Volume 0, Issue 1, Winter 1983

Can Rain Forests Survive Without Bats?

By Tuttle, Merlin D.

Loss of rain forests is one of the most serious environmental problems of the 1980's. Major conservation strategies already are being planned. Yet few, if any, decision makers understand the extent to which these forests depend on bats for their surv ival.

In tropical ecosystems, bats often comprise more than half of all mammal species, and their biomass may in some places equal that of all other mammals combined. Nevertheless, most species have never been studied, and major ecosystem studies have faile d to acknowledge that bats even exist. Such neglect can have serious consequences.

In tropical rain forests and savannahs, bats are the most important seed dispersing animals. In fact, one recent West African study showed bats to be far more effective than birds. Bats also are the primary pollinators of numerous tropical plants. M ore than 130 genera of trees and shrubs already are known to rely on bats for pollination, and many more such relationships await discovery.

We are only beginning to understand the importance of such bats, but already their ecological and economic impact on rain forests is obvious. Recent studies demonstrate that seed dispersal activities of bats can be critical to reforestation of clear-c ut areas, and that many of the tropics' most economically important plants depend on bats for propagation.

The nearly endless list of valuable products from these plants includes many grocery store fruits such as peaches, bananas and avocados as well as kapok and hemp fibers for surgical bandages, life preservers and rope, latex for chewing gum, prized lumb er for furniture and crafts, beads for jewelry, carob for candy and even Tequila liquor.

Many plants of economic importance continue to depend on bats. For example, regional harvests of Durian fruit in Southeast Asia and Iroko timber in West Africa each amount to annual sales of close to 100 million dollars. The former requires bats for pollination and the latter for seed dispersal. Even for plants, such as bananas, that now are vegetatively reproduced on plantations, maintenance of genetic strains of wild progenitors could someday prove critical to development of new, more productive o r disease resistant varieties. Man is far from outgrowing his long dependence upon bats.

Despite the obvious value of bats, tens of thousands of bat caves and other roosts have been poisoned, blown up or bulldozed shut, killing millions of beneficial bats and destroying entire cave ecosystems.

Vampire Bats of Latin America have harmed livestock, but ill-advised attempts to control them often have led to the destruction of millions of highly beneficial bats instead. In the Old World, exaggerated reports of crop damage from fruit bats also ha ve led to killing of bats. Farmers are alarmed by the sight of large bats eating fruit that ripens prematurely or that is missed during picking. Because fruit bats prefer strong-smelling, ripe fruits, commercial crops that are picked green for shipping are seldom damaged. Birds and rats are not so picky, leaving their depredations to be blamed on the more conspicuous bats. As a consequence, large colonies of big flying fox bats are being destroyed.

Some African countries are right now investigating possible means of poisoning huge colonies of the Straw-colored Fruit Bat (Eidolon helvum), simply because a few trees in certain traditional roosting sites are damaged. Single colonies may cont ain a million or more of these bats that consume more than a half million pounds of fruit and nectar nightly from native rain forest and savannah trees. Imagine their cumulative impact on pollination and seed dispersal!

Some investigators now suspect that seasonal movements of these bats, over thousands of kilometers, have led to overestimates of their numbers. It is possible that fewer than two dozen great colonies exist. These are highly vulnerable, and killing in one country could have serious ecological consequences in another country a thousand kilometers away.

Even where bats are valued as sources of food and fertilizer, they often are not safe. Throughout much of the Old World and the South Pacific Islands, bats are considered a delicacy and are over harvested for human food, folk medicine and even aphrodi siacs. Many populations of large flying fox bats are seriously threatened. On Guam, bat dinners may sell for $25 a plate, and in West Africa bats are so valuable that two poachers working together can make $1,000 in a single day.

Much loss of tropical bats results from simple human ignorance. In Southeast Asia and elsewhere, some of the largest bat colonies are destroyed by poorly planned limestone quarrying. In both Thailand and Malaya huge colonies of the important Cave-dwel ling Nectar-eating Bat (Eonycteris spelaea) are in immediate danger. In Thailand, for example, the Rakong Cave, containing one of the country's largest bat colonies, may be lost by the time you read this.

In many cases the most important question is not extinction, but how many bats can we afford to lose before their pollination and seed dispersal activities become inadequate to preserve the balance of rain forest ecosystems? What will happen, for exam ple, if huge colonies of Straw colored Fruit Bats cease to perform their annual migrations across the vast expanses of Africa, servicing countless thousands of rain forest trees nightly?

Can rain forests survive without bats? Hopefully, prompt action to save large but vulnerable bat populations, not just already rare species, will avoid the ultimate and possibly disastrous test.



This Dwarf Epauletted Bat (Micropteropus pusillus) is one of several bat species that, according to Dr. Don Thomas, plays a critical role in maintenance of forest diversity and in regeneration of disturbed areas in West Africa.

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