Australian Green Tree Frog

Australian green tree frog（圖片來源：Tnarg 12345，採用 CC BY-SA 3.0 授權）

The Australian green tree frog (Ranoidea caerulea or Litoria caerulea), also known as the White's tree frog or dumpy tree frog, is native to northern and eastern Australia as well as lowland regions of New Guinea. It has also been introduced to Florida in the United States and New Zealand, although the population in New Zealand has been eradicated. In the wild, it inhabits warm and humid tropical climates, with a distribution ranging from West Papua in Indonesia to Port Moresby in Papua New Guinea. In Australia, its range extends from the Kimberley region of Western Australia across the Northern Territory and Queensland to northern New South Wales and northeastern South Australia, covering more than 4 million square kilometers.

This species is larger than most native Australian frogs, with adults reaching 10 to 11.5 cm in length. Females are slightly larger than males. The body is robust and rounded, with a distinctive fatty ridge above the eyes. The dorsal coloration varies depending on environmental conditions and temperature, ranging from brownish green and gray-green to bright emerald green, sometimes with irregular white spots. The toe pads are large and well-developed for climbing. The fingers have approximately one-third webbing, while the toes have about three-quarters webbing. The ventral surface is rough and creamy white. Males possess a gray, wrinkled vocal sac on the throat, whereas females have a white throat.

In the wild, they are commonly found in moist forests, canopy layers, and areas near water bodies, although they can survive for extended periods in terrestrial environments away from water, such as tree hollows in eucalyptus forests or grasslands. They adapt well to human environments and are frequently encountered in residential areas, often hiding in sinks, toilets, pipes, water tanks, or window sills. At night, they gather around lights to feed on insects attracted to illumination. This species also demonstrates homing ability and can return to its original habitat after being displaced over considerable distances.

Australian green tree frogs are nocturnal, becoming active at dusk and during the night for feeding and calling, while resting in cool, moist, and shaded locations during the day. Although they are not strictly rainforest species, they utilize water collected on leaves or in crevices to maintain hydration. Their skin secretes a waxy layer that reduces water loss. During dry conditions, they retreat into cool refuges or burrow into soil, forming a cocoon-like structure using shed skin and mucus to prevent dehydration. When threatened, they may emit a loud scream to startle predators, and produce short squeaking sounds when handled.

Their diet in the wild consists mainly of insects, including moths, cockroaches, grasshoppers, and spiders. They may also consume smaller frogs and even small mammals such as bats. Small prey are captured using a sticky tongue, while larger prey are seized directly and pushed into the mouth using the forelimbs. Natural predators include snakes, birds, and introduced animals such as dogs and cats. Their lifespan in the wild is relatively short, but in captivity they can live on average 16 years, with some individuals exceeding 25 years.

The breeding season occurs from November to February in the Southern Hemisphere. Males call from elevated positions near still water to attract females, producing a deep, slow "brawk-brawk-brawk" call repeated multiple times. Each clutch contains approximately 200 to 2000 eggs, which initially float and then sink within 24 hours. After hatching, the tadpoles require about six weeks to undergo metamorphosis into froglets and leave the water.

Housing Requirements in Captivity

Australian green tree frogs are arboreal and require vertical space for climbing. A tall glass or acrylic enclosure is recommended, with a secure and well-ventilated mesh lid that is resistant to rust and sharp edges. For 3 to 4 adult frogs, a minimum enclosure size of 45 x 45 x 60 cm is appropriate. For a single individual, at least 35 x 35 x 50 cm is required, with height prioritized over width.

The enclosure should include live or artificial plants, branches, and vertical structures for climbing, as well as hiding spots and shaded areas to reduce stress. Suitable substrates include moist sphagnum moss or large stones. Avoid small gravel or wood chips that may be accidentally ingested and cause intestinal blockage. The substrate should remain moist but not waterlogged, and partial cleaning and replacement should be performed regularly.

A temperature gradient is essential. During the day, the warm area should be maintained at 28 to 30°C, while the cooler area should range between 22 and 24°C. At night, temperatures may drop slightly but should not fall below 18°C. Temperatures below 10°C can be fatal. During colder seasons, heating pads or heat lamps should be used in combination with a thermostat to prevent overheating. The water area can be maintained at 24 to 26°C using an aquarium heater.

Humidity should be maintained between 50% and 70%. Light misting once daily is sufficient, using dechlorinated water rather than untreated tap water. Prolonged excessive humidity should be avoided to prevent fungal and bacterial growth. The enclosure should be kept out of direct sunlight and provided with 10 to 12 hours of low-intensity UVB lighting (2.0 UVB is sufficient) to support normal physiological functions.

The water area should include safe access points to prevent small froglets from being trapped by surface tension. Water quality should be maintained through partial water changes, replacing 20% to 50% weekly. With a filtration system, this interval can be extended to two weeks.

Feeding Conditions

Australian green tree frogs are opportunistic carnivores, primarily feeding on live insects in the wild, with occasional predation on other small animals. In captivity, they should be provided with live prey such as crickets, cockroaches, mealworms, moths, superworms (high in fat and should be given sparingly), snails, and earthworms. Some keepers offer pinky mice or other high-protein items, but excessive long-term feeding of such prey may lead to kidney disease and should only be done occasionally.

At least one out of every 2 to 3 feedings should involve dusting all prey items with calcium powder and multivitamin supplements to prevent metabolic bone disease. A mixing ratio of approximately 1:1 for calcium and vitamin powder is recommended.

Feeding frequency depends on age. Juveniles should be fed daily, while subadults and adults should be fed 2 to 3 times per week, with a total weekly intake of approximately 10% to 20% of body weight. Prey size should not exceed the width of the frog's mouth to prevent choking. Dead insects should be removed promptly to avoid contamination.

Feeding is best conducted in the evening or at night due to their nocturnal behavior. Live prey can be released into the enclosure or offered individually using feeding tongs for better intake monitoring.

Breeding Conditions

Successful captive breeding requires simulation of natural conditions:

• Environmental adjustments: Mimic the summer rainy season by increasing humidity to around 70% and providing a large water area with a depth of at least 10 cm.

• Light and temperature: Extend daylight to 12 to 14 hours, maintain daytime temperatures at 28 to 30°C, and reduce nighttime temperatures to 22 to 24°C.

• Pairing: Sexually mature males will call to attract females. Maintain clean water and a quiet environment to minimize stress.

After mating, females lay 200 to 2000 eggs per clutch. Eggs should be incubated in clean, still water at 24 to 26°C. They will sink within 24 hours. Tadpoles typically begin metamorphosis after about six weeks. During the tadpole stage, they can be fed algae wafers, boiled spinach paste, or fish food, gradually transitioning to insect-based diets. After metamorphosis, provide immediate access to land areas and moist habitats.

For general pet owners, unless intentional breeding is desired, prolonged cohabitation of males and females should be avoided to prevent accidental reproduction. If eggs or tadpoles appear, they should be properly managed and transferred to appropriate and legal care facilities. Release into the wild must never be attempted.

A tadpole of the Australian green tree frog（圖片來源：Jean-Marc Hero，採用 CC BY-SA 2.5 授權）

Preventing Invasive Spread

Although native to Australia and New Guinea, the Australian green tree frog is popular in the global pet trade due to its appealing appearance and docile temperament. It has been introduced into regions such as Florida and New Zealand, where it entered the wild. While the New Zealand population has been successfully eradicated, small populations still persist in Florida. Although no major ecological damage has been recorded so far, the potential impact remains a concern.

Any non-native species that establishes a population outside its native range may compete with local species, spread diseases, or alter ecosystems. Due to its adaptability, broad diet, and long lifespan, this species has the potential to become invasive in warm and humid environments if it escapes.

Key responsibilities for keepers:

1. Never release pet frogs into the wild, including artificial ponds or garden water features.

2. If unable to continue care, contact local reptile organizations, zoos, or wildlife rescue centers for proper rehoming.

3. Ensure enclosures are secure and escape-proof. Pay special attention to lids and openings, as this species is an excellent climber due to its adhesive toe pads.

Author: Shui-Ye You