The Juan Fernández fur seal, once thought extinct, can ingest toxic metal without ill effects - though no one knows how.
A playful creature that mankind came very close to wiping out now offers hope that we may be able to find ways to tackle one of the most pernicious environmental poisons, say scientists. Their research shows that one of the world’s most isolated aquatic mammals, Arctocephalus philippii, can tolerate high levels of cadmium, as well as other metallic pollutants, without suffering ill effects.
A. philippii is the second smallest species of fur seal (second only to the Galápagos fur seal) and lives only on the Juan Fernández archipelago and one or two nearby islands in the Pacific Ocean, hundreds of miles off the coast of Chile. It was here that sailor Alexander Selkirk was marooned from 1704 to 1709, an experience that was fictionalised by Daniel Defoe in Robinson Crusoe after whom the archipelago’s main island is now named.
Fortunately, the Juan Fernandez fur seal’s story is one of success (albeit only after the collapse of the fur seal pelt trade), says Oceana.org. And it's only recently that scientists began studying them in detail - making a startling discovery. “We collected samples of their faeces and found they contained extremely high levels of cadmium and other elements such as mercury,” said Constanza Toro-Valdivieso of Cambridge University’s conservation research institute. “The discovery was very surprising,” she said. “Cadmium is poisonous to mammals but somehow these seals were processing it and passing it through their digestive systems and seem to be suffering little harm in the process.”
“The discovery that these animals appear to tolerate high levels of cadmium in their bodies has important medical implications, and it is very important for us to find out exactly how the Juan Fernández seal achieves this,” said Toro-Valdivieso. “It could be something to do with the animal’s genes or something else completely. It is an issue that we are hoping to follow up over the coming years. These animals have a lot to tell us.”