blue iguana


The Winding Road of Red-listing Reptiles

A young adult male headstarted Jamaican iguana is tagged for short-term tracking after release in the Hellshire Hills.

One of the iguanas I have worked closely with is found only on Grand Cayman in the Caribbean. When I first started collaborating with the Blue Iguana Recovery Program in 1998, the species’ numbers had declined to less than 25 in the wild, and they were classified as critically endangered. But what is the difference between “endangered” and “critically endangered” or “vulnerable”? We’ve all heard the terms, but what do they mean exactly?

The world’s definitive standard on these terms comes from the International Union for Conservation of Nature (IUCN), the largest global environmental organization and professional conservation network. The IUCN developed the Red List of Threatened Species, which is the most comprehensive database of the conservation status of plant and animal species worldwide. This database documents a species’ biology, research, threats, human use, and conservation needs and actions, all of which are evaluated against a defined set of criteria to determine risk of extinction. Government agencies, educators, conservation-based nongovernmental organizations, scientists, and others use the IUCN Red List to obtain information on the status of biodiversity, species, and ecosystems. This information is often used to enhance research, create national and international laws, and draw attention to global conservation needs and set priorities.

Tandora stands at the visitor educational sign in front of the headstart facility at the Hope Zoo in Kingston, Jamaica, where iguanas are raised until they are big enough to defend themselves against predators after release. Photo credit: Jaclyn Woods.

Scientific experts for each species provide data and analysis to the Red List database. When complete, the accounts are reviewed by two evaluators to ensure they conform to consistency standards. As program officer for the IUCN Iguana Specialist Group, I have been working with our members to bring existing assessments up to date and generate new entries for species that have not yet been evaluated. Progress on this huge task has been great: we have completed 19 assessments so far and have 40 more to do.

The process begins by gathering all known data on each iguana species; for example, how many eggs they lay and how often, the number of years it takes to reach sexual maturity, and how long they live. This information can help determine the number of years between generations and predict rates of growth or decline in the future. We also characterize the habitat and calculate land-usage patterns by the iguanas where they live. All known threats are classified and scored by severity, scope, and timing, and whether they are subject to human trade or use. Lastly, we outline what conservation and research actions are currently in place for the iguanas and where there are deficiencies that need to be addressed.

We double-check the sex of a Jamaican iguana right before release to the Hellshire Hills. Also in this photo is Byron Wilson, University of West Indies, who is head of the field component for the recovery project. Photo credit: Jaclyn Woods

Once all the data has been discussed, we turn to the IUCN’s defined set of criteria for determining the level of extinction risk, if any. Species can be endangered for different reasons. If they only occur in a very small area, a single catastrophic event can wipe them out. Or, they might still be found in several locations but are all experiencing a new and dramatic threat. Even a widespread species that appears numerous might be declining at a low level where the number of deaths is greater than the number of births.

We developed a Species Recovery Plan to outline necessary action steps, including improving care and reproduction at the small breeding facility, protecting habitat, educating the public about controlling pet dogs, and stressing the value of the iguana to the health of the forest and ecosystem. To date, we have released over 750 iguanas to three protected reserves. Because their numbers are now increasing, I am happy to report we have just published a new Red List assessment that down-lists this iguana to Endangered status! This significant milestone is certainly a morale booster for all the folks who work tirelessly to save iguanas. We can make a difference!

You can read more about my work with the Grand Cayman Blue Iguana in the November calendar issue of ZOONOOZ, San Diego Zoo Global’s member magazine, or by visiting the Blue Iguana Recovery Program website.

Read a story about Maria, a wild Grand Cayman Iguana…

Tandora Grant is a senior research coordinator for the San Diego Zoo Institute for Conservation Research. Read her previous post, Jamaican Iguanas Return Home.


A Significant Blue Birth

The San Diego Zoo’s Applied Animal Ecology Division is pleased to announce the hatching of a critically endangered Grand Cayman blue iguana Cyclura lewisi. This little female iguana hatched out of her egg on September 13, 2008, after an incubation of 92 days at 86.5 degrees Fahrenheit (30.3 degrees Celsius). She weighed only 1.58 ounces (45 grams) at hatching—a tiny little girl compared to males of her species that can grow to over 18 pounds (8 kilograms) as adults! Although our little girl is gray in color now, as most hatchlings are, adults of the species can become a beautiful powder blue color.

This iguana was a very lucky animal. About three-quarters of the way through incubation, her egg formed a small crack and started to leak fluid. This is a rare occurrence and can be caused by too much humidity, a thin shell, or many other factors. I patched the shell with plastic wrap and tissue glue and crossed my fingers. A few weeks later, I got the word that the iguana had hatched, and I ran over to the incubator room to see her. She looked good, although she had a distended belly, which usually means she hatched a bit too early and wasn’t able to absorb all of her yolk. I took her to the vets at the Harter Veterinary Medical Center, and due to the distended belly and a slight injury to the eye that probably happened during hatching, we decided she would stay with the vets. Internal yolk can usually absorb on its own as long as the animal is kept quiet and warm, but sometimes it can become infected and can even be lethal. After a week of excellent veterinary TLC, the little iguana absorbed her yolk, and her eye was healed up. She is currently waiting to be housed in the new iguana building that is near completion in an off-display area of the Wild Animal Park (stay tuned for that blog!).

Grand Cayman iguanas are considered to be the most endangered lizard in the world. Loss of habitat, introduced predators, feral animals that compete for resources, and cars all contribute to the iguana’s decline. At one point, there were as few as 20 animals left on Grand Cayman, but thanks to captive breeding, headstart and release protocols, and a new reserve system on the island, Grand Cayman iguanas are slowly starting to repopulate the wild.

Jeff Lemm is a research coordinator for the San Diego Zoo. Read Jeff’s previous blog, Frog Blog—What’s Hoppenin’?