Common name: waterfall frog
Scientific name: Litoria nannotis
Family: Hylidae (tree frogs)
Conservation status: This species is listed as Endangered in Queensland (Nature Conservation Act 1992) and nationally (Environment Protection and Biodiversity Conservation Act 1999). It is ranked as a low priority under the Department of Environment and Heritage Protection Back on Track species prioritisation framework.
The waterfall frog is a moderately large, robust species with males measuring 31-52 mm and females 48-59 mm. Males weigh up to 12 g and females up to 16 g. They are slate, olive or dull brown in colour, with irregular dark mottling. The belly is white or cream in colour, often with brown on the throat. The armpit and groin are flesh coloured. The skin is rough textured, finely granular, or with numerous small scattered warts above, and is granular below.
The fingers have basal webbing, and the toes are fully webbed. The finger and toe discs are well developed. Males have a large prepollex (additional thumb), with black spiny nuptial pads and accessory spines on the chest, head, forearm and thighs. The snout is bluntly rounded, the tympanum (ear) is indistinct and they have no vocal sac.
The tadpoles are adapted for fast flowing stream conditions with a suctorial mouth (to cling to their surroundings), muscular tail and narrow tail fins. The tadpole’s body colour is grey or olive-green with a dark abdomen, yellowish tail, and numerous diffuse dark-brown blotches across the tail muscle and fins.
Habitat and distribution
The waterfall frog inhabits fast-flowing streams around waterfalls and cascades in rainforest from 80-1300m altitude. