Farmers who slaughter fruit bats because they consider them to be pests may suffer still greater losses in production because the bats cross-pollinate their fruit trees. The 180 or so species of fruit bats are threatened throughout the world's tropical and temperate zones by pest eradication schemes, hunting for game and deforestation.
Two species of Pteropus bat from Micronesia in the Pacific are already thought to be extinct and a growing number are endangered.
Concern over the plight of bats that feed on fruit and nectar has been heightened by mounting evidence for their crucial role in pollinating and dispersing the seeds of more than 500 species of plants and trees. These include banana, mango, guava, kapok and sisal, plus varieties of cactus, mangrove and valuable hardwood trees. Such plants have evolved to be pollinated by bats. Their blossoms produce large amounts of nectar during the night.
The Chiroptera Specialist Group - a branch of the Species Survival Commission of the International Union for Conservation of Nature and Natural Resources - has just launched an action plan to protect Pteropus.
As part of the intensified research effort, a zoological expedition from the University of East Anglia is monitoring populations of bats in the Comoros Islands in the Indian Ocean. Paul Racey, of the department of zoology at the University of Aberdeen, chairs the specialist group. He expects the report to propose the designation of roosting sites as nature reserves and to recommend laws that forbid dealers from selling bats for food.
On the American-run Pacific island of Guam, fruit bats are a traditional delicacy. Pteropus tokudae has been hunted to extinction, and islanders now import frozen bats from neighbouring Micronesia islands as well as from Papua New Guinea and Queensland, Australia. This state, under pressure from farmers, recently declared four species of fruit bats as vermin.
"Pteropus is a big genus," says Tim Inskipp of the Convention on International Trade in Endangered Species, "and many of the 70 species are under threat." Political intricacies, stemming from the fact that not all Pacific islands are party to the convention, have frustrated the efforts of conservationists. Traders sidestep restrictions by re-exporting bat carcasses for human consumption through third countries.
There are still many healthy colonies of fruit bats around the world. Fruit farmers commonly regard them as pests, but the bats prefer to eat ripe fruit while farmers usually harvest fruit before it ripens.
In the US, the Federal Register reported recently that "the loss of fruit bats threatens the future of the entire southwestern desert ecosystem". Earlier studies had shown that bats are important pollinators. They transfer pollen and cross fertilise plants. In the absence of bat pollination, seed production by century plants (the Agave cactus) dropped by a factor of 3000 according to a study by Merlyn Tuttle, the director of Bat Conservation International, a group based in Texas. "About 20 species of giant cacti in the [US] south-west are heavily dependent on bat pollination," Tuttle says.
The Agave cactus, which is used in the production of the drinks, tequila and mezcal, is pollinated by bats that feed on its nectar. One depends on the other so if one declines, both suffer.
"It's a vicious spiral," says Tony Hutson of the Flora and Fauna Preservation Society in Britain. Hutson believes that, by curtailing the pollination of wild fruit by killing bats, fruit farmers are putting their own prosperity at risk.
DATE: November 1988
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