Gold tree frog
| Gold tree frog | ||||||||||||
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Golden tree frog ( Litoria aurea ) |
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| Ranoidea aurea | ||||||||||||
| ( Lesson , 1827) |
The golden tree frog ( Ranoidea aurea , synonym : Litoria aurea ), also known as the golden tree frog , is a species from the family Pelodryadidae that is native to eastern Australia . When fully grown, it reaches a size of about 11 cm, making it one of the largest native frogs in Australia. Ranoidea aurea belongs to the Ranoidea aurea complex , which also includes Ranoidea moorei , Ranoidea raniformis , Ranoidea dahlii and Ranoidea cyclorhynchus .
Taxonomy
The golden tree frog has several physical and behavioral characteristics that can be ascribed to the real frogs (Ranidae). Because of this, it was previously divided into the Ranidae family. These include the pointed muzzle, the long legs and the pronounced webbed toes; the middle ear stands out due to its size, and the body shape is largely the same as that of the Ranidae. Another argument in favor of the classification is that the golden tree frog, like the species of Ranidae, prefer to live near water and therefore seldom cover long stretches of land if sufficient humidification is not guaranteed. The reason for the downgrading were anatomical differences to the real frogs. The animal's bone and cartilage structure is more closely related to the species in the family, so it is now classified as a member of the Pelodryadidae , which is related to the tree frogs .
René-Primevère Lesson first described the golden tree frog as Rana aurea . Since then it has been reclassified about 20 times and received the current name Litoria aurea 37 years after the first classification by Albert Günther (whereas after nine reclassifications, the same name was reverted to).
distribution
The home of the golden tree frog is southeastern Australia. Formerly distributed from Brunswick Heads in north New South Wales to East Gippsland in Victoria and west of Bathurst , Tumut and the Australian capital territory, today's populations can be found in a comparatively restricted territory. Today the frog's range only extends from Byron Bay to East Gippsland, and it is mainly found in coastal areas. Experts estimate the difference between the former and today's distribution area to be at least 90%.
However, the animal can be found both in Sydney and on two islands on the east coast, namely Broughton Island and Bowen Island. It also exists in New Zealand and on the Pacific islands of New Caledonia and Vanuatu .
features
Gold tree frogs are large and powerfully built frogs, when fully grown they can reach body sizes of around 4.5 to 11 cm in length. On average, however, they grow to between 6 and 8 cm; and they are among the largest specimens of frogs on the Australian continent.
The males are usually smaller and less stocky than the females and it can be observed that the color of the back is very variable in both. Shades of green (dark green to emerald), green-bronze, copper or even gold have already been documented. It is noticeable that in cooler times the colors begin to get darker, sometimes even to an almost black shade.
A beige or pale yellow stripe arises behind the eye, which is delimited with gold at the top and black at the bottom; it runs on the side of the body between the middle ear and the groin. Another stripe lies between the eye and the shoulder. The underside of the abdomen shows a beige or white, relatively coarse pattern structure. The color of the legs varies between green and bronze, the inner thigh is colored blue-green up to the groin. In male gold tree frogs, a yellowish shade can be seen on the vocal sac .
The frog's pupil is horizontal and slit, the iris, on the other hand, is golden brown and a black streak runs between the pupil edges and those of the eye. In addition to a distinctive and egg-shaped middle ear, the animal also has large suction cups on its toes, which are used as a climbing aid. The fingers are free, but the toes are completely webbed, which is due to a largely water-related life. During the mating season, oestrus calluses also develop on the thumbs , with which the female is held during mating.
Way of life and reproduction
Like all tree frogs, the golden tree frog spends a considerable amount of the day warming up in the sun on rocks or blades of grass. What is unusual is that it is also diurnal; When touched, a pungent smelling mucus is secreted, which acts as a broad spectrum antibiotic and even works against cancer, which helps the frog to fight off dangerous microorganisms and pathogens.
Usually the frog can be found in coastal swamp areas and forests, but populations have also been found in former industrial regions. Therefore, it is difficult to determine what demands it really makes on its habitat, since it can also be found in all kinds of waters, with the exception of fast-flowing rivers. Most often, however, it is found in temporary pools of water that are shallow and free of debris; he avoids waters with predatory fish in them. Lake or ponds with tall vegetation, especially reeds, which serve as sun spots for the animal, are preferred; in winter, places are sought that are just as suitable as shelter and for raising the young. There are usually grasses or fields around the habitat that prove to be suitable for foraging.
The reproduction depends very much on the salinity and temperature of the water. The salt content has an impact on the development of the tadpoles , and the place is only suitable as a breeding site from a temperature of around 20 ° C. Gold tree frogs can cope with salinities of 0.6% without any effects, but from a salinity of 0.8% the mortality rate increases and the growth rate decreases. The animal benefits from a minimum salt content of around 0.1-0.2%, as it kills pathogens (such as the Chytridiomycota ).
When fully grown, the frogs develop a very wide range of foods, they also devour other frogs (sometimes they even become cannibals ); the tadpoles feed on suspended matter , algae and bacteria . Natural enemies are water birds and snakes , turtles , eels , fish and invertebrates pose a threat to tadpoles .
The breeding season for golden tree frogs is in the warm months between October and March. During this time, the males use their vocal sacs to make a mating call as they float in the water. This call is a deep, multi-part grumble that is often described as similar to switching a motorcycle (a close relative of the golden tree frog, the motorcycle frog Litoria moorei , was even named for its mating call ). An average of 5,000 eggs are laid during spawning , and a pile of 11,682 has been documented. Initially the spawning mass floats, but if there is a disturbance or after 12 hours it sinks to the bottom. The larvae hatch after 2–3 days and change from a tadpole to a finished frog after 2–11 months. The time depends on the water temperature and the food available. Spawning is more likely to happen in waters that are free of predatory fish and of short-lived nature.
The tadpoles are very large, specimens up to 8 cm in length have been spotted, but smaller tadpoles are far more common. The body shape is usually the same width as it is high, the fin is yellowish and conspicuously arched. The musculature, on the other hand, is poor and tapers towards the end, like the fin. The body itself is translucent yellow and shows darker areas above the belly. Shortly before the development of limbs, the greenish color of the adult appears. These intermediate forms of individual development then resemble adults and now measure an average of 2.6 cm.
Danger
In the past decade, the numbers of wild golden tree frogs have declined by almost a third. The following factors are held responsible for this decline: the destruction of the habitat, the introduction of predatory fish and the reconstruction and expansion of sewage systems. The declines are also closely related to the introduction of the goblin carp , a predatory fish from North America that was introduced into the ecosystem as part of the malaria containment (the fish feeds on mosquito larvae). According to laboratory studies, the tadpole populations show extreme sensitivity to this species of fish when they enter their habitat as hunters. In addition to the danger from predatory fish, the dangers from non-native mammals, such as B. cats or foxes , changes in water quality, herbicide use and the destruction of woodland are all major factors in the decimation of the species. However, since the species is able to survive in destroyed and polluted environments, deforestation is a major factor and pollution are probably not the main causes of endangerment. Fungi such as the chytrid fungus are seen as the main cause of the decline in the population of the golden tree frog after observing the species during the 1970s and 1980s.
For some time now, the frog has been involved in research and study projects in order to find ways to preserve the species permanently. A good part of this research is also focused on controlling the predatory fish threat. Others, in turn, strive to find new, suitable habitats or to maintain old ones accordingly so that a species-appropriate life can be guaranteed. Projects have also been started to draw public attention to the problem and to find support from this side.
Pet ownership
Gold tree frogs are also often kept as pets . They are also suitable for owners who are less familiar with amphibians, as they are relatively easy to care for and do not display aggressive behavior. When keeping an enclosure, a habitat should be chosen that offers it bathing, hiding and climbing opportunities, and plants should not be dispensed with either. The frog feels at home with a relative humidity of 60–80% and temperatures of 24–28 ° C during the day and 18–22 ° C at night. Commercially available insects and small mice are good food.
literature
- GH Pyke (Ed.): The green and golden bell frog Litoria aurea: biology and conservation. Royal Zoological Society of New South Wales. Mosman, 1996
- Harold G. Cogger: Reptiles & Amphibians of Australia. 2nd, revised edition. AH & AW Reed Pty Ltd, London 1979, ISBN 978-0-5890-7176-9 .
- MJ Tyler: Australian Frogs - A Natural History. Reed Books 1994, ISBN 0-7301-0468-0 .
Web links
- Litoria aurea in the endangered Red List species the IUCN 2004 Posted by: Jean-Marc Hero, Graeme Gillespie, Harold Cogger, Frank Lemckert, Peter Robertson, 2004. Accessed April 2, 2018th
- Litoria aurea on Google Images
- Litoria aurea and other Australian frogs on frogs.org
- Synonyms of Litoria aurea