New help for threatened bats

Bats are key parts of many ecosystems

By BBC News Online's environment correspondent Alex Kirby

Scientists say almost half the world's bat species face some degree of threat to their survival.

They say bat populations in many countries are experiencing alarming declines, and have launched a plan to help them.

Many species are valuable for controlling insect numbers, and are useful in other ways to farmers. And some are known to science from a few museum exhibits, with scarcely any more data available.

The conservation plan was devised by IUCN-The World Conservation Union, and launched at a bat research conference in Kuala Lumpur, Malaysia.

It covers the 834 species of what are known as microbats, most of them insect eaters. Nine years ago, IUCN launched a similar plan for the 167 other species, the old world fruit bats.

The two groups together make up almost a quarter of all known mammals. About 22% of bat species are considered threatened, and a further 23% are near-threatened.

Winning allies

Bats are highly vulnerable to extinction: they reproduce slowly, with most species producing only one offspring a year.

A key part of the scientists' plan is to improve people's understanding of bats and to dispel misconceptions about them.

Bats seldom threaten humans
Image: US Fish and Wildlife Service

The smallest mammal in the world is the bumblebee bat of Thailand, which weighs just two grams.

By contrast, some of Indonesia's flying foxes have wingspans of almost 1.75 metres (six feet).

The scientists stress that bats do not become entangled in people's hair, and seldom transmit disease to humans, or to other animals.

Like all mammals, they can catch rabies, though less than 0.5% of bats do so. And even they, according to IUCN, normally bite only in self-defence and pose little threat to people who do not handle them.

But when bats decline there may be repercussions across a whole ecosystem.

Flying pest-killers

In Bracken Cave, in Texas, US, 20 million Mexican free-tail bats eat roughly 200 tonnes of insects every night. A single little brown bat can catch 1,200 mosquito-sized insects in an hour.

So declines in bat numbers can increase demand for chemical pesticides, with consequences for other species.

Cave roosts are often threatened
Image: USFWS/Craig Stihler

Tropical bats pollinate flowers and disperse seeds in rain forests, while desert plants rely on nectar-feeding bats as primary pollinators.

And agricultural plants, including bananas, breadfruit, mangoes, cashews, dates and figs also need bats for pollination and seed dispersal.

IUCN says there are several key bat areas. The diversity in central and northern south America far exceeds anywhere in the eastern hemisphere, though there are important areas there as well.

They are in east Africa, peninsular Malaysia, the Indonesian island of Sulawesi, and in a band stretching from Nepal and north-east India to south China.

Dr Abigail Entwistle is a bat specialist at Fauna and Flora International, based in Cambridge, UK.

New species

She told BBC News Online: "It's a problem here - the mouse-eared bat became extinct in the UK three or four years ago, and the greater horseshoe bat has declined to about 10% of its historical range.

"The problem with bats is that they're very difficult to study. We know less than 10% of the thousand species in any detail.

"We hope people will take more interest in some of the rarer species, and develop some generic conservation approaches that could help all bats.

"Almost certainly, there are new bats waiting to be discovered. It's only two years since we found that the pipistrelles are two distinct species, on the basis of their echolocation frequencies."