The unique marine iguanas of the Galapagos islands have been devastated by the aftermath of an oil spill, scientists say, losing almost two thirds of their number on one island since a tanker ran aground in January last year.
Writing in today's Nature, the scientists say that the high mortality rate in the wake of what was seen as a minor accident suggests that wildlife is more vulnerable to oil spills than previously thought.
Sixty-two per cent of the marine iguana population on Santa Fe have died in the year since the tanker Jessica ran aground on San Cristobal, another part of the archipelago, on January 17 2001.
The tanker spilled about 3m litres of diesel and bunker oil after the accident, but strong currents dispersed most of the slick, so few marine animals were directly affected.
By the time the remnants of the slick reached Santa Fe, it was reduced to one litre of oil being washed ashore for every metre of beach, a level considered low by international standards.
Yet the team reporting in Nature, led by the Princeton University biologist Martin Wikelski, said it was hard to explain the sudden decline of iguanas by other means.
Before the spill, Mr Wikelski and his colleagues spent years studying marine iguanas on Santa Fe and Genovesa, an island to the north.
After the spill, which did not affect Genovesa, there was no mass deaths of iguanas there.
One of the most likely reasons for the iguanas' suffering, Mr Wikelski theorises, is that the animals depend on specialised bacteria in their stomachs which break down the marine algae they feed on.
Even if the iguanas themselves are not vulnerable to low levels of oil contamination, the bacteria may be.
"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," the scientists say.
The marine iguanas of the Galapagos are the world's only seagoing lizards. There are thought to be between 200,000 and 300,000 on the islands.
Charles Darwin, whose voyage to the Galapagos helped shape his speculation about the origins of species, noted the ubiquity of the iguanas, and what he saw as their ill-favoured appearance.
He wrote: "It is a hideous-looking creature, of a dirty black colour, stupid, and sluggish in its movements."
Writing in today's Nature, the scientists say that the high mortality rate in the wake of what was seen as a minor accident suggests that wildlife is more vulnerable to oil spills than previously thought.
Sixty-two per cent of the marine iguana population on Santa Fe have died in the year since the tanker Jessica ran aground on San Cristobal, another part of the archipelago, on January 17 2001.
The tanker spilled about 3m litres of diesel and bunker oil after the accident, but strong currents dispersed most of the slick, so few marine animals were directly affected.
By the time the remnants of the slick reached Santa Fe, it was reduced to one litre of oil being washed ashore for every metre of beach, a level considered low by international standards.
Yet the team reporting in Nature, led by the Princeton University biologist Martin Wikelski, said it was hard to explain the sudden decline of iguanas by other means.
Before the spill, Mr Wikelski and his colleagues spent years studying marine iguanas on Santa Fe and Genovesa, an island to the north.
After the spill, which did not affect Genovesa, there was no mass deaths of iguanas there.
One of the most likely reasons for the iguanas' suffering, Mr Wikelski theorises, is that the animals depend on specialised bacteria in their stomachs which break down the marine algae they feed on.
Even if the iguanas themselves are not vulnerable to low levels of oil contamination, the bacteria may be.
"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," the scientists say.
The marine iguanas of the Galapagos are the world's only seagoing lizards. There are thought to be between 200,000 and 300,000 on the islands.
Charles Darwin, whose voyage to the Galapagos helped shape his speculation about the origins of species, noted the ubiquity of the iguanas, and what he saw as their ill-favoured appearance.
He wrote: "It is a hideous-looking creature, of a dirty black colour, stupid, and sluggish in its movements."
