Cyclura - Diet and Longevity

Diet and Longevity

All rock iguanas are herbivorous, consuming leaves, flowers, berries, and fruits from different plant species. A study in 2000 by Allison Alberts of the San Diego Zoo revealed that seeds passing through the digestive tracts of rock iguanas germinate more rapidly than those that do not. These seeds in the fruits consumed by cycluras have an adaptive advantage by sprouting before the end of very short rainy seasons. The iguanas are an important means of distributing these seeds to new areas (particularly if females migrate to nesting sites) and, as the largest native herbivores of many island ecosystems, they are essential for maintaining the balance between climate and vegetation. Their diet is very rarely supplemented with insect larvae, crabs, slugs, dead birds, and fungi; individual animals do appear to be opportunistic carnivores.

Like other herbivorous lizards, the rock iguanas are presented with a special problem for osmoregulation: plant matter contains more potassium and has less nutritional content per gram than meat so more must be eaten to meet the lizard's metabolic needs. Unlike mammals, reptile kidneys cannot concentrate urine to save on water intake. Instead reptiles excrete toxic nitrogenous wastes as solid uric acid through their cloaca. In the case of the rock iguana which consumes large amounts of vegetation, these excess salt ions are excreted through their salt gland in the same manner as birds.

The record for the longest lived captive-born rock iguana is held by a Lesser Caymans iguana, which lived for 33 years in captivity.

A Blue iguana captured on Grand Cayman in 1950 by naturalist Ira Thompson was imported to the United States in 1985 by Ramon Noegel and sold to reptile importer and breeder, Tom Crutchfield. Crutchfield loaned Godzilla to the Gladys Porter Zoo in Brownsville, Texas in 1997. The lizard was named Godzilla by the zoo staff and was kept until his death in 2004. Thompson estimated the iguana to be 15 years of age at the time of its capture. This lizard may have been the word's longest-living recorded lizard at 69 years of age, having spent 54 years in captivity.