Frog (Green & Golden Bell Frog) Litoria aurea
Species: L. aurea
Binomial name: Litoria aurea
Common name: Green and Golden Bell Frog, Green Bell Frog, Green and Golden Swamp Frog and Green Frog
The Green and Golden Bell Frog (Litoria aurea) is a ground-dwelling tree frog native to eastern Australia. In the late 1860s several consignments of these frogs were received from Sydney and released by the Auckland Acclimatisation Society. There have been several attempts to establish populations of this species in the South Island, but it appears that the climatic conditions are not favourable and the species is restricted to the upper half of the North Island.
Despite its classification and climbing abilities, it does not live in trees and spends almost all of its time close to ground level. It can reach up to 11 centimetres in length.
Coloured gold and green, the frogs are voracious eaters of insects but will also eat larger prey such as worms and mice. Unlike most frogs, they are active at day although this is mostly to tan in the sun. They tend to be less active in winter except in warmer or wetter periods, and breed in the warmer months. Males reach maturity after around nine months, while for the larger females, this does not occur until they are two years old. The frogs can engage in cannibalism, and males frequently attack and injure one another if they infringe on one another's space.
Many populations inhabit areas of frequent disturbance, such as golf courses, disused industrial land, brick pits and landfill areas. In Australia it has endured major population declines. Despite the situation in Australia, the frog remains abundant in New Zealand and several other Pacific Islands, where it has been introduced.
The Green and Golden Bell Frog is a large, stout frog; adults range from 4.5 to 11 centimetres in length; typical specimens measure 6 to 8 centimetres. Mature male Green and Golden Bell Frogs are generally smaller than mature females, and the colour on their dorsal surface differs greatly to females. It may be almost completely green, of shades from dark pea-green to bright emerald; green with metallic, brassy, dull copper-brown, or gold markings; or almost completely bronze. Generally, females tend to have more green patches than males. During the cooler months (May–August), when Green and Golden Bell frogs are inactive, colouration may darken almost to black. They can also darken in this way by simply staying in a dark place for a few minutes and the colour can also evolve during the frog's lifetime. A creamy-white or pale yellow stripe, bordered above with gold and below with black, extends from behind the eye, across the typically copper-coloured tympanum to the groin. This stripe rises to form a dorso-lateral fold towards the groin. Another stripe of the same colour begins below the eye and continues to the shoulder. The abdomen is cream or white, and has a coarsely granular texture. The legs are green, bronze, or a combination of both, and the inside thigh and groin are blue-green.
Mature males develop a yellowish colouration to the vocal sac on the throat. The tympanum is distinct and ovular in shape, and the species has enlarged toe discs to aid in climbing. As this species is often found in water, the fingers are free from webbing while the toes are almost completely webbed. When in breeding condition, males develop nuptial pads on their thumbs, which are used to grip females during mating. These are coloured brown during the breeding season, but are inconspicuous and paler during the rest of the year. During the breeding season, females develop a blueish hue on their feet, while males' legs turn rusty orange.
Green and Golden Bell Frog demonstrating camouflage within reedy environments. As a member of the tree frog family, the Green and Golden Bell Frog spends much time basking in the sun on vegetation, rocks and reeds, usually near water, or hopping around between such places. Unlike most frog species it is often active during the day. When handled, this species secretes a slimy acrid mucus which consists of 17 aurein peptides. Thirteen of these show broad-spectrum antibiotic and anti-cancer activity, which is useful in fighting off harmful microorganisms. The secretion makes the frog slippery and hard to grip, and is poisonous to some other species of frogs, so it is a useful defensive tool for Green and Golden Bell Frogs. Male Green and Golden Bell Frogs often fight one another if they come within 1 m of each other, frequently leading to injuries.
Though found in all types of habitats it is most typically found in short-lived freshwater ponds that are still, shallow, unshaded and unpolluted; and it tends to avoid waters that contain predatory fish, whether native or introduced. However, it is most often found in areas that have been affected by human habitation. The frog prefers water bodies that support emergent vegetation such as reeds, bulrushes and flaxes for basking, and winter habitats consist of available shelters around the breeding site, which can be vegetation, rocks, rubbish or human debris and discarded building materials. Grassy habitats are usually close at hand to provide suitable terrestrial feeding grounds. Although its legs provide much grip, the frog does not choose to climb trees or live up them to any significant extent. They spend most of their time within 10 cm of the ground and rarely venture more than a metre above the ground.
The Green and Golden Bell Frog can travel far in a single day or night; distances of 1–1.5 km have been recorded. Tagging experiments have shown that some can move up to 3 km and in total and that some travel several kilometres from the closest breeding habitat. However, there is evidence that the species tends to return to or remain at an identified site, provided that the habitat stays appropriate for its needs, else it will move away. In general, the frogs stay within areas of 100–700 m2. The frog is well-equipped for survival on land. They can rehydrate by absorbing moisture through their ventral skin, and evaporative water loss occurs at a very low rate indicative of a watertight skin. Some have been observed up to 400 m from the nearest body of water.
During the winter months, the frog tends to be inactive, staying in one place, whereas it moves around during the warmer months to search for food and mating partners.
Although the frog is active during the day, this is restricted to leaving its shelter to sunbathe. It tends to not actively feed or forage during the day, hunting insects only if they move into their vicinity.
The voracious adults have a very broad diet, including insects such as crickets, larvae, mosquito wrigglers, dragonflies, earthworms, cockroaches, flies and grasshoppers. It is also known to eat freshwater crayfish and slugs. It eats other frogs, even of the same species. It has a strong tendency for cannibalism.
The tadpoles feed on detritus, algae and bacteria. Tadpoles in a more advanced phase of development may show a preference for vegetable matter but also scavenge or become carnivorous on aquatic life.
The Green and Golden Bell Frog breed in the warmer months from October to March, although some cases have been recorded earlier at the end of winter. During the breeding season, males call, usually while floating in the water, but sometimes on vegetation at the side of a pond, mainly at night. They do so with a deep growl that has been described as a four-part "walk-walk sound"—likened to the sound of a motorbike changing gears. Males appear to reach maturity at around 45–50 mm, at between 9 and 12 months, and at this size begin to develop a grey to brownish yellow wash beneath the chin. This indicates the development of a vocal sac and thus an ability to commence calling behaviour. Observations show that females reach sexual maturity at two years as those smaller than 65 mm are not seen in amplexus; this length is not reached until the second season after metamorphosis. Females spawn can shed up to 26% of their weight when spawning, while males have also been seen to lose weight during breeding, because they are doing less eating.
During amplexus, the males grab the females near their armpits after climbing on their backs. The frogs may move up to 100 m during amplexus before the female lays her eggs. During the laying of the eggs, the pair of frogs remain in amplexus and the male is assumed to fertilise the eggs with his sperm. Males are also seen to paddle their rear legs during this time, which is speculated to accelerate fertilisation. The egg-laying and fertilisation process takes around five minutes. An average of 5,000 eggs is deposited amongst aquatic vegetation in a gelatinous mass; however, a clump of 11,682 has been recorded. The female moves around while depositing, leaving a trail of eggs that sometimes entangles upon itself. Initially, the mass floats, but sinks up to 12 hours after laying, or when disturbed. The eggs are distinct from those of other frog species; they are 2–2.5 mm wide upon deposition and are bicoloured, black at one end and white at the other. They immediately begin to expand, quickly reaching around 4 mm across, before sinking. When first laid they float with the black pointing up, but after sinking, the orientation becomes disordered. Two to five days later, the tadpoles hatch out, although there have been reports of the process taking only a few hours on occasions. Given the large number of eggs that hatch per female, it is believed that given the scarcity of mature frogs, tadpole survival rates are very low. Upon hatching, the tadpoles are around 2.5–3 mm in snout-vent length and about 5–6 mm including the tail. The tadpoles of the Green and Golden Bell Frog are large, reaching 80 millimetres in length, but size varies greatly and most are much shorter. The body is usually as wide across as it is deep. The fin has a yellow tinge and is considerably arched. The musculature is moderate and tapers to a fine point as does the fin. The body wall is translucent yellow with darker areas over the abdomen. Just before its limbs form, the tadpole begins to develop the greenish colouration of the adult. Tadpoles usually swim within 30 cm of the water surface, or remain stationary at the bottom. They often move together in groups akin to schools of fish. Towards the end of the tadpole phase, hind legs appear, followed by front limbs, and the phase ends when the front limbs are developed. This normally occurs between October and April due to the breeding season, but tadpoles been observed in the wild throughout the year, suggesting that some tadpoles over winter. The length of the tadpole stage, in the wild and in captivity, is usually between 10 and 12 weeks but can range from 5 weeks to a year. At the beginning of the metamorphling stage, all limbs are present and developed, along with a tail. During this phase, the tail is resorbed, and the only other visible change is the spiracle closing. The process is slowed at low temperature, but generally takes between three to eight days after the tadpole stage is complete. While it is known to live 10-15 years in captivity, the frog's lifespan in the wild is not well understood.
The call of the Green and Gold Bell frog: http://www.doc.govt.nz/pagefiles/3018/aurea.wav
Recorded at Pukekura Park
A Litoria aurea with a darker colouration (see above text)
Thanks to Wikipedia for text and information http://creativecommons.org/licenses/by-sa/3.0/