Saving the Brac rock iguana

The first Cayman Brac rock iguana population study has presented alarming results – only 97 Brac rock iguanas have been found.  

Since the count started in January 2012, at least six of the 55 known, breeding adults have been killed.  

A subspecies of the Cuban rock iguana, the Brac rock iguana (Cyclura nubile caymanensis) had been reclassified from endangered to critically endangered by the IUCN (International Union for Conservation of Nature) Red List even before the study commenced.  

Initiated in 2011 by a group of concerned stakeholders and spearheaded by the Department of Environment and the National Trust for the Cayman Islands, the ongoing census continues to evolve to spur reproduction and prevent early death of these vulnerable creatures for the rejuvenation of the rapidly declining population. 

Overseeing the population study in the Brac is Bonnie Scott Edwards, Cayman’s 2012 Conservationist of the Year. Self-described as “an English teacher,” Ms Edwards first learned how to handle iguanas while working in the Bahamas in 2005 with Dr. Charles Knapp of the Shedd Aquarium in Chicago. Edwards further developed her skills in 2008 while studying Indonesia’s Komodo dragons. 

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To launch the count, Ms Edwards created a telephone hotline for people to report iguana sightings. She and her husband, Gene, also placed posters around the island and passed out business cards to people who typically work outside, encouraging them to report sightings. Several iguanas that were eventually trapped and pit tagged had been observed for many years by Brac families.  

With a significant donation of traps from the Department of Environment, Ms Edwards and other researchers, some also trained by Dr. Knapp, as well as a team of local volunteers trapped and pit tagged 97 iguanas, their length, weight and gender recorded.  

Pit tagging includes the injection of an electronic tag just under the surface of an iguana’s skin. All relevant data about the iguana are entered into a database. When the animal is recaptured it can be identified by the pit tag; growth, migratory patterns and other variables can be compared with previous recordings.  

Coloured beads of various patterns were also attached to the iguanas’ crests for future identification from a distance. All iguanas were releasing into the wild.  

The initial phase of the study has included not only a population count but also identification of nesting sites. Preferring sandy areas along the coast, adult females lay from one to 25 eggs in a single clutch, usually once per year coinciding with the rainy season.  

A single nesting season lasts about six weeks. The “Honeymoon Cottage” area at the South Side is one of the largest nesting sites in the Brac. Other nesting areas include West End Community Park and along Bluff West Road.  

The Cayman Islands Government’s Nature Tour Guide and volunteer with the iguana study, Keino Daley explains that on Bluff West Road iguanas actually approached volunteers, indicating that people had been feeding them. In other parts of the island, iguanas were less friendly, forcing volunteers to roll down their shirt sleeves and trudge through the bush, looking for tail drags, droppings and claw marks. One volunteer crawled under a house to retrieve an iguana. 

“I was surprised that iguanas love manchineel fruits,” Mr. Daley explains. “In one area, we really had to be careful because there were several iguanas sighted near a lot of manchineel trees.”  

The manchineel tree produces a milky, white sap so toxic that, historically, Carib Indians used it to poison their spears, and the tree’s fruit is one of the most poisonous in the world to humans. As a nature guide, Mr. Daley states that he does not take tourists to known nesting areas to protect the iguanas.  

Two looming threats to the iguana population are feral cats that eat hatchlings and unrestrained dogs that kill adults. Failure to adequately control either has resulted in significant iguana population loss. While the Humane Society assists with spaying and neutering of stray cats, all signs indicate that the feral cat population thrives.  

Ms Edwards commends the Humane Society for trying to control the stray cat population but suggests that culling stray cats offers a faster means of protecting iguana hatchling populations. Mr. Daley noted that some iguanas had to be relocated because they were threatened by stray cats and dogs in their immediate surroundings. 

Other threats to the iguana population are careless motorists. As mentioned, six mature iguanas have been killed on the roadways since the count commenced. Whenever an iguana is found dead on the road, news spreads rapidly by word of mouth and social media. For a family that has watched an iguana for years, the killing of that iguana is similar to losing a beloved family pet.  

Ms Edwards also discourages tourists and other admirers from feeding these animals. She suggests that iguanas crawl to the roadway not only to bask but to gather food that humans have left for them, eventually associating traffic with food. Most of the road-kills have occurred at South Side Road.  

In response to these deaths, Ms Edwards surveyed the public asking what can be done to halt the killings of mature iguanas. The Department of Environment has approached the National Roads Authority with the results of the survey to seek assistance with road signs and other traffic calming measures.  

Ironically, the climbing, non-endemic Central American green iguana thrives in Grand Cayman whereas the endemic Brac rock iguana struggles to survive as a subspecies. Because it cannot climb, the Brac iguana has a less varied diet of leaves and fruits found on the ground, and the animal is much less capable than the climbing, green iguana of evading predators. 

To further the study, in June 2013, volunteers will take blood samples for a DNA analysis of the Brac and Little Cayman rock iguanas to see how closely they are related. Although the National Trust website points out that it is now illegal to move any iguanas from any of the three Cayman Islands except for authorised conservation purposes, iguanas from the Sister Islands have been co-mingled over the years. Eventually, radio transmitters will be placed on selected Brac iguanas to track their migratory patterns.  

Human development is also of concern. Although Cayman Brac is sparsely populated, pockets of development are believed to have forced the iguana population to shift in some areas. The National Trust endeavours to purchase land for conservation areas, and developers are encouraged to be mindful of the habitat of these critically endangered animals. 

The critically endangered Brac rock iguana population is a unique feature of the island that must be protected and allowed to repopulate before it becomes extinct. 

Since the count started in January 2012, at least six of the 55 known, breeding adults have been killed.  


Volunteers mark a captured rock iguana during the count that began in January 2012 in Cayman Brac. – Photo: File
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