Global mystery: Why are snakes dying off?

Climate change is a possible explanation for the snake's 'drastic decline' in Europe and Africa. Snakes now join a list of declining animal populations that includes fish, amphibians, reptiles, birds, and mammals.

Gernot Vogel/World Wildlife Fund/AP
Dendrelaphis kopsteini, shown in this undated photo, a snake that has a bright orange, almost flame-like, neck coloration that gradually fuses into an extraordinary iridescent and vivid blue, green and brown pattern, discovered in Borneo. A recent study shows the world's snake population is declining in Europe and Africa.

Good news for Indiana Jones and others with ophidiophobia: a new study shows snake populations have declined worldwide.

Bad news for farmers and those afraid of rats and mice: rodents now have fewer predators to outsmart.

The world's first global study on snake populations revealed that 11 of 17 snake populations in the United Kingdom, France, Italy, and Nigeria plummeted between 1998 to 2002. Some populations fell by as much as 90 percent, according to the study from the Centre for Ecology & Hydrology in England.

"Since the drastic decline, the populations have not continued to decline, they have not died out, they are still present, but they are present at much lower densities than before," lead scientist Chris Reading says in a telephone interview from England.

Only one population (the Western whip snake of France) showed a sign of increasing during that four-year-period. (The Guardian provides a complete list of snakes in the study.)

"I don’t think people realize how important snakes are," says Mr. Reading. "They are the top predator in many ecosystems in which they occur. If you get rid of a top predator, it will have a knock-on affect on all those species on which they prey... You take out the predator and suddenly you have an increase in the pest species." Pests, such as rats, feed on rice and wheat, and already a major hazard to crops in Africa and Asia.

The reason for the snake decline is not entirely clear, says Reading. It could be because of diminished food supply or an altered habitat. The affected populations were in both protected and non-protected environments, and the study's wide geographic range, from the foggy coast England to the desert of Nigeria, may show something happening on a global scale.

Climate change? Maybe

"Perhaps the climate may have had some bearing on this," he says.

Notably, the snake populations studied all give birth to live young (other species like pythons, lay eggs) and are sit-and-wait predators, making them more vulnerable to change in their environments.

But climate change should not be the assumed cause, Reading says. Frogs and other amphibians, for example, have been dying off in large numbers since 1989 because of a deadly fungus called Batrachochytrium dendrobatidis. And a combination of oil spills, oil-and-gas development, and climate change has left nearly a third of the US's 800 bird species endangered, threatened, or in significant decline.

Reading hopes the study, published on June 9 in the journal Biology Letters, will urge other scientists worldwide to monitor their snake populations, too.

"It’s just to flag up what we think is happening," he says. "It’s possible that we have an aberration, but I don’t think so. I think we have something important happening here."

There are an estimated 3,000 snake species worldwide. The snake now joins a list of declining populations of animals, including fish, amphibians, reptiles, birds, and mammals.

“We are currently witnessing the greatest extinction crisis since dinosaurs disappeared from our planet 65 million years ago,” according to the International Union for Conservation of Nature.

(Editor's note: The original article incorrectly stated the name of the fungus that causes the disease chytridiomycosis.)


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