Meet the Gray Tree Frogs at Wildwood Zoo!
We have three gray tree frogs in our collection at the zoo that we received from a private breeder in October 2019. As they are still quite young, it is very difficult to sex them but will become easier as they mature.
As the scientific name implies, gray tree frogs are variable in color owing to their ability to camouflage themselves from gray to green, depending on the substrate where they are sitting. The degree of mottling varies. They can change from nearly black to nearly white. They change color at a slower rate than a chameleon. One aspect that is unique to this frog appearance is that its legs feature a dark bandish pattern which then contrasts sharply with the bright yellow or orange under the sides of its legs. Dead gray tree frogs and ones in unnatural surroundings are predominantly gray. The female does not call and has a white throat; however, the male does call and can show a black/gray/brown throat during the breeding season. The female is usually larger than the male. It is important to know when trying to identify this frog that the appearance at a younger age is similar to others of the same tree frog, but as the frog increases in age, the appearance varies. They are relatively small compared to other North American frog species, typically attaining no more than 1.5 to 2 inches. Their skin has a lumpy texture to it, giving them a warty appearance. These frogs rarely ever descend from high treetops except for breeding. They are strictly nocturnal.
Gray tree frogs inhabit a wide range, and can be found in most of the eastern half of the United States, as far west as central Texas and Oklahoma. They also range into Canada in the provinces of Quebec, Ontario, and Manitoba, with an isolated population in New Brunswick.
The gray tree frog is most common in forested areas, as it is highly arboreal. Its calls are often heard in rural residential areas of the East Coast and the Midwest. It prefers to breed in semi-permanent woodland ponds without fish, but it also lays eggs in swamps, vernal pools, man-made fountains and water gardens, and even in rainwater-filled swimming pool covers.
A male begins the mating call in early spring, shortly after emerging from hibernation. In the mid-range areas males begin calling in late April to early May. Males call to females from trees and bushes that are usually close to, or overhanging, streams or standing water.
The exact timing of breeding for gray tree frogs varies based on temperature and their location throughout the range. Most reproduction takes place early on, although the calling season lasts from late April to early August. Individuals may mate up to three times in a season.
Males are very territorial and will fight other males to defend their area. Fights may last 30 to 90 seconds and consist of wrestling, shoving, kicking and head butting until the subordinate male retreats. Females instigate mating by approaching a calling male and touching him before rotating 90 degrees. The individuals engage in amplexus, a mating position in which the male grasps the female with his front legs, as the female deposits 1,000 to 2,000 eggs which are externally fertilized by the male. Since mating occurs while the frogs are floating in water, eggs are deposited into the water in small clusters, which attach themselves to structures via a transparent, mucous outer layer.
Tadpoles usually hatch after three to seven days, depending on the water temperature. About 10 minutes to an hour before hatching, the embryo has to release a fluid to help break down the wall of the egg. Tadpole development depends on water temperature with metamorphosis typically occurring in 45 to 65 days. They become sexually mature after two years.
Adult gray tree frogs mainly prey upon different types of insects and their own larvae. Mites, spiders, plant lice, snails and slugs are common prey. They may also occasionally eat smaller frogs, including other tree frogs. They are nocturnal and hunt in the understory of wooded areas in trees and shrubs. As tadpoles, they eat algae and organic detritus found in the water.