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 ForestFocus on Indonesia: Page 6 Other rare and declining inhabitants of Asia's rainforests play important roles in pollination. Many trees that produce important commercial products need to be pollinated by wild animals. An extremely valuable fruit is the Durian, which is almost unknown outside southeast Asia. In spite of a rank odor emanating from the outer fruit, the yellow core inside the rind is considered a great delicacy, worth more than $90 million a year in markets throughout Indonesia and Malaysia. What is less well known is the dependence of the Durian tree on a particular species of bat to pollinate it. The Cave Fruit Bat (Eonycteris spelaea) is the sole pollinator of these valuable trees, pollinating the flowers while feeding on the nectar of the flowering fruit. Yet this bat is unprotected from the persecution, hunting for food and destruction of its limestone caves that are causing its decline. The number of threatened bat species native to Asia has increased dramatically in recent years, according to the IUCN (Hilton-Taylor 2000). Throughout these rainforests, bats are disappearing, some before their ecological role was known.
Hundreds of tropical plants and trees have evolved for pollination by bats. Most flowers of such trees are found in the canopy, giving easy access to the nectar‑feeding and fruit bats, either hanging on long stems, set clear of the surrounding foliage, or clustered on branch tips near twigs where bats can land (Mitchell 1986). These bat flowers open only at night, with odors quite unlike the day‑blooming flowers that attract insects and birds; instead, they are musky and sour, which seem to attract the bats (Mitchell 1986). Evolved with shapes that conform to the muzzle of the bat in order to deposit pollen on the bat's face, some flowers have large, trumpet‑like openings that almost engulf the bat's head. Others are brush‑like with masses of stamens rich in pollen, while still others have numerous small flowers in a ball‑like inflorescence producing both nectar and pollen (Mitchell 1986).
The trees that have evolved to be pollinated by bats, some even by a particular species of bat, while providing food for the bats, represent a classic example of mutual dependency. Current logging practices and the killing of many of these bats for food, or destruction of their caves, endanger both trees and bats. Many of Indonesia's threatened bats are fruit bats, and a large number are found only in Indonesia. The Pygmy Fruit Bat (Aethalops alecto), for example, is found only on Borneo; the Small‑toothed Fruit Bat (Neopteryx frosti) is native to Sulawesi; the Javan Tail‑less Fruit Bat (Megaerops kusnotoi) is restricted to Java; four others are confined to the island of New Guinea. Half of Borneo's 140 mammal species are bats, and more than 50 of these feed primarily on insects (Yates 1992), another major benefit of these poorly understood mammals.
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