Sunday, 10 July 2016

ARAV Members in Conservation: The Cayman Blue Iguana Recovery Program - via Herp Digest

Article Provided by ARAV”HerpBleep Newsletter 6/16
Cayman blue iguanas, Cyclura lewisi, are one of the most iconic and one of the most endangered reptiles in the world. In 2002, only 10 to 25 blue iguanas remained in the wild. Their population crashed as a result of habitat destruction, predation by domestic dogs and cats, and road mortalities. Today, thanks to the efforts of Fred Burton and the Blue Iguana Recovery Programme, there are approximately 800 to 900 wild blue iguanas.

The Blue Iguana Recovery Program started as part of the National Trust of the Cayman Islands, and now also partners with the Cayman Islands Department of Environment, Queen Elizabeth II Botanic Park, International Reptile Conservation Foundation, Durrell Wildlife Conservation Trust, and the European Commission. The captive breeding program began with 21 unrelated lizards in 1990, when the wild population was around 100. Unrelated adults are bred, eggs are incubated, and young lizards are raised in captivity for 2 to 3 years. The head-started lizards are released to the wild when they are too big for Cayman racer snakes, Cubophis caymanus (Alsophis cantherigerus caymanus), their only natural predator, to eat them. It took a while to work out successful methods to breed, incubate eggs, and raise the young, but now 50 to 80 head-started juveniles are released every year.

Fred Burton has since retired from the program and Paul Watler now serves as the National Trust Environmental Programmes Manager. Until recently, blue iguanas freely wandered the trails of the botanic park. They were used to the presence of humans and allowed close observation by tourists. Sadly, 2015 brought two challenges. First, a number of iguanas were found ill with what proved to be Helicobacter septicemia. Some died, but others were treated and recovered. Second, feral and unrestrained dogs began entering the park, attacking and killing the iguanas.

All of the blue iguanas have been rounded up and are being held at the iguana breeding facility for safe keeping until a fence around the park can be completed to keep the marauding dogs out. The captive blues still can be seen on once-a-day tours of the breeding facility. The trails are gloomily empty of all except for the invasive green iguanas, Iguana iguana, which are being culled as pests. It is unknown what if any impact the green iguanas have on the blues, other than competition for food. The greens do seem to prefer the softer landscaped plants around buildings in town to the tougher native plants in wild areas.

All of the blue iguanas are marked with a unique pattern of colored beads placed in their nuchal crests so they can be identified from a distance. Walking through the botanic park we were lucky to spot a wild-born juvenile with no beads that so far had eluded capture and marking.

While visiting Grand Cayman I was invited to participate in the release of a group of head-started blue iguanas. As part of the pre-release health assessment, I got to take blood samples form 26 juvenile blue iguanas. It was an unseasonably cool morning and the iguanas were cold and slow. We normally take blood from the ventral caudal vein in the tail, but it wasn’t flowing well with the cool temps so we switched to the jugular vein. The syringes filled quickly with minimal stress to the patients. The pre-release testing included CBC, chemistry panel, fecal parasite screen, and blood screening for Helicobacter.

A few days later we met the National Trust team in Collier’s Wilderness, the most remote part of the island, to release a group of 8 head-started blue iguanas to the wild.
We hiked off-road along an unmarked trail over the iron shore (jagged limestone) for some 45 minutes and located the preplaced iguana hides by GPS. The trail was as rough as I’ve ever seen and it tore up and ruined my athletic shoes. Biologists for the National Trust said a good pair of hiking boots only lasts a month on these trails.

The entry holes of the wooden hides had been blocked to keep other iguanas and crabs out so that each hide was ready for the new release. If the blocker had been dislodged, a scope was used to ensure the hide was empty. The iguanas were placed in the hide head first, one per hide. They typically ran to the back of the hide and stayed there. Releases take place in the late afternoon. The iguanas usually start to venture out of the hide the next day, but have a safe place to which they can retreat. They stay with the hide for days to months before establishing their own territory. Monitoring of the population shows the survival rate of new releases to be very high, approaching 100%.
Surveys of the wild population are done annually. Established adults maintain territories and force new recruits to find their own territories as they mature, thus not every iguana can be counted and statistical models are used to estimate the population. The Blue Iguana Recovery Programme is close to achieving their goal of a self-sustaining wild population of over 1,000 blue iguanas. It will take constant monitoring to keep the population viable.

See Blue Iguana Recovery Program on Facebook.
Stephen Barten, DVM
Photos by Stephen Barten, DVM and Hillary Rosenthal
***At this time ARAV would like to extend a special thanks to Steve Barten. Steve has donated his amazing photography to ARAV for several years and the beautiful images on our website, newsletter headings, and other materials are all due to his generosity. We can’t wait to see the photos from his next great herping adventure!

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