Only a few vertebrate animals other than birds live in the thin branches of the tropical rainforest's tallest trees.

It is very difficult to move around in this environment, and those that do usually spend some time in the rainforest's lower layers.

The animals that can be found in the emergent trees are generally small and light, in keeping with the fragile branches.

Proboscis Monkey

An exception to this rule is the proboscis monkey, which can found among the mangrove swamp forests of Borneo. Here, the emergent trees are firm and rigid and do not grow to enormous heights.

The proboscis monkey, Nasalis larvatus, is a sturdy animal-a male weighs up to 50 pounds (22kg)- and lives in groups of one or two adult males, two to five females and several young.

The troop roams through the swamps feeding on mangrove shoots and the young leaves of the pedada tree as well as fruits and flowers.

For much of the day the monkeys apparently sunbathe up in the emergent trees. At night, they seek the safety of the treetops to avoid predators such as their main enemy, clouded leopard.

Proboscis monkeys are remarkably agile. They have long tails of up to 30 inches (76cm) but use them only as counterbalances. With the aid of long fingers and toes, they run along branches or swing from one to another.

They will launch themselves across a gap in the trees using a supple branch as a springboard. Landing safely depends on the accurate integration of hand and foot, but, if surprised or startled in the treetops, a proboscis monkey may drop 20 feet on to a sturdy branch.

Proboscis monkeys are believed to be territorial. Males have large, pendulous noses and are very vocal.

As the monkey makes its hard "honking" noise, the long nose straightens out. Females can make the honking noise, but are usually quieter than males. The monkeys mate in the trees at any time of the year, and give birth to a single offspring. Even birth takes place up in the trees.

Feathertail Glider

The feathertail, or pygmy, glider, Acrobates pulchellus, lives among the emergent trees of the New Guinea tropical rainforest. This nocturnal marsupial is related to the greater and sugar gliders of Australia.

The feathertail glider has evolved physical characteristics that allow it to glide from tree to tree.

It has a flap of skin, known as a patagium, strung between the front and rear limbs. The animal extends its limbs, and thus the skin flaps, which gives it sufficient lift to glide smoothly forward and downward.

The tail, which is fringed with stiff hairs and strongly resembles a feather, provides directional stability. The tail's light structure is essential for these tiny creatures-adult males are about 3 inches (7.5 cm) long. A furry tail would be too heavy.

Feathertail gliders feed on insects, and the nectar and flower buds of the tallest forest trees.

Although they sometimes descend to the lower levels of the tropical rainforest, when they are on the forest floor they are very vulnerable to predators. They are safest among the treetops.