The endemic marine iguanas are excellent living examples of evolution and adaptation on the Galapagos Islands. One of the most interesting adaptations of these creatures is the way they preserve their heat. Their black coloration helps them to absorb the energy of the sun. In addition like other reptiles, marine iguanas are ectothermic. Ectothermic means that these reptiles must regulate their body temperature by physiological and behavioral means.
In the picture of today we can see how the marine iguanas conserve the heat by congregating under vegetation. Today after sunrise, the morning was a little cool for them. To be able to move or swim they must have a high body temperature (35 - 37 °C). Later in the morning when the sun was strong they easily reached their optimum body temperature. We saw many of them swimming offshore into the cold waters heading towards their feeding grounds looking for marine algae. Specially adapted to retain heat, the marine iguanas immediately lower their heartbeat (bradycardia) to about half, lessening the contact of warm blood to their cold exterior.
