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Australian Green Tree Frog

2007 Schools Wikipedia Selection. Related subjects: Insects, Reptiles and
Fish

                iWhite's tree frog

                             Conservation status

   Least Concern (LC)
            Scientific classification

   Kingdom: Animalia
   Phylum:  Chordata
   Class:   Amphibia
   Order:   Anura
   Family:  Hylidae
   Genus:   Litoria
   Species: L. caerulea

                                Binomial name

   Litoria caerulea
   ( White, 1790)

   The Australian Green Tree Frog, simply Green Tree Frog in Australia,
   White's Tree Frog, or Dumpy Tree Frog (Litoria caerulea) is a species
   of tree frog native to Australia and New Guinea, with introduced
   populations in New Zealand and the United States. The species belongs
   to the genus Litoria. It is physiologically similar to some species of
   the genus, particularly the Magnificent Tree Frog (Litoria splendida)
   and the Giant Tree Frog (Litoria infrafrenata).

   The Green Tree Frog is a large species compared with most Australian
   frogs, reaching 10 centimetres in length. The average lifespan of the
   frog in captivity, about sixteen years, is long in comparison with most
   frogs. Green Tree Frogs are docile and well suited to living near human
   dwellings. They are often found on windows or inside houses, eating
   insects drawn by the light.

   Due to its physical and behavioural traits, the Green Tree Frog has
   become one of the most recognisable frogs in its region, and is a
   popular exotic pet throughout the world. The skin secretions of the
   frog have antibacterial and antiviral properties that may prove useful
   in pharmaceutical preparations.

Taxonomy

   Original print of the Green Tree Frog, published in John White's "A
   Journal of a Voyage to New South Wales". Artist: S. Stone
   Enlarge
   Original print of the Green Tree Frog, published in John White's "A
   Journal of a Voyage to New South Wales". Artist: S. Stone

   The common name of the species, "White's Tree Frog", is in honour of
   the first person to describe the species, John White. The Green Tree
   Frog was the first Australian frog scientifically classified. The
   species was originally called the "blue frog" (Rana caerulea); although
   the Green Tree Frog is green, the original specimens White sent to
   England were damaged by the preservative and appeared blue. This is
   because 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 same. The frog is
   also known more simply as the "Green Tree Frog." However, that name is
   often given to the most common large green tree frog in a region, for
   example, the American green tree frog (Hyla cinerea).

   The Green Tree Frog is sometimes confused with the Magnificent Tree
   Frog (Litoria splendida), which inhabits only north-western Australia
   and can be distinguished by the presence of large parotoids and rostral
   glands on the head. The Giant Tree Frog (Litoria infrafrenata) is also
   sometimes confused with the Green Tree Frog. The main difference is a
   distinct white stripe along the edge of the lower jaw of the Giant Tree
   Frog, which is not present in the Green Tree Frog.

Distribution

   Distribution of Litoria caerulea (in black) on the Australian
   continent.
   Enlarge
   Distribution of Litoria caerulea (in black) on the Australian
   continent.

   The Green Tree Frog is native to northern and eastern regions of
   Australia and to southern New Guinea. Distribution is limited mostly to
   areas with a warm, wet tropical climate. Eastern Australia, although
   cool in winter, also hosts the species. It is found in the southern
   Australian state of Victoria, but the frog cannot survive southern
   Victoria's cold winters and is therefore restricted to the north. In
   New Guinea, the Green Tree Frog is restricted to the drier, southern
   region. Its range spans from Irian Jaya to Port Moresby, and is most
   abundant on Daru Island. There have been isolated records in northern
   New Guinea, however this is thought to have been through introduction
   by humans.

   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 in Florida, and it is unknown whether
   they have caused any ecological damage as an invasive species. In New
   Zealand, a population was once present; however, there have been no
   sightings since the 1950s.

Physical description

   The Green Tree Frog can grow up to 10 centimetres (4 inches) in length.
   Its colour depends on the temperature and colour of the environment,
   ranging from brown to green; the ventral surface is white. The frog
   occasionally has small, white, irregularly shaped spots on its back, up
   to five millimetres in diameter, which increase in number with age. The
   frog has large discs at the end of its toes, of about five millimetres
   in diameter at maturity. These help the frogs grip while climbing and
   allow them to climb vertically on glass. The eyes are golden and have
   horizontal irises, typical of the Litoria genus. The fingers are about
   one-third webbed, and the toes nearly three-quarters webbed. The
   tympanum (a skin membrane similar to an eardrum) is visible.

   The tadpole's appearance changes throughout its development. The length
   of the species' tadpoles ranges from 8.1 millimetres (once hatched) to
   44 millimetres. They are initially mottled with brown, which increases
   in pigmentation (to green or brown) during development. The underside
   begins dark and then lightens, eventually to white in adults. The eggs
   are brown, in a clear jelly and are 1.1–1.4 millimetres in diameter.

