Iguana, Galápagos land

Conolophus subcristatus

phylum: Chordata

class: Reptilia

order: Sauria

family: Iguanidae

status: Vulnerable, IUCN

range: Ecuador (Galápagos Islands)

Description and biology

The Galápagos land iguana is a large iguana with a stout body. It has well-developed limbs, a moderately long tail, a large head with prominent jaw muscles, and a spiny crest running along its back. The largest land iguanas reach a length of almost 4 feet (1.2 meters). Males, which are always at least twice as heavy as females, weigh an average of about 15.4 pounds (7 kilograms). This iguana is yellowish-brown in color with patches of black, brown, and rust.

Like other large iguanas, the Galápagos land iguana is primarily a vegetarian. It eats low-ground plants and shrubs, as well as the fallen fruit and pads, or leaves, of cactus trees. These succulent pads provide the iguana with most of the moisture it needs during dry periods. During the midday heat, iguanas seek out the shade provided by cactus trees or other

vegetation. At night, to conserve heat, they sleep in burrows they have dug in the ground.

Male land iguanas are very territorial and often aggressive toward one another. They patrol the boundaries of their territories and deter intruders with various displays, including rapid head nodding. More than one female usually inhabits the territory of a single male. In July, a few weeks after mating, a female land iguana lays 7 to 25 eggs in a burrow she has dug 1.6 feet (0.5 meter) deep in soft sand or volcanic ash. The young iguanas hatch about 14 weeks later, taking almost a week to dig their way out of the nest.

Habitat and current distribution

The Galápagos land iguana is found only on the Galápagos Islands of Fernandina, Isabela, Santa Cruz, Santa Fe, Seymour, and South Plaza (the Galápagos Islands are a province of Ecuador, lying about 600 miles [965 kilometers] off the west coast of the country). Biologists (people who study living organisms) sometimes regard the population on Sante Fe Island as a second species of Galápagos land iguana (Conolophus pallidus). The Conolophus pallidus is given endangered status on the U.S. Fish and Wildlife Service's endangered species list.

Land iguanas prefer dry areas on the islands they inhabit.

History and conservation measures

Whalers and settlers began visiting the Galápagos Islands at the beginning of the nineteenth century. At that time, the Galápagos land iguana was quite abundant. When English naturalist Charles Darwin (1809-1882) visited the Galápagos island of Santiago in 1835, he found the island covered with their burrows. Today, the Santiago Island land iguanas Darwin wrote about have disappeared.

Galápagos land iguanas did not fall prey to the settlers or even native predators (snakes and hawks). Instead, they were decimated by introduced predators, such as the cats, pigs, dogs, goats, and other domestic animals the settlers brought to the islands. Over time, many of these animals escaped or were abandoned. They became wild and their populations grew on the islands. Wild pigs dug up iguana nests to feed on the eggs. Wild cats killed young iguanas, while wild dogs killed adults. Wild goats fed on the iguana's food source.

In 1959, the Ecuadoran government declared all uninhabited areas in the Galápagos a national park. This declaration meant that land iguanas and other island species could not be hunted, captured, or disturbed. In the mid-1970s, a captive-breeding program for the iguanas was established on Santa Cruz island. More than 250 Galápagos land iguanas have been raised in captivity and then returned to the wild. Programs to rid the Galápagos Islands of introduced animals are in progress.