As in tropical forests all round the Equator, the trees of the Neotropical ecozone are full of numerous kinds of animals. They support many more different types of animal than the trees of the forests in the temperate or cold zones. With the constant high temperatures and the daily rainfall, vegetation flourishes and several hundred different species of tree thrive in a very small area. A thick canopy consisting of intermeshed boughs of the tallest trees spreads out to catch the sunlight. Epiphytes and dangling creepers festoon these high branches. As a result, there are many different kinds of leaves, flowers and fruits available above the gloom and roots of the forest floor. Many varieties of animals have evolved to exploit these potential foodstuffs. Generally, the tree-living animals of South America are smaller than those of the tropical forests in the rest of the world. The airy canopy is alive with little arbrosaurs adapted to feed on the thousands upon thousands of different types of insects that make their homes there.
Some of the arbrosaurs, however, have abandoned their insectivorous way of life and have evolved into totally new forms. The nectar-sucking gimp, for instance, is a tiny animal, no more than 20 centimeters (8 inches) long including the slender delicate head, and eats nothing but nectar. Its snout has evolved into a long tube which acts as a rigid sheath for an extendable nectar-gathering tongue. These features are similar to those of the ant-eating adaptation of the pangaloon, and it is obvious that both animals evolved from the same group of arbrosaurs that crossed from North America during the Great American Interchange in the Pliocene. The tubular snout may be seen as an example of preadaptation where a feature evolves spontaneously and is then retained because it is perfectly suited for a particular purpose.