   Although frogs have lungs, they absorb oxygen through their skin, and
   for this to occur efficiently, the skin must be moist. A disadvantage
   of moist skin is that pathogens can thrive on it, increasing the chance
   of infection. To counteract this, frogs secrete peptides that destroy
   these pathogens. The skin secretion from the Green Tree Frog contains
   caerins, a group of peptides with antibacterial and antiviral
   properties. It also contains caerulins, which have the same
   physiological effects as CCK-8, a digestive hormone and hunger
   suppressant. Several peptides from the skin secretions of the Green
   Tree Frog have been found to destroy HIV without harming healthy
   T-cells.
   The left frog is the White-lipped Tree Frog, note the white stripe
   along the jaw. The center is the Green Tree Frog. The right is the
   Magnificent Tree Frog, note the large parotoid glands present above the
   tympanum.
   Enlarge
   The left frog is the White-lipped Tree Frog, note the white stripe
   along the jaw. The centre is the Green Tree Frog. The right is the
   Magnificent Tree Frog, note the large parotoid glands present above the
   tympanum.

Ecology and behaviour

   A Green Tree Frog caught in a spider's web after eating the spider. The
   frog survived.
   Enlarge
   A Green Tree Frog caught in a spider's web after eating the spider. The
   frog survived.

   Green Tree Frogs are very docile. They are nocturnal and come out in
   early evenings to call (in spring and summer) and hunt at night. During
   the day they find cool, dark, and moist areas to sleep. During winter,
   Green Tree Frogs do not call and are not usually seen.

   Depending on their location, Green Tree Frogs occupy various habitats.
   Typically, they are found in the canopy of trees near a still-water
   source. However, they can survive in swamps (among the reeds) or in
   grasslands in cooler climates. Green Tree Frogs are well known for
   inhabiting water sources inside houses, such as sinks or toilets. They
   can also be found on windows eating insects. They will occupy tanks (
   cisterns), downpipes (downspouts), and gutters, as these have a high
   humidity and are usually cooler than the external environment. The
   frogs are drawn to downpipes and tanks during mating season, as the
   fixtures amplify their call.

   The species' call is a low, slow crawk-crawk-crawk, repeated many
   times. For most of the year, they call from high positions, such as
   trees and gutters. During mating season the frogs descend, although
   remaining slightly elevated, and call close to still-water sources,
   whether temporary or permanent. Like many frogs, Green Tree Frogs call
   not only to attract a mate. They have been observed calling to
   advertise their location outside the mating season, usually after rain,
   for reasons that are uncertain to researchers. They will emit a stress
   call whenever they are in danger, such as when predators are close or
   when a person steps on a log in which a frog resides.

   The species' diet consists mainly of insects and spiders, but can
   include smaller frogs and even small mammals. Frog teeth are not suited
   to cutting up prey, so the prey must fit inside the mouth of the frog.
   Many frogs propel their sticky tongues at prey. The prey sticks, and is
   consumed. Green Tree Frog will use this technique for smaller prey;
   however for larger prey, it pounces, then forces the prey into its
   mouth with its hands.

   The frog has few native predators, among them snakes and a few species
   of lizards and birds. Since the European settlement of Australia,
   non-native predators have been introduced, primarily dogs and cats. The
   species has an average life expectancy in captivity of sixteen years,
   but some have been known to live for over twenty years, which is long
   for a frog. The average life expectancy in the wild is lower than in
   captivity, due to predation.

Reproduction

   A brown and green Green Tree Frog.
   Enlarge
   A brown and green Green Tree Frog.

   Prior to the mating season in late spring to summer, the male Green
   Tree Frog develops a black nuptial pad on the inner surface of the
   thumb. This aids amplexus by allowing the male to continue a grip on
   its mate for the duration of amplexus. The male calls (individually) to
   attract a female, and the two typically meet at a still-water source.

   During amplexus, the male mounts the female. The female then expels her
   eggs at such a speed that the sperm is forced into the egg. A large
   spawn of about 200 to 300 eggs is left in the water, approximately a
   half metre from the frogs. The eggs sink and attach themselves to
   submerged objects. The two frogs can remain in amplexus for about two
   days, during which the process is repeated many times, resulting in the
   laying of an average of 2000 to 3000 eggs. An egg hatches three days
   after its laying. The water must be 28–38 degrees Celsius and
   5–50 centimetres deep for the eggs and tadpoles to survive.
   Metamorphosis takes between two and three months, and sexual maturation
   about two years.

Conservation status

   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. Much of the Green Tree Frog's
   natural habitat has been destroyed. Also, some of the frogs have been
   found infected with chytrid fungus (causing chytridiomycosis). These
   two factors associated with the general decline in frog populations in
   Australia threaten to reduce the population of the Green Tree Frog.
   However, because of the long life expectancy of this species, any
   effects of a reduced reproduction rate will take longer to spot than
   they would in a species with a shorter life expectancy.

As a pet

   The Green Tree Frog is one of the most popular pet frogs throughout the
   world. Its docile nature, often cartoon-like appearance, and long life
   expectancy make it an attractive choice for exotic-pet owners. It is
   also one of the easier frogs to care for: their diet is broad and they
   have 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 will deposit fat layers over the top of the head and body,
   giving it a "dumpy" appearance.
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   with only minor checks and changes (see www.wikipedia.org for details
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