Iguana Specialist Group


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.


Lizards of Guatemala

A large male Guatemalan beaded lizard relaxes in one of the outdoor breeding pens.

I was recently in Guatemala for the 15th annual meeting of the International Union for the Conservation of Nature (IUCN) Iguana Specialist Group (ISG). Thank goodness for acronyms! As the name implies, the group is focused on the conservation and preservation of iguanas. These large, herbivorous lizards are found throughout much of the New World’s tropics and subtropics. Many iguana species are threatened with extinction due to hunting (apparently they taste like chicken), habitat loss associated with agriculture and development, introduced predators, road kills, and other human-associated threats.

Part of the meeting included a workshop focused on local iguana species, one of which occurs in Guatemala’s Montagua Valley. After the meeting and workshop, the group took a field trip to this valley to see these iguanas and to visit the conservation-breeding program for one of Guatemala’s other rare and endemic species, the Guatemalan beaded lizard, a close relative of the Gila monster found in the deserts of the American Southwest.

Thanks to the efforts of local conservationists, the future for both the iguanas and beaded lizards of the Montagua Valley is looking brighter.

Glenn Gerber is head of the San Diego Zoo’s Caribbean Regional Program. Read his previous post, Iguanas: Why Move?