Study shows how human food affects rare rock iguanas
By Summit Voice
FRISCO — There are plenty of good reasons to follow the old adage about not feeding wild animals, and a recent study of endangered Bahamian rock iguanas provides even more proof.
According to the findings, tourist-fed iguanas are suffering physiological problems as a result of eating human food. In the study, led by Charles Knapp of the John G. Shedd Aquarium in Chicago, the scientists compared blood and faecal samples from iguanas that were fed by tourists to samples from iguanas that did not have any interactions with humans.
The body condition of the two groups of iguanas was similar, but indicators for dietary indicators showed the effects of feeding by humans. Both male and female iguanas from the islands frequently visited by tourists showed notably different levels of glucose, potassium, and uric acid, as well as levels of other minerals. The female iguanas from tourist areas differed significantly in ionized calcium.
Among both males and females from tourist areas there was a 100 percent endoparasitic infection rate and tourist-fed iguanas also displayed atypical loose faeces.
“Both sexes on visited islands consume food distributed by tourists, although male iguanas are more aggressive when feeding and eat more provisioned food,” Knapp said. “Consequently, they may be more impacted by provisioning with unnatural foods, which could explain the greater suite of significant physiological differences in males between populations.
“The biological effects of altered biochemical concentrations may not be manifested over a short time period, but could have deleterious effects on long-term fitness and population stability,” Knapp said.
The researchers acknowledged that increased population density as a result of tourist-feeding can be beneficial for endangered species, but warned that unnaturally high densities and excessive reliance on tourists for food may prove problematic if food supplementation is discontinued for any reason. Further, plant community dynamics can be disrupted by changed feeding patterns in the iguanas.
“The complete restriction of feeding by tourists may not be a realistic option. Instead, wildlife managers could approach manufacturers of pelleted iguana foods and request specially-formulated food to mitigate the impact of unhealthy food,” Knapp said. “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.
“We also endorse a broad education campaign and discourage references to feeding iguanas on advertisements. We urge serious discussions among wildlife managers and stakeholders to identify tactics that mitigate the impacts of current tourism practices without compromising an important economic activity,” he added.
Bahamian rock iguana is among the world’s most endangered lizards due to habitat loss, introduced mammals, illegal hunting, threats related to increased tourism, and smuggling for the illicit pet trade. They are listed on the IUCN Red List of Threatened Species.