WASHINGTON Many salamander species in Mexico and Guatemala have suffered dramatic population declines since the 1970s, driven to the brink probably by a warming climate and other factors, U.S. scientists said on Monday.
The salamanders' fate provides the latest evidence of striking losses among the world's amphibians, a phenomenon some experts see as a harbinger of doom for many types of animals.
Biologist David Wake of the University of California Berkeley and colleagues tracked about two dozen species of salamanders at several sites in Guatemala and southern Mexico.
They put a special emphasis on the San Marcos region of Guatemala, boasting one of the most thoroughly studied and diverse salamander populations in the tropics.
Compared to levels measured in the 1970s, the population of half of the species in the two countries declined markedly. Four species were apparently completely gone and a fifth virtually wiped out, Wake said.
The cause is probably a complex combination of factors including climate change -- with warming temperatures forcing salamanders to higher and less hospitable elevations -- as well as habitat destruction and a fungal disease, Wake said.
"We have documented what has long been feared -- that tropical salamanders are being hit hard by something and are disappearing," Wake, whose findings appear in the journal Proceedings of the National Academy of Sciences, said in a telephone interview.
The species that formerly were the most common were the ones hit the hardest, Wake said.
Many scientists worry that climate change will have a terrible impact on animal populations, with those in the most sensitive places, like polar bears in the Arctic, hit first.
Some experts view today's amphibians, whose ancestors were the first land vertebrates, as sort of a canary in the coal mine, warning of future disaster for the animal kingdom.
"If we are convinced there is something going wrong and these are canaries in the coal mine, what are you going to do about it? This is a problem," Wake said. "One major avenue is global climate change. That is clearly a factor."
While not included in this study, Wake said similar losses are occurring in salamanders in Costa Rica.
A lot of the research into amphibian losses had focused on frogs. This study adds valuable data on salamanders.
The various species in this study ranged from about 1.5 inches to 5 inches long. Ground-dwelling salamanders were found to be the hardest hit, as opposed to those living in trees and other types of vegetation.
(Writing and reporting by Will Dunham; Editing by Bill Trott)
The Pentagon releases photographs linked to allegations of abuse of detainees in Iraq and Afghanistan.