Archives of The Cold Blooded News

The Newsletter of the Colorado Herpetological Society

Volume 31, Number 8;   August, 2004

West Indian Rock Iguanas

by Richard A. Searcy

Unlike their green cousins, Cyclura iguanas are terrestrial animals. Generally they inhabit hot, dry areas where they spend most of their time on the ground. Cycluras can climb, however, and juveniles probably climb more than adults. to escape predation. I have personally witnessed an adult Ricord's iguana climb into a one meter tall mesquite bush to reach small berries near the top.

Cycluras tend to be more robust than Iguana iguana, and generally have a shorter, heavier tail. Their larger size, as well as a much different habitat than the rain forest canopy that green iguanas typically occupy, leads to most Cyclura iguanas digging dens for shelter and nesting. These dens can be from two to several dozen feet long with multiple branches and chambers.

Rock iguanas are generally herbivorous as adults. They will consume the leaves, fruits and flowers of various plants found in their habitat. Juveniles will eagerly eat invertebrates, and depending on the availability of food, adults will also eat invertebrates and even scavenge carrion. A park ranger on Isla Cabritos in the Dominican Republic related a story in which a large adult Rhinoceros iguana (Cyclura cornuta cornuta) stole and consumed pork that the ranger had placed on a low hanging branch to dry.

Cycluras typically breed during the spring rainy season and begin nesting during the following dry season. Nests, like dens, can be of varying length and complexity. Hatchlings begin emerging from the nests in the fall which usually coincides with a second rainy season.

As I stated earlier, Cyclura iguanas range from vulnerable to critically endangered. In the past, iguanas were a food source for native islanders. This probably placed pressure on populations that were never extremely high to begin with. European colonization of the islands had a more profound effect on iguana populations. Degradation of habitat continues to threaten the future of these animals. Perhaps the most devastating effect on the iguanas came from the introduction of domesticated animals. Cattle, horses, burros, cats, dogs, mongoose and rats all have a negative effect on iguana populations either through predation or competition for habitat and food.

The Grand Cayman Blue Iguana (Cyclura nubila lewisi) is presently believed to be the most critically endangered species with possibly fewer than 20 wild specimens remaining. This strikingly blue iguana once ranged throughout the Cayman Islands. Jamaican iguanas (Cyclura collei) were thought to be extinct until recently when a breeding population was discovered in the remote region of the Hellshire Hills. Ricord's iguanas (Cyclura ricordi), which share habitat with the larger Rhinoceros iguanas on the island of Hispaniola, are still plentiful in remote regions, but they are declining in numbers. Similar stories abound for the other species of Cyclura iguanas as well.

The good news is that there are many conservation efforts ongoing for these spectacular lizards. The Indianapolis Zoo has been involved with Cyclura conservation for many years. The zoo has been very successful in breeding several species and is currently working with Grand Cayman Blue iguanas and Jamaican iguanas. Research is also being conducted with Ricord's and Rhinoceros iguanas. Many other institutions, including San Diego Zoo and Fort Worth Zoo, are also involved with the conservation of iguanas. If you are interested in learning more about the natural history and conservation of West Indian Rock Iguanas, here are a few web sites that have a lot of great information:

• http://www.cyclura.com
• http://www.blueiguana.ky/
• http:/www.iucn-isg.org/
• http://www.scz.org/_private/iguana/meet.html