Rain forests are large, high-humidity forests that generally average more than 100 inches of rain per year. These giant forests account for a large portion of the earth's oxygen, as well as plant and animal life. There are several layers to the rain forest, categorised as the emergent layer, upper canopy, lower canopy (or understory) and forest floor. The understory basically consists of the lowest level of trees---trees that grow to an average of 20 feet in height---and small shrubs and bushes. There are quite a number of animals---even some that have yet to be discovered---that make their home in the lower canopy of the rain forest.
Insects are by far the most numerous and varied of the animal life in the rain forest understory, comprising more than 90 per cent of the animal species. According to Mongabay, "a single bush in the Amazon may have more species of ants than the entire British Isles." In fact, there are so many insects, it is almost impossible to make any kind of conclusive statement about any particular population of insects within the rain forests' lower canopy. In addition to a variety of ant species, there are many species of butterflies, like the brilliantly-coloured morpho butterfly; leaf and stick insects, also called walking sticks; beetles, like the conspicuous rhinoceros beetle; mosquitoes; dragonflies; moths; crickets; grasshoppers; wasps; bees; and---though not truly insects---spiders, including the second-largest spider in the world, the Goliath bird-eater tarantula.
There are many monkeys and other primates that live throughout the rain forest. However, there are a number of these rain forest primates that spend much, if not all, of their time in the understory. Some of these species include the capuchin monkey, loris and long-tailed macaque.
Reptiles and Amphibians
There are numerous species of snakes, lizards and tree frogs that inhabit the understory of the rain forest. Some notable frog species include the glass frog, the red-eyed tree frog and the deadly poison dart (or poison arrow) frog. Some of the more common understory lizards include various species of iguanas, chameleons and geckos. Most lower-canopy snakes are various species of nonvenomous boa constrictors. However, there are some venomous snake species found throughout the understory, like the deadly poisonous eyelash viper.
There are a number of large and small cat species that can be found throughout the various rain forests of the world. However, due to a variety of factors---mostly involving habitat loss and overhunting by humans---many of them are either threatened or endangered. While cats in the rain forest spend a fair amount of time on the forest floor, nearly all of them have become specialised tree hunters, spending much of their life in the lower canopy. The largest rain forest cat species is the tiger; other rain forest big cats include the jaguar, leopard and puma (or mountain lion). Some of the smaller wildcats that spend much of their time in the rain forest understory are the margay, leopard cat (different than the leopard) and ocelot.
While the majority of rain forest birds inhabit the upper canopy and emergent trees, there is still a diverse bird population, mostly insectivores, that specialise in understory living. Various species of peafowl (peacocks and peahens), wrens and thrushes are just some of the birds that thrive in the rain forest lower canopy.