We’re on St. James Island in the Galapagos Islands off the coast of Ecuador. It was here, in 1835, that the young Charles Darwin came as a naturalist aboard the ship Beagle and noticed that characteristics of certain animals seem to vary from island to island. It’s a discovery that laid the foundation for his ground breaking study of evolution, The Origin of Species. I’m Jim Metzner, and this is the Pulse of the Planet, presented by the American Museum of Natural History.
One of the animals that has adapted for life on the Galapagos Islands is the Marine iguana. Scientists speculate that these reptiles descended from land iguanas which floated over on driftwood rafts from South America. Over time, the Galapagos iguanas took to the ocean, developing the ability to swim long distances, and feed off algae from ocean rocks.
“When they’re swimming, you’ll see them fold their arms to the sides, and only use their tail, which is longer than the body itself, and flat, so they could swim with snake movements in the water.”
Ivonne Torres is a naturalist and guide on the Galapagos Islands.
“They’re very powerful; they can dive down and hold on to the rocks to feed off the algae.”
But in order to feed off ocean algae, the iguanas must be able to stay underwater for long periods of time. And although they haven’t evolved gills to replace their lungs- they have found a way to use their oxygen more efficiently.
“They shut off blood vessels, allowing the blood only to circulate in vital parts of the bodies where they need the oxygen. Also they lower their heart rate to only four heart beats a minute. With this method, they’re able to stay underwater for at least one hour.”
Additional funding for Pulse of the Planet has been provided by the National Science Foundation. I’m Jim Metzner.