It should come as no surprise that the population of the invasive Green Iguana has reached epic proportions over the past decade. The Central American reptile, which at one time was listed as a protected species until amendments were made to the Animals Law in 2010, have become an increasingly common sight in the Cayman Islands.
Sightings of Green Iguanas first emerged in Grand Cayman as early as 2002. Ten years later by the 2012, the reptile had expanded its territorial reach and made the crossing to the Sister Islands and soon thereafter they were deemed to have “invaded” the Cayman Islands in a similar manner as has the notorious Lion Fish.
Since 2014 the Department of Environment (DoE) has been conducting population estimates on Grand Cayman, with a total estimated population of 200,000 identified in August 2014, increasing to 300,000 in August 2015, doubling every 1.5 years according to the DoE studies. If these trends continue, Frederic Burton of the Blue Iguana Recovery Programme said last week that “we might expect the population number to increase to around 500,000 by August 2016”.
In what started as being no more than a nuisance to local gardeners, the explosion of the Central American reptiles are now said to be posing a real threat to the islands’ natural resources and potentially leading to the extinction for some indigenous Flora and Fauna species, including the Red Birch Tree and the already endangered Blue Iguanas.
Speaking to The Cayman Reporter, Frederic Burton said, “As the Green Iguana population grows, the impact on the environment is expected to grow with it. They are capable of living at very high population densities, which quickly leads to depletion of their preferred food sources.”
The herbivores, who have no natural predators in Cayman, are said to have the capacity because of their growing numbers to potentially exhaust the endangered Blue Iguana’s food supply, leading to further reduced numbers of the Blues, which are found only in the Cayman Islands.
Mr Burton also agreed with sentiments that were first shared in the public domain in early 2014 by the National Trust, which stated the immediate concern was the impact on local vegetation.
In 2014 Paul Watler of the National Trust said that “Our ecosystem is not adapted to having a huge reptile population that’s constantly foraging on our vegetation.” Speaking to The Cayman Reporter Mr Burton acknowledged the further threat of extinction of the local Red Birch Tree, as well as a depletion in food sources for a number native woodland birds, as a result of the population explosion of the Green Iguana.
Mr Burton said, “In recent years the iguanas have turned to Red Birch trees, and are eating all the flower shoots as soon as they appear. They are also eating the new leaves as they emerge at the end of the dry season. Without flowers, the Birch trees cannot fruit. This deprives a whole range of native forest and woodland birds from one of their staple food sources. Meanwhile the Birch trees are gradually weakened because they are unable to mature enough leaves to sustain themselves”
In an attempt to deal with the growing threat of the Green Iguana, the DoE announced last week its plans to commence the second of two trials, which are designed to assess different options to tackle the exponentially increasing population of invasive Green Iguanas in Cayman.
The first trial has just been completed, according to a press conference held by the DoE on Friday 17 June which involved three contracts with experienced Green Iguana hunters, each in a defined area. Using licensed air rifles and small teams, over two weeks, each these contractors were challenged to reduce the Green Iguana population density in their designated area, by at least 90 per cent. DoE staff conducted intensive survey work before and after this trail, to accurately measure the impact of the culling.
The second trial began on the week of 20-26 June. This will test the logistics and effectiveness of involving larger numbers of people in culling over larger areas of the landscape. Eighteen cullers have formally been registered, drawn from a group who attended a public meeting on the future of green iguana control in 2015.
Each registered culler is free to involve as many additional people they wish, under their primary registration. Registered cullers will receive $5 per green iguana delivered to the DoE under their registration ID, during the cull week. This effort will concentrate mainly on western Grand Cayman, where the green iguana population density is the most extreme, though some cullers will operate in other areas, the DoE said.
Cullers are required to be reasonably humane in their methods, and may be using a variety of techniques ranging from air rifles and nooses to hand capture. Cullers are advised however that they do not have any additional rights of access on to private property, and so, with the assistance of the DoE will be requesting permission from owners to cull in many locations.
The community is asked to cooperate to the extent possible, bearing in mind the green iguanas have become a major public nuisance and a potentially devastating environmental threat.
While these culls are expected to bring temporary reductions of green iguana numbers in some areas, they will not be sufficient to prevent continued population expansion overall. Both the DoE and the National Conservation Council hope that the information and experience gained from these trials will help to design an effective plan to tackle the Green Iguana problem at the necessary scale, and to estimate what the implementation of such a plan may actually cost.
In addition to the growing numbers of Green Iguana’s, Mr Burton also indicated that a possible “new strain” of iguana’s are emerging.
“We know that our green iguana population is derived from multiple sources, and it is quite likely that we may have a mix of strains from both Honduras and South America. Geneticists are beginning to think there are three or more different species of Green Iguanas, and if they are right, what we have here may be a hybrid strain,” Mr Burton said.
However, he added, “We will know for sure when genetic samples being sent from here are analyzed.”