Galapagos iguana is a general term used to describe a few types of iguanas that inhabit the Galapagos Islands, a group of volcanic islands off the coast of Ecuador. There are believed to be four types of iguanas that occupy these islands. They are split into three loose categories, which are land iguanas, marine iguanas, and hybrid iguanas. The three species of Galapagos iguanas that live on land are Conolophus subcristatus, Conolophus pallidus, and Conolophus marthae, while the the Galapagos marine iguana is known scientifically as Amblyrhynchus cristatus. A hybrid, or cross-bred version of these two types of lizards is primarily only found on one island in this archipelago.
A Galapagos land iguana can grow to be up to 25 pounds (11.3 kg) and 5 feet (1.5 m) long. The animal has dorsal spikes running from its neck to its tale. Like most other types of lizards, it has an elongated body with four, short, stubby legs protruding from its sides.
These are cold-blooded animals. During the day, they can often be found basking on the dark volcanic rocks, but after the sun sets, they will usually burrow into the dry soil to help preserve their body temperature. Unlike other lizards, however, they are almost predominately herbivores. Their diet consists mainly of native cacti that can be found growing on the islands, which are also the main source of water in this arid climate.
C. subcristatus can be found mostly in the central area of this cluster of islands, and it is typically rust colored on top and has a yellow-orange colored underside. The Barrington land iguana, or C. pallidus, is typically lighter in color and can be found on Santa Fe Island. One relatively newer discovery, C. marthae, or the Galapagos pink land iguana, is a dusky pink color with dark vertical stripes.
First discovered in 1986 by park rangers, the pink Galapagos iguana can be found almost primarily on parts of Isabel Island. In 2009, it was officially recognized as a sub-species of the Galapagos land iguana. It was originally given the scientific name of C. rosada, because rosada means pink. Today, it has been renamed C. marthae, after describer's stillborn daughter.
The Galapagos marine iguana, or Amblyrhynchus cristatus, is considered to be one of the only predominately marine lizards alive today. It lives in the waters of the Pacific Ocean surrounding the Galapagos islands, and can grow to be up to 6 feet (1.8 m) long. Its body is black or dark gray, which helps the animal absorb heat from the sun after long dives in the cold waters. Many times, its snout will appear to be white, but this is just from extra salt that is taken in while eating and expelled through special nasal cavities.
As it lives in the ocean, this Galapagos iguana has a specially adapted body. Its long tail is flat, which allows it to swim easily and dive more than 50 feet (15.2 m). Once it is under the water, the Galapagos marine iguana can stay below for roughly a half hour, often scraping at the rocks with its flat snout and teeth in search of marine algae and seaweed. While it will also use its long, sharp claws for this purpose, they are generally used to hang on to rocks to stop the heavy current from sweeping the creature further out to sea.
On South Plaza Island, the land and sea iguanas have overlapping territories. When a female Galapagos land iguana and a male Galapagos marine iguana breed successfully, their offspring is considered to be a hybrid iguana. This Galapagos iguana is believed to have the best of both worlds. It is able to survive and even thrive, both on land and in the water.
Many scientists believe that the different species of the Galapagos iguana are descended from one common ancestor. In this theory, scientists claim that iguanas floated to these islands from neighboring areas on large clumps of seaweed and algae. Afterward, some stayed living in the ocean, while others ended up on land. Other scientists, however, claim that the marine iguanas are descended from ancient sea reptiles.