|by Marcia Malory|
A tree frog, or arboreal frog, is a frog that spends most of its life living in trees.
Tree frogs are usually very small, because the branches and twigs of trees must support their weight.
A tree frog usually has long legs and long toes that it can use to grasp branches. Its toes often have pads that are covered with sticky secretions.
Often, tree frogs will have green backs with lighter-colored undersides.
Some tree frogs can change color from green to brown, so they can camouflage themselves against both green tree leaves and brown tree bark.
Tropical tree frogs are sometimes brightly colored.
A tree frog may have bright colors on its inner thighs. When it jumps from a tree branch in order to avoid a predator, these bright colors are revealed. This distorts the frog's shape, which makes it difficult for the predator to spot it.
Bright coloration on animal that is only seen when that animal is trying to escape from a predator is known as flash coloration.
Tree frogs usually eat arthropods, such as insects and spiders. Larger tree frogs may eat small vertebrates, such as other small frogs.
Many tree frogs have loud mating calls.
Some tree frogs are flying frogs - they have skin flaps on their arms and legs that allow them to glide from tree to tree.
A tree frog may belong to one of two different families - Rhacophoridae and Hylidae.
The Rhacophoridae are sometimes known as Old World tree frogs, because they can be found only in the tropics of Asia and Africa. They are also sometimes known as bush frogs, shrub frogs or moss frogs.
The Hylidae are native to North America, Central America and South America, Europe, Australia and Asia. They are sometimes known as true tree frogs, to distinguish them from the Rhacophoridae.
Sometimes, the Hylidae are called New World tree frogs, although they live in both the New World and the Old World.
Although the Rhacophoridae and the Hylidae are only distantly related, they have very similar physical characteristics because they have evolved to live in very similar habitats.
Their physical similarities are the result of convergent evolution, which occurs when organisms that are not closely related develop similar physical adaptations because they must survive in similar conditions.
Not all members of the Hylidae and Rhacophoridae live in trees today. Some have adapted to life in grasslands or in deserts, for example.
Like all amphibians, tree frogs must begin their lives in moist environment.
Some tree frogs lay their eggs in ponds or streams and fertilize them there.
Others lay their eggs on leaves that hang over streams or ponds, so the tadpoles drop into the water as soon as they hatch.
Still other species lay their eggs in treeholes that have become filled with water.
Some tree frogs lay their eggs in plants that hold water, such as a type of bromeliad that is known as tank-epiphyte.
A tank-epiphyte has broad leaves that are pressed together to form a "tank" that can hold water.
Some species of Hylidae that live in Central and South America are marsupial frogs.
A female belonging to one of these species lays her eggs in leaf litter.
A male then places the eggs in a brood pouch that is on the female's back.
He fertilizes the eggs when they are in the pouch.
The eggs stay in the pouch until they hatch.
The female then drops the newly hatched tadpoles into water.