Tourists: Stop feeding junk food to iguanas

On islands in the Bahamas, tourists routinely feed iguanas grapes, cereal, ground beef, and even potato chips. This unnatural diet could be affecting the health of these endangered reptiles, researchers warn in Conservation Physiology. Iguanas on heavily-visited islands tend to have higher levels of blood sugar, parasite infection, and diarrhea.

Feeding wildlife isn’t always a bad thing. If done properly, it can improve a species’ nutrition and survival, as well as encourage people to view conservation positively. But potential problems abound: Unnatural foods can lead to nutritional or metabolic problems, and animals may begin to congregate near the food source, increasing territorial fights and the spread of disease.

One frequently-fed species is the Northern Bahamian rock iguana, which lives on eight small islands, called cays, in the Bahamas. Back in the 1980s, only a couple dozen people visited the cays per day. Now that number has jumped to 150, and tour companies often include iguana feeding as one of the perks.

During trips in 2010 and 2012, the study authors caught iguanas on some islands popular with tourists and islands that were usually left alone. They measured the animals’ body condition, took blood samples, and examined stools.

The iguanas on the two types of islands had similar body condition and stress levels, the team found. But iguanas on the visited islands were much more likely to be infected with parasites such as hookworms and pinworms, and their fecal samples were more liquid. They had higher levels of glucose and uric acid in their blood and lower levels of potassium; males also had higher levels of cholesterol, triglycerides, and some minerals.

The high sugar levels and diarrhea might be the result of eating too many grapes, the authors speculate. Meat and starchy foods could have contributed to the cholesterol and triglyceride increase, and sand coated on the grapes could have changed the animals’ mineral levels.

But iguana feeding doesn’t need to be banned outright, the researchers say. Instead, tourists could feed specially-formulated pellets to iguanas that provide the correct blend of nutrients. Roberta Kwok | 6 December 2013

Source: Knapp, C.R. et al. 2013. Physiological effects of tourism and associated food provisioning in an endangered iguana. Conservation Physiology doi: 10.1093/conphys/cot032.

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