat.
Sharp claws help with climbing and holding on to rocks in strong currents.
A short, square snoutmakes eating easier.
While the iguana swims, back spines balance its body.
Partially webbed feet help it swim.
Marine iguanas made a big impact on some of the islands’ earliest visitors. When naturalist Charles Darwin first set eyes on them years after Captain Colnett, he found them unappealing as well. 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.
These are the only lizards in the world that can live and forage at sea. They are endemic to the Galápagos Islands. Scientists believe that they are descended from land iguanas that floated out to the islands from the continent on logs or vegetation.
Marine iguanas swallow seawater with their food. Then they need to get rid of salt from their systems. The salt gets filtered from their blood. It is then excreted by special glands in their noses. The salt leaves their bodies when they sneeze!
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.