Tourists causing spike of blood-sugar levels in Bahamian iguanas

(CN) — On the Exuma Islands, tourists happily feed grapes to the Northern Bahamian rock iguana. The reptiles' blood sugar levels are rising because of it.

A group of researchers studied the rock iguanas to see how a steady supply of grapes from eager sightseers affected the creatures' diet. Published in Journal of Experimental Biology, the study first focused on the effects of high glucose intake in the more common green iguanas. The researchers wanted to test their theory on the green iguanas before they studied the critically endangered rock iguanas.

“The Northern Bahamian rock iguana (Cyclura cychlura) is an endangered species, with small populations and restricted a range that makes it at high risk to extinction,” said Falon Cartwright, director of science and policy at the Bahamas National Trust (BNT). “It is a Bahamian endemic which means it occurs nowhere else in the world but the Bahamas. It is a species of national significance."

After 17 days of feeding the captive green iguanas either a high (5g/kg) or low (2.5g/kg) glucose drink, study author Dale Denardo of Arizona State University gave each iguana an intermediate strength glucose drink (3.75g/kg) and monitored their blood glucose.

He found that when they fed certain green iguanas the high glucose diet, the animals had the most difficulty regulating their blood sugar levels.

With that research done, it came time to study the rock iguanas.

Next came what Charles Knapp, vice president of research at Chicago’s Shedd Aquarium, called “gently capturing” them.

“Over countless years of perfecting the technique, typically what we do is work in teams and we get close enough to an animal to anticipate where it moves so we can gently put a net over it. And then we very quickly restrain it to keep it calm," Knapp said in a phone interview.

Within three minutes of capture, the researchers took a quick blood sample to establish a baseline blood sugar level with which to compare their research.

The researchers captured 48 rock iguanas, 24 from islands tourists frequent and 24 from islands too rugged for tourists to reach. Divided into two groups, the study authors fed both groups the high glucose diet to measure the creatures' responses.

Much like the green iguanas fed the high glucose diet, the rock iguanas from tourist-frequented islands — often fed with grapes or whatever scraps the tourists found on their boats — had the most difficulty regulating their blood sugar levels.

Susannah French, professor of biology and associate department head in the biology department at Utah State University, said a human with these results could be seen as diabetic. But she said it's too early to understand the full effect on rock iguanas, especially considering they live at least 40 years.

“Some of these more subtle effects are hard [to fully understand]. The idea of adding physiology to try to understand the health impacts will hopefully give us a quicker look of the bigger picture of what’s happening in these populations," she said.

Cartwright said the results should serve as a cautionary tale regarding tourism and wildlife.

“There are serious implications to how people interact with wildlife, especially endangered species,” he said, adding he hopes the study “will highlight the need for a national level sustainable wildlife interaction policy and best practices guide.”

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