Contract hunters would need to cull nearly 200,000 green iguanas per year at an estimated cost of more than $1 million to make an impact on the exponentially increasing population of the invasive species.
A Department of Environment report on two test culls held earlier this year indicates that a sustained culling project would likely generate around 200 tons of iguana carcasses annually – equivalent in weight to about 80 adult elephants.
Fred Burton, who led the pilot project, said the test culls proved effective but chaotic. Overall he said the results of the pilot were “discouraging” and the scale and cost of the task was greater than originally hoped.
He highlighted a series of potential problems that the country faces in scaling up eradication efforts to the necessary level, including disposal of the carcasses.
“The scale of the green iguana control challenge exceeds DoE’s current capacity, and requires government to consider options to resource this major undertaking,” Mr. Burton wrote in his report.
“DoE estimates a cull of 177,500 adult and sub-adult iguanas per year will be necessary to initiate a decline in the green iguana population if we begin the operational cull in 2017. This implies an operation almost 10 times larger than the recent experimental culls.”
The report cites earlier surveys that indicate the green iguana population is doubling every 1.5 years “threatening a catastrophic impact on the natural environment and socially unacceptable problems for agriculture, infrastructure and residential areas.”
Against this backdrop, the Department of Environment organized two test culls in June this year. The first involved three teams of skilled hunters working to eradicate iguanas in three specific areas with high iguana population densities.
The second involved teams of licensed “bounty hunters” who were paid $5 a head for their catch. A total of nearly 19,000 iguanas were culled in the two week-long experiments.
The DoE assessed the two approaches as equally effective, though Mr. Burton’s report highlights practical and logistical concerns with using community bounty hunters over contracted cullers.
He said the demands on the Department of Environment staff, including processing, counting and administering payments, were unsustainable over the course of a longer term operation.
“Other issues with management of humane treatment of iguanas, difficulties in paying government funds to unregistered members of the public, handling of old, decomposing carcasses etc., all combine to make this a severely problematic option,” he said of the bounty-hunting approach.
Contracting trained cullers to target specific areas is viewed as a more viable option.
The pilot for this approach involved three teams of experienced shooters targeting heavily populated iguana territories at the Shores subdivision, the SafeHaven golf course, and the Britannia golf course. The mangrove habitat around the Shores development hampered eradication efforts, but cullers were able to reduce iguana populations by 90 percent on the two golf courses.
“However, as soon as the cull ended, green iguanas very rapidly re-invaded from adjacent land,” the report notes. Despite the culling of thousands of iguanas in these areas, it says the population at the target sites had rebounded to 80 percent of its original level within two weeks.
The report suggests such sites could effectively function as bait for large numbers of iguanas in a system of “honeypot hunting” with contract cullers hired to repeatedly target the same spots.
“The observed pattern of rapid immigration to recently culled sites such as golf courses (which support high densities of green iguanas), suggests that sustained culling in such areas could progressively draw in and kill iguanas from surrounding lands. A network of appropriately spaced honeypot areas could effectively clear iguanas from a much larger area.”
Another potential method suggested in the report is a progressive area-by-area cull from one end of the island to the other, with the work subcontracted to private companies.
Disposal of the vast amount of carcasses remains a hurdle, with the incinerator at the landfill site unable to cope with the demand.
“In the first year of a sufficiently resourced cull, a biomass of the order of 200 tons of iguana carcasses per year will be generated and will have to be disposed of,” the report states.
“During the June 2016 experiments it already became clear that incinerator capacity at the George Town landfill would be nowhere near sufficient to handle this kind of mass, in event it is brought back into service.
“While it is possible that some fraction of the cull may be taken for human consumption, we must expect that the vast majority will have to be received by and disposed of at the landfill facility. Arrangements may need to be developed with the Department of Environmental Health.”
The report includes an account of every dollar spent on the pilot project from expenses for gloves, boots and clipboards to checks paid to individual bounty hunters. The total, which does not include the additional expense of diverting Department of Environment workers to the culls, was $109,044.30.
Compass reporter Charles Duncan contributed to this story.