Grapes Sicken Iguanas in Bahamas


It’s a common sight in many places around the world, iguana species have learned to gingerly approach people for handouts. Non one’s studied this ’till now. According to Charles Knapp, director of conservation and research at Chicago’s John G. Shedd Aquarium and the lead author of a new study of the iguanas published last week inConservation Physiology iguana’s are getting really sick as a result of our best intentions. Grapes are number one on list (with other handouts) is causing diarhea and even abnormally high sugar and cholesterol levels in a species of iguana found in the Bahamas. Also, potassium levels have fallen (making the lizards more prone to disease), and levels of parasitic infections has gone up. All this has begun to impact the population of the large lizards.

Bahamian rock iguanas (Cyclura cychlura) live on the islands of Andros and Exuma and several small nearby cays in the island chain. Although not technically endangered, they are considered vulnerable to extinction, with a total wild population of fewer than 5,000 individuals. That count covers the entire species, which also includes three subspecies, two of which are endangered and one of which is critically endangered.

As Knapp and his fellow researchers wrote in the paper, the feeding of wildlife is “an increasingly popular yet under-studied tourism-related activity” that is often sanctioned and encouraged for both marine and terrestrial animals. Sometimes that is beneficial, providing the animals with access to low-stress nutrition and humans with a positive conservation experience. Other times, however, feeding wildlife can cause problems, especially if it includes items from outside of their native diets. Consequences can include nutritional imbalances, obesity or behavior changes that have harmful long-term effects.

Knapp and his team wanted to find out if the hundreds of weekly tourists visiting iguana habitats were having a positive or negative effect on the animals’ health. They traveled to the islands in 2010 and 2012 and examined iguanas that interact with tourists as well as those in more isolated locations. They found that both groups of iguanas appeared the same externally but the tourist-fed iguanas—especially the more aggressive males—showed signs of nutritional imbalance. Many had diarrhea, all of them carried parasites and their blood showed abnormal levels of calcium, glucose, potassium and uric acid. The tourist-fed males also had aberrant amounts of cholesterol, copper, magnesium and other nutrients. The paper links the high-sugar, low-potassium levels to the grapes, Ground beef and other animal proteins could be causing the high cholesterol and uric acid levels found in the iguanas. (The iguanas are normally herbivorous.)

While the well-intended tourists are doing the Bahamian rock iguanas no favors, far more detrimental is loss of habitats, and various introduced species. And unbelievably, these iguanas are still caught for food.

In a press release Knapp said that it’s unrealistic to expect tourists to stop feeding the iguanas. “Instead,” he suggested, “wildlife managers could approach manufacturers of pelleted iguana foods and request specially formulated food to mitigate the impact of unhealthy food. Tour operators could offer or sell such pellets to their clients, which would provide a more nutritionally balanced diet and reduce non-selective ingestion of sand on wet fruit.” Done right, the authors suggest, tourism could actually benefit the iguanas and give them the nutrition and safety they need in order to boost their populations.

Interestingly, grapes have been found in recent years to be toxic to dogs. Is there a change in our grapes? How much of an issue are the grapes? Is it because they are grapes, or is it just that grapes aren’t typically a part of the iguana diet?