The Galapagos are home to two families of iguana, one land-based and the other seagoing. They share a common ancestor but over millions of years have adopted very different coloring and behaviors in response to their very different daily environments. While the two species still live within yards of each other the individuals rarely cross paths any more.
The land iguana has developed a light yellow color to shed as much heat as possible in the equatorial sun.
We saw all our land iguanas on the first hike of the trip, Dragon Hill on Santa Cruz island. Hernan was our guide for this landing.
Land iguana eyesight: not so hot
The land iguanas live for the cactus flower and have developed a high sensitivity to the colors yellow and white. That’s about the extent of their visual acuity, as anything yellow or white apparently registers as food with these beasts.
There was a minute of frozen panic as the iguana crept closer to taste one hiker’s white running shoes.
Unimpressed with the taste of shoe leather our reptile buddy paused, slowly deciding whether or not it was time to slink back to cover. Using a forked twig, Hernan silently twisted a flower loose from a nearby catcus. With an advanced sense of hearing to compensate for their lousy vision, these iguanas can hear a cactus flower hit the dirt a mile away.
Hernan quietly explained what happened next: to clean the little spikes off the bloom the iguana dug a tiny pit and rolled the flower around in the dust, rubbing the thorns off prior to chowing down.
These are the only aquatic iguanas in the world, diving for up to an hour to scour algae and seaweed from the rocks. They’ve developed a dark coloring to maximize heat generation in the weak sun down below.
To metabolize all that salt back out of their systems they come equipped with excretory glands near their eyes, and sneeze the salt out their nostrils back on land. It’s pretty entertaining to watch an iguana take one step, nod its head and snort salt – over and over across the rocky shore.
They’re social animals, piling up by the hundreds to stay warm at night.