From tourists handing potato chips to squirrels to those tossing bread to ducks, so many people are obsessed with feeding wildlife. But giving food to wild animals can threaten their health and safety.
Researchers recently have found that feeding iguanas leaves the animals in a precarious health situation.
“Often, seemingly innocuous actions like feeding animals can impact their health and survival, especially if these small actions are compounded by frequency and volume of the interactions,” Chuck Knapp, vice president of conservation research at Shedd Aquarium in Chicago and an author on the study, tells Treehugger.
“The daily feeding of wildlife with unnatural food items can modify behavior, which can lead to dangerous human-animal interactions, and can also cause animals to congregate around food sources and increase aggression among individuals.”
For their study, researchers were interested in the Northern Bahamian rock iguanas on the Exuma Islands who are often fed grapes by sightseers. They were curious how this unnatural, high-sugar diet might have an impact on the reptiles’ health.
It’s been nearly two decades since Bahamian rock iguanas have been assessed by the International Union for the Conservation of Nature (IUCN). But as of 2004, the species was listed as vulnerable with population numbers decreasing.
They face threats from habitat loss, illegal hunting, and predators like dogs and pigs. They’ve also been captured for the illegal pet trade. As the area has become more popular with tourists, there’s more contact with humans and the iguanas are hemmed in with no place else to go.
The impetus for the study is to understand the effects of tourism and feeding on the iguanas in order to help with the development of a sustainable tourism plan for the country, Knapp says.
“We also hope that the research findings provide a scientific platform for other countries to consider sustainably managing the interactions of tourists and wildlife for the benefit of both wildlife and to protect the tourism industry as an important economic driver for so many,” Knapp says.
Over the past two decades, the remote Exumas have seen a noteworthy increase in the number of tourists who visit, both during day trips and on yachts that pass through the islands. Just 25 years ago, Knapp says, some of the islands had zero to 20 visitors a day. Now they receive more than 200 tourists each day.
“Our team has been studying these iguanas for up to 40 years and we noticed changes in behavior and the consistency of their feces, which believe it or not can tell a lot about the health of an animal,” Knapp says.
“We decided to study several elements of the ecology and physiology of the iguanas so that we could provide a holistic understanding of how increased tourist visits and feeding with unnatural foods were affecting these endangered animals.”
Working With Iguanas
In earlier research, scientists had already found baseline blood glucose levels were higher in iguanas that were exposed to tourists, which suggested the reptiles’ glucose metabolism might be affected when people feed them nonnatural foods. So scientists created a challenge to see how well the iguanas could metabolize glucose over time because poor diet can have a negative impact on this processing.
In a lab experiment, they chose to work with the common green iguana, which is not endangered. They supplemented their regular diet with either a high or low glucose drink. The low glucose drink mirrors what is found in grapes.
Then the team traveled to the islands and gently collected 48 rock iguanas: 24 from islands that tourists don’t visit and 24 from islands frequented by tourists. They collected small blood samples and fed each iguana a glucose drink and monitored their blood sugar responses.
The iguanas from the islands where tourists frequently fed them had the highest glucose peak, a finding the researchers said was concerning.
Initially, they found the iguanas living on visited islands had some different blood values than those on tourist-free islands, including elevated glucose concentration.
“We followed up this initial work with the glucose tolerance test and found that, after consuming sugary foods, blood glucose levels spiked higher in iguanas fed by tourists and remained elevated longer over time, relative to iguanas not visited and fed by tourists,” lead author Susannah French, professor and associate head of biology at Utah State University, tells Treehugger.
“This effect was also evident with higher spikes in the blood glucose of lab animals that were regularly fed extra glucose (mimicking the tourist feeding). From these results, it is clear that regular ingestion of nonnatural, high sugar content foods is affecting these animals’ glucose regulation. We are still working to understand the long-term health ramifications of these effects for the iguanas.”
The results were published in the Journal of Experimental Biology.
Long-Term Survival and a Management Plan
The findings are important because they highlight how potential health issues could affect the reptiles’ long-term survival.
“A typical visitor to these islands would suspect that the iguanas were doing fine. They are big, active, and plentiful on islands visited by tourists. These outward indicators are possibly masking internal health consequences that can cause a rapid decline in population health if we don’t continue to monitor the activity and investigate ways to mitigate the physiological consequences of the activity,” Knapp says.
“Equally important, we hope that these findings lead to a science-based management plan that also protects livelihoods reliant on tourism. Many tour operators showcase the incredible wildlife of the Bahamas, and our research can be applied to inform strategies that are a win-win for wildlife and tour operators.”
Researchers point out that there are serious implications to how people interact with wildlife, particularly those that are endangered.
“Bahamian iguanas are incredibly vulnerable and face many threats to their existence, such as loss of habitat, invasive species, and climate change. Many of these threats are very difficult to address, but reducing the impact of human interactions like feeding is a simple way we can help endangered species through simple behavior change,” says Falon Cartwright, director of science and policy at Bahamas National Trust, the national park management authority in the Bahamas, in an email to Treehugger.
“We hope this study will help raise awareness of the plight of Bahamian Iguanas and highlight the need for a national level sustainable wildlife interaction policy and best practices guide.”
