The northern gastric brooding frog was discovered in Eungella National Park in northeastern Queensland, in pristine rainforest, where the only human disturbance was rudimentary walking trail through the forest. Here it occupied boulder-strewn streams, with individuals found between or beneath boulders in cascades and riffles, where the water is cool and clear. This species was not found in the still pools between fast-flowing water.
Because of the short space of time between the discovery of the species and its subsequent disappearance there was little opportunity to study the northern gastric brooding frog, however it appears that this species was very similar in its appearance and life-history traits to the southern gastric brooding frog. This frog was small and oval in shape, with females measuring 45-54 mm and males 33-41 mm. Individuals possessed large eyes that protruded upwards from their small, flattened head. The skin colour on their backs ranged from dull grey to slate, while the belly was bright yellow with dark brown markings. This frog possessed extensively webbed feet, an adaptation for life in fast-flowing water.
This frog, which fed on invertebrates and smaller frog species, employed one of the most original life-history strategies in the animal kingdom – gastric brooding. Females would swallow their own fertilised eggs and allow the young frogs to develop into tadpoles, and subsequently froglets, in her stomach. During the brooding period the female’s digestive process would shut down and her stomach would become so bloated that her lungs would collapse under the pressure, forcing her to rely solely on gas exchange through her skin for respiration. This behaviour was only documented once in this species, where 22 young were brooded in the stomach of one female, and the ‘birth’ of the brood lasted 34 hours! The only other species known to do the same is the southern gastric brooding frog, the only close relative of the northern gastric brooding frog, and a species which has suffered the same fate and is now also extinct.
The northern gastric brooding frog was first discovered in January 1984 around 11 years after the discovery of the southern gastric brooding frog. Initially it was thought to be relatively abundant across its range, however in January 1985 the first signs of decline were observed at lower altitudes within its range and by March of the same year it was only abundant at higher altitudes. By June of the same year it had completely disappeared across its range. It has not been recorded since 1985, despite efforts to locate individuals.
The exact cause of the species’ extinction is difficult to pin-point due to the rapid nature of the decline, and is still not known. It is now thought that the cause of the species disappearance is probably due to infection of a virulent pathogen, most probably the chytrid fungus Batrachochytrium dendrobatidis which has been implicated in the declines of many amphibian species worldwide.
It is now known that the southern gastric brooding frog, the closest relative of this species, was one of the first of a series of amphibian extinctions that occurred from the late 1970s until the early 1990s within Queensland and the Northern Territory. This series of extinctions began in southeast Queensland with the declines of the southern gastric brooding frog and the southern day frog, Taudactylus diurnus. It continued into the mid 1980s with the disappearance of the northern gastric brooding frog, and the severe decline in number of the northern day frog, Taudactylus eungellensis. Finally several species on the Big Tableland of northern Queensland became extinct in the early 1990s. This wave of population decline and species extinction occurred at a rate of about 100km per annum and is typical of disease epidemics spreading within a population without immunity.