BIG ON FIGS: In Indonesia, one nutritious fruit is the wild fuel that runs the rain forest - figs, a favorite food of animals in the rainforest, have a high calcium content

The sun has barely risen over the sea, but its hot rays are already bathing the steamy forests of Tangkoko Nature Reserve on Sulawesi Island in Indonesia. The morning is heralded by a cacophony of wild calls and screeches in the forest canopy above me. It seems every animal in this small reserve is converging on an enormous fig tree. I have been watching this tree for weeks, and now its entire burden of fruit-between 400,000 and 600,000 figs-is ripening all at once. The bounty attracts birds and mammals from all directions to partake in a feeding frenzy.

But why, in a forest that harbors hundreds of different types of fruiting trees, is this fig so irresistible to so many forest creatures? This is the question I came here to answer.

I have been fascinated with figs ever since my first encounter with them as a five-year-old dissecting Fig Newtons in my parents' Kentucky kitchen. Back then I was delighted with the flavor of the gooey paste squeezed between soft pastry and intrigued by tiny seeds that peppered the dark brown fillings. Now, some three decades later, I'm still captivated by figs, but this time as an ecologist with the Wildlife Conservation Society, studying the role of figs in rain forest ecosystems.

I knew that if I could figure out why figs are irresistible to the denizens of Sulawesi's forests, I could shed some light on why so many other tropical animals around the globe also relish them. Figs are consumed by everything from tiny ants to 2-ton elephants. Our closest relatives, chimpanzees, crave them. Even a bear cuscus, a woolly marsupial found in Sulawesi's forests and normally a leaf-eater, won't turn down a succulent fig.

I wondered if this wide appeal is simply due to the abundance and diversity of fig trees. There are more than 600 species of figs in the Tropics, making them the second-largest group of woody plants in the world. Many of these are in the Indo-Malay region. Sulawesi (also known as Celebes), an island in the middle of the Indonesian archipelago, alone boasts more than 100 species. The island's figs grow in locations as diverse as rocky shores, mountain tops and even the cracks in older buildings in the provincial capital of Manado.

Tangkoko Nature Reserve is the perfect place to study figs. In my 1,000-acre research area, there are about 37 species of fig trees with a density of about 5 trees per acre-the highest fig density recorded in a Southeast Asian forest. Despite the profusion, it's not difficult to tell the figs apart. Some species look like a typical tree, with a single trunk growing from earthbound roots. Others, known as strangling figs, look more like a confusing maze of roots and tendrils than a real tree.

The fruits span the spectrum from creamy white to blue black, and range in size from tiny pearls to golf balls. (Technically, these aren't really fruits, but a collection of inverted flowers surrounded by a fleshy, bulbous structure with a tiny hole in the end.) Some sit on thin pedestals or dangle from the tips of twigs; others perch directly on branches, lined up like kernels on a corncob. Some even droop from branches in graceful clusters stretching more than 2 yards. My favorites protrude like cauliflower heads directly from trunks.

Strangling figs are the most abundant fig trees in Tangkoko and the easiest to differentiate from other trees. They have an upside-down approach to life, beginning as seeds deposited high in the canopy by a bird or monkey. The seeds germinate in nooks and crannies of other trees and send delicate root tendrils downward. Once the roots reach the ground, they develop into woody, ropelike structures that begin to surround the host, and slowly fuse and harden. As a strangling fig grows, it takes on the appearance of a coil of ropes, binding its host in a tight, and sometimes deadly, embrace. The host tree's bark is often crushed and critical fluid supplies are cut off by the fig's deadly hug. In time, some figs-like the one I'm standing under-become free-standing trees with an internal framework mirroring the form of the long-dead host.

Above my head the noise level escalates to that of a New York City intersection at rush hour. Scores of sleek, black mynas, an assortment of tubby, green fruit pigeons, a few tiny parrots hanging upside-down and a legion of stately red-knobbed hornbills pummel me with discarded bits of cherry red figs.

While these raucous animals busily gulp down the fruits, I begin my day's work. Scanning the tree's half acre of branches with my binoculars, I estimate about half the fruits are still green-so the site promises to be even more chaotic in a few days when the entire canopy is ripe. I troop on to investigate the fruiting status of the other 155 fig trees that are part of my regular monthly round.

From my studies, I know that the presentation, color and size of fig fruits influence which animals feed on what, and when. Fruits displayed on the tips of branches are available primarily to small birds-the flowerpeckers, mynas and delicate, hovering sunbirds that can feed on the wing. Heavy-bodied hornbills and monkeys can only feed on these figs if they can reach them from a safe seat in the canopy. Figs that grow on trunks tend to be snatched by large, dog-faced fruit bats that might have trouble negotiating the web of branches and twigs in the canopy. Fruits close to the ground are gobbled by babirusas (forest pigs), deer and other earth-bound animals.