Study: Snakes in 'Alarming' Decline on Three Continents

(June 9) -- A sharp decline in snake populations on three continents might strike some as a bit of a blessing. But to the scientists who spent over two decades studying the data, the findings are "alarming" -- and they're not entirely sure why it's happening.

According to published accounts of the study, 11 of 17 snake populations in Britain, France, Italy, Nigeria and Australia showed an abrupt drop-off over a four-year period starting in the late 1990s.

"Two-thirds of the monitored populations collapsed, and none have shown any sign of recovery over nearly a decade since the crash," the authors reported today in Britain's Royal Society journal Biology Letters. "Unfortunately, there is no reason to expect a reversal of this trend."

An abrupt decline began to occur around 1998, and the project leader, Chris Reading of the U.K.'s Centre for Ecology and Hydrology, told BBC News "we don't have a clue" why.

Climate change, however, could have been a main contributor, because strong El Nino conditions helped make 1998 the "warmest year on record," according to the National Oceanic and Atmospheric Administration.

The study suspects that the sharp drop has been caused by a loss of habitat and prey, and that all the immediate threats have climate change as their common cause, The Guardian of London reports. But the study stresses there is no proof of what's causing the decline, the paper adds.

Snakes are the top predator of pests like rats and mice in habitats such as rice paddies, and their decline could lead to wider consequences, the scientists suggest. Those dropping in numbers -- some by more than 90 percent -- include the asp and the smooth snake from Europe, the Gabon viper and rhinoceros viper from West Africa, and the royal python.

"All the declines occurred during the same relatively short period of time and over a wide geographical area that included temperate, Mediterranean and tropical climates," the authors wrote. "We suggest that, for these reasons alone, there is likely to be a common cause at the root of the declines and that this indicates a more widespread phenomenon."

The snake populations were tracked between 1987 and 2009 using regular surveys, from reports on a daily basis over several months of the year to monitoring roadkill.

Reading told the BBC, "This is the first time that data has been analyzed in this way, and what we've shown is that in different parts of the world we seem to have this steep decline in a short period. It surprised us when we realized what we were looking at."

Reading appealed to other researchers to come forward if they have more long-term data.

"The purpose of this paper was to say, 'This is what we found,' and to say to other herpetologists, 'Now go and look at your own data,''' he told the BBC. "But I think that with so many populations in different places showing decline, it's more than coincidence."