Dozens of speedboats dock every day on the white sand beaches of the islets of the Exuma archipelago, attracting the mainly herbivorous Cyclura cychlura iguanas that can measure almost 50 centimeters.

Reptiles classified, according to the subspecies, from "vulnerable to "in danger of extinction".

The big lizards then come running for one of the attractions of these "eco-tourist" outings, hand-feeding with skewers of grapes.

A team of American researchers had the idea of ​​studying the effect of this food, which is as repeated as it is unnatural, on the metabolism of animals.

For this, they compared the glucose level in the blood of iguanas, comparing it to that of animals of the same species, but living in nearby islets whose topography prevents the arrival of tourists.

Final result of their work on four populations of iguanas (two fed on grapes, two on natural food), published in the Journal of Experimental Biology.

There are "significant effects" on iguanas fed by tourists, which have much higher blood glucose levels.

To ensure that it is indeed the grape feeding that causes this hyperglycemia, they reproduced the experiment in the laboratory, on common green iguanas, a non-protected species.

With identical results.

The researchers admit to themselves that they do not know if this change in metabolism is in itself bad for the health of the lizards.

But "we could call it diabetes if it was humans or mice," Susannah French, lead author of the study, told AFP.

And the researchers are already noting physiological effects, for example on excrement, "in the shape of a Cuban cigar" when the iguanas have their natural diet of plants, but much more liquid with the addition of fruit.

A previous study had already shown that the iguanas living on the beaches where they are fed are larger, heavier and grow faster than their congeners not exposed to tourists.

The researchers, who insist their study is not a condemnation of tourism, want to work with tour operators to "find a more sustainable plan," said another study author, Charles Knapp.

Among the tracks, regulate the number of visitors or "the use of another type of food".

© 2022 AFP