Hop on over to the photo-sharing site Flickr and you’ll find dozens of photos and videos of people eagerly feeding grapes to hungry iguanas on the beaches of the Bahamas. It looks like great fun and the iguanas obviously go crazy for the fruit, which is usually fed to the lizards on the ends of long sticks. There’s just one problem with this activity: the food is making the iguanas sick. Health conditions arising from the grapes and other foods that iguanas do not normally eat in the wild include diarrhea, high blood sugar and cholesterol as well as lowered levels of potassium and a high level of parasitic infections. All of these problems “could have deleterious effects on long-term fitness and population stability,” 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 in Conservation Physiology.