About Author: Tandora Grant

Posts by Tandora Grant


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.


Jamaican Iguanas Return Home

Jamaican iguana

I have just returned from a great trip to Kingston, Jamaica, to assist in the annual release of Jamaican iguanas. Every year I look forward to this trip; it’s a chance to move my computer “outside,” get my arms scratched by iguanas, and work with a fantastic group of collaborators who are my friends, too. The first few days was spent at the Hope Zoo, where we evaluated the health and growth of all the captive iguanas (202!). Staff members from the Fort Worth Zoo in Texas, the Audubon Zoo in Louisiana, and the Hope Zoo were among the cheerful hands that made this work efficient and lighthearted.

The Jamaican iguana was believed to be extinct since the 1940s, but its existence was confirmed in 1990 when a pig hunter’s dog found an adult iguana. Researchers immediately jumped to attention and discovered that a very small population of iguanas remained in a remote 3.86 square miles (10 square kilometers) of limestone karst, a dry tropical forest in the Hellshire Hills of southern Jamaica.

The greatest threat to the iguana population is from nonnative predators, including Indian mongoose and feral cats, dogs, and pigs. Mongoose are very common throughout Jamaica and are capable of killing iguanas under one kilogram. Another significant threat is illegal tree cutting for use in charcoal production, an activity that has badly degraded approximately one-third of Hellshire’s forest.

The Jamaican Iguana Recovery Group is an organization of Jamaican and international scientists, zoo professionals, and policy makers dedicated to the recovery of the iguana and biodiversity conservation in its Hellshire Hills home. The San Diego Zoo Institute for Conservation Research™ has been a collaborator in this recovery effort since 1993. A central focus of the recovery program involves raising baby iguanas in captivity at the Hope Zoo until they grow large enough to be safe from most predators. We call this strategy a “headstart for survival.” Hellshire Hills is nearly ideal habitat for iguanas, but it has very few open sunny soil patches suitable for nesting. Because of this, most wild females use one of three nesting areas. Hatchlings are collected from these sites at emergence, tagged, and brought to the Hope Zoo. After a few years of growth, the iguanas are returned to their home and released…hopefully to make more babies!

After several super-long days at the Hope Zoo, we calculated that 17 iguanas were ready for release, and we got ready for travel out to the Hellshire Hills. What used to be an all-day excursion, including a four-hour forest hike, the trek to the release site is now much easier with access by boat and only a one-plus hour hike. The core iguana habitat is encircled by a series of traps that keep the iguanas safe from mongoose. As long as the small iguanas stay within this core zone, their chance of survival is good. A team from the University of West Indies in Kingston heads the field research component of this project and monitors the wild iguanas, assesses biodiversity of all herpetofauna, and keeps the mongoose traps operating.

After one last looking over, we all took turns letting the iguanas out of their “repurposed” pillow cases. Most zoo professionals only see these fabulous large lizards in managed care, so to be able to return one to the wild is very rewarding! We released them at the core soil nesting sites so that they will remember where to find them again. With calls of “good luck, make lots of babies,” we headed happily down the hill back to our beach camp.

Since 1996, we have now repatriated 155 iguanas back to their Hellshire home. Though the program has a long road ahead before recovery is assured, field research has documented several milestones including: a greater than three-fold increase in the number of nesting females, successful reproduction among repatriated releases, and long-term survival of hatchlings (and other herpetofauna) within the core mongoose trapping area. Few people can say they have helped bring a species back from the edge of extinction, and I am very proud to be a member of this awesome team. Really, how cool is that?

Tandora Grant is a research coordinator for the San Diego Zoo Institute for Conservation Research.