Heat-sensing cameras used to search for iguanas

After successful trial, camera drones could aid cull

Researchers are aiming to use high-tech, heat-seeking camera drones – similar to those used by police and the military – to seek out green iguanas on the Sister Islands.

The Department of Environment experimented with the technology when a team of visiting scientists came to Grand Cayman last year. Thermal imaging cameras have been used for some time to spot birds and mammals, but it was not known if the technology could work on cold-blooded reptiles.

The DoE’s terrestrial resources unit teamed up with researchers from the University of Harrisburg, Pennsylvania, to put the technology to the test in a trial deployment at the Botanic Park in December.

The thermal imaging camera detects an iguana in a tree in the Queen Elizabeth II Botanic Park during a test run in December.

Fred Burton, head of the unit, said the trial had proved successful, enabling researchers to locate green iguanas in the foliage, using a drone and thermal imaging camera. He believes this could be useful in searching for the invasive lizards on the Sister Islands, where they are currently beginning to get a foothold. Eradicating the nascent population before it becomes established could prevent Cayman Brac and Little Cayman from experiencing similar issues to Grand Cayman where the exponential growth of the green iguana population has caused a host of environmental problems, resulting in a multi-million dollar culling program.

Mr. Burton said searching for the fledgling green iguana population on the Brac was currently like looking for a “needle in a haystack.”

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He said using drones carrying thermal imaging cameras in combination with high-resolution video cameras would allow researchers to precisely locate iguanas and determine the species. They could then direct cullers to the location.

He believes the technology could also become useful on Grand Cayman as the islandwide cull begins to take its toll.

“If we are really successful over time and we get the numbers down even further and we need to find them in more remote locations, like the Central Mangrove Wetlands, this could be very useful,” he added.

Thermal cameras, which allow biologists to “see” animals previously hidden to the naked eye, have become a common tool for surveying various species.

Scientists Albert Sarvis and Christine Proctor from Harrisburg, and Bernardo Mesa from Elizabethtown College, who pioneered the use of the technology to spot snakes in a study in the U.S., were involved in the test deployment at Grand Cayman’s Queen Elizabeth II Botanic Park in December.

Writing in the DoE’s in-house journal Flicker, Ms. Proctor said high-tech camera drones were becoming more affordable, making them an option for researchers.

“Although this heat-sensing technology is easily used with endothermic (‘warm-blooded’) species, we believed that it could also help find ectothermic (‘cold-blooded’) species, potentially revolutionizing the way we search for reptiles,” she wrote.

An initial test, at sunrise, proved unsuccessful, because the iguanas were the same temperature as the foliage. As the sun rose, the iguanas began to stand out on the thermal images.

“As it turns out, the iguanas warm up faster than the vegetation and maintain a slightly higher temperature throughout the day. We had confirmation that thermal cameras could indeed be used to spot a reptile,” Ms. Proctor wrote.

After the success of the trial, Mr. Burton says the DoE is contemplating purchasing drone and camera equipment to aid its iguana surveys and to assist with culling on the Sister Islands.

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