Bat specimens dating back more than 50 years may help scientists understand high rates of a killer disease on a Pacific island.
Islanders suffered from a degenerative disease
Guam is known for incredibly high rates of a degenerative disease which has some of the hallmarks of motor neuron, Parkinson's and dementia, but cannot be firmly identified as any of them.
Among the Chamorro people on the island, rates of the mysterious condition run at between 50 and 100 times the "normal" rate of motor neuron disease found in other communities.
Many theories have been put forward as to the cause of the disease, but the mystery has yet to be solved.
In recent years, some researchers have suggested that islanders habit of catching and eating a type of bat called a flying fox may be to blame.
It is suggested that the flying foxes feed on seed containing a chemical highly toxic to human brain cells.
When residents ate the animals, high levels of the chemical, which had accumulated in the bat tissues, was passed on.
The flying fox is now an endangered species in Guam, but researchers from the Institute of Ethnobiology in Kauai, Hawaii, analysed bat skins preserved at the Museum of Vertebrate Biology at the University of California at Berkeley.
They measured the concentration of BMAA - the neurotoxic chemical they suspect is behind the illness.
All of the skins contained a high concentration of BMAA, and researchers believe it backs up the theory that bat consumption may be to blame.
The bats, they think, ate large quantities of the seeds, and the poison accumulated in their bodies without killing them.
Dr Paul Cox, one of the researchers, said: "The concentration of BMAA in these 50-year-old museum specimens suggests that the Chamorro people may have unwittingly ingested high doses of BMAA when they ate flying foxes.
"This appears to be the consequence of biomagnification of the toxic substances in the food chain."
A separate academic, Dr Carmel Armon of the Department of Neurology at Loma Linda School of Medicine in California, welcomed the research.
However, he said it was possible that the museum's flying fox collection might not be representative of flying foxes in general on Guam.
Rates of the mystery illness are now declining alongside a decline in the bat population - only a small colony of the animals still exists on the island.