In the green world, tree frogs come in a very wide variety, with differences of appearance, habitat and specificity. They live either on soil or in water and while most of them are green, there are many sub-species that have a duller color. Small insects and small invertebrates are the primary source of food for these tiny animals. Spread all over the northern hemisphere from America to Asia, tree frogs are known to become noisy when there are signs of rain in the atmosphere, and in certain cultures people used to rely on them for weather forecast.
Gray tree frogs are mostly spread in the United States and Canada, they are very small and their maion categorization name is North American common tree frog. As the name implies they are predominately gray, but the color intensity varies from dark to lighter grays. They never grow beyond four or five centimeters in length (less than two inches) and they present a lumpy texture on their skin. For a common person many tree frogs may look the same despite the fact that they may belong to different species. For example Cope's Gray frog looks exactly like the gray one but has a different call.
Gray tree frogs can be found from central Texas to northern Canada, and though they inhabit the entire North America they have never been encountered in other places of the world. Regarding their behavior, gray tree frogs are primarily arboreal, they like forest areas that are close to water; thus after rains they can be seen near small pools in the forest. They use night time for cover and feeding when they hunt for small insects (like arthropods). Mating happens in the spring and summer months, and it is during this season that their skin color changes from green to gray as a camouflage meant to protect them from predators.
Gray tree frogs can also be found in captivity as many pet shops sell them. They adapt well in captivity requiring only some living plants and a permanent water source as the ambient habitat. Food can be purchased from pet shops so there is no problem about keeping them. As most other frog species, they are moderately sensible to pollution, pH fluctuations and UV-B radiations so they show health issues gradually, yet, the highest vulnerability of tree frogs is that to environmental changes. Make sure you know everything about how to look after such animals in captivity, or they'll die!