Low-level oil spill kills Galapagos iguanas - study
Date: 07-Jun-02
Country: UK
Author: Patricia Reaney
Within a year of the accident, 62 percent of iguanas on the nearby island of Santa Fe were dead, proving that even a low-level spill can cause serious damage.
"It is quite devastating. At the wrong time it could have totally wiped out this population," Martin Wikelski, an eco-physiologist at Princeton University in New Jersey, told Reuters.
If it had happened when food supplies were not as abundant as they were, all the island's iguanas could have disappeared.
Most of the 800,000 gallons of oil that spewed from the tanker was dispersed by strong ocean currents, sparing the world's rarest sea creatures and birds which inhabit the islands west of Ecuador's coast in the Pacific Ocean.
But by carefully monitoring the number of iguanas before and after the accident, Wikelski and his colleagues discovered that enough trace oil remained to kill more than half of the iguanas on Santa Fe.
"Despite the reportedly low degree of oil contamination, several lines of evidence indicate that the pronounced increase in mortality that we observed among the Santa Fe animals was related to the oil spill," they said in a report in the science journal Nature.
Wikelski described the findings as a warning against complacency over low-impact contamination after an environmental accident in wildlife areas.
Adult iguanas on Santa Fe and the more distant island of Genovesa, where none was harmed by the spill, are free of predators and normally die from lack of food or old age.
But there was no lack of algae, which they feed on, and the scientists found large numbers of skeletons along the shores of the island, suggesting the spill was linked to the deaths.
The number of iguanas also declined steeply over a short period of time.
They suspect the oil may have had a toxic effect on the iguanas, on the seaweed they eat, or they may have refused to eat because the algae was contaminated.
Another possible explanation is that traces of oil killed micro-organisms in the animals that are needed to help them digest the algae.
Whatever the cause, the scientists said their findings illustrate the damage low-level pollution can cause to wildlife, particularly on islands such as the Galapagos which so many rare, exotic species consider home.
"Our findings warn against complacency over apparently low-impact contamination after environmental disasters in other wildlife areas, such as the Arctic National Wildlife Refuge in Alaska," Wikelski said.
