White's Tree Frog

The Australian green tree frog is a member of the family Hylidae and is placed in the subfamily Pelodryadinae, which is endemic to Australia and New Guinea and includes over 100 species in the genera Ranoidea and Nyctimystes. The common name of the species, "White's tree frog", is in honour of John White's first description in 1790. The green tree frog was the first Australian frog to be scientifically described; the original specimen found its way into the collection of Sir Joseph Banks, but was destroyed when the Hunterian Museum in London was bombed in World War II. The species was originally called the "blue frog" (Rana caerulea) despite its green colour. The specimens White sent to England were damaged by the preservative and appeared blue. The colour of the frog is caused by blue and green pigments covered in a yellow layer; the preservative destroyed the yellow layer and left the frog with a blue appearance. The specific epithet, caerulea, which is Latin for blue, has remained.

The green tree frog is native to northern and eastern regions of Australia and to the lowlands of New Guinea. Distribution is limited mostly to areas with warm, wet tropical climates. Its range spans from Irian Jaya to Port Moresby, and is most abundant on Daru Island. The IUCN suggests "scattered locations" in both New Guinea and Indonesia. The species has been introduced to both the United States and New Zealand. In the United States, it is restricted to two regions within Florida, where it was possibly introduced through the pet trade. Only small populations have been found there, and whether they have caused any ecological damage as an invasive species is unknown. In New Zealand, several individuals were liberated in various locations in 1897 and 1899, and a further accidental introduction was made in the 1940s. No sightings have been reported of this species since the 1950s. Depending on their location, green tree frogs occupy various habitats. They prefer moist forests but are not strictly limited to tropical rainforests. Green tree frogs are little troubled by the presence of humans and often live in close association with them. They sometimes stray inside houses and are found in such places as sinks and toilets. They can also be found on outside windowsills at night, eating insects attracted to the light, and they may gather under outdoor lighting for the same reason. They sometimes occupy tanks (cisterns), downpipes (downspouts), and gutters, as these have high humidity and are usually cooler than the external environment. They may be drawn to the downpipes and tanks during the mating season because the fixtures amplify their calls. Green tree frogs seem to have homing abilities, being able to return to locations from which they were caught from a considerable distance after being displaced.

after eating the spider]] Australian green tree frogs are very docile and unafraid of humans.) among their prey. The species has an average life expectancy in captivity of 16 years, but some have been known to live over 20 years.

Breeding occurs between November and February. During the mating season, the males call from slightly elevated positions close to the still-water sources in which they choose to breed. Clumps of between 200 and 2000 eggs are laid which initially float, but sink within 24 hours. The development of the tadpoles takes about six weeks, after which they undergo metamorphosis and leave the water as juvenile frogs.

The green tree frog is one of the most popular pet frogs throughout the world. Its docile nature and long life expectancy make it an attractive choice for exotic pet owners. It is also one of the easier frogs to maintain; its diet is broad and it has a strong resistance to disease. One problem commonly associated with keeping this species as a pet is overfeeding; green tree frogs tend to become obese if overfed. In the wild, exertion of energy is required for a frog to capture its prey. However, in captivity, they are usually given live feed in a confined space. This lessens the activity needed for feeding, resulting in weight gain. An overweight member of the species deposits fat layers over the top of the head and body, giving it a "dumpy" appearance, thus the name "dumpy tree frog". The rover fireflies of the genus Photinus (including the common eastern firefly of North America) are poisonous to these frogs, and an incident has been reported in which a firefly was fed to a green tree frog, which subsequently died.

Australian law gives protected status to the green tree frog—along with all Australian fauna—under the federal Environment Protection and Biodiversity Conservation Act 1999. The International Union for Conservation of Nature lists the green tree frog's conservation status as being of "least concern", given its broad range, its large total population, and its tolerance of a variety of habitat types. The population trend seems to be stable, and any decline in numbers is not likely to be at a fast enough rate to justify listing it in a more threatened category. In suburban areas, this frog is threatened by pollution and by predation by domestic animals. Also, some of the frogs have been found to be infected with the chytrid fungus which causes the fatal amphibian disease chytridiomycosis. The frog's status in New Guinea is poorly studied, but in 2002, some 75,000 individuals were exported from Indonesia as part of the pet trade, and this may impact populations in some locations. The frog is present in a number of protected areas in New Guinea, and it has been successfully bred in some Australian zoos. Overall, the main threat to this species is the potential for a widespread disease epidemic.

Although frogs have lungs, they absorb oxygen through their skin; for this to occur efficiently, the skin must be moist. A disadvantage of moist skin is that pathogens such as molds and bacteria can thrive on it, increasing the chance of infection. To counteract this, frogs secrete peptides that destroy these pathogens. The secretion from the paratoid gland of the green tree frog contains 25 caerins, a group of peptides with antibacterial and antiviral properties. The caerins produced by frogs of this species from different geographical localities have subtle but reproducible differences. The secretions also contain caeruleins, which have the same physiological effects as CCK-8, a digestive hormone and hunger suppressant. These caeruleins now have a number of clinical applications. The fungus Batrachochytrium dendrobatidis, the causal agent of chytridiomycosis, is causing declines in many species of amphibians, but the secretions produced by the green tree frog and certain other Australian species of frog (Litoria chloris and Litoria genimaculata) are protective against this fungus. The peptides inhibit the growth of the fungus in vitro and these frog species are believed not to be in decline. Green tree frogs are sometimes used as model animals in research. The structure of their toe pads was used to investigate the microstructure and properties of the epithelium that allows the animals to adhere to wet surfaces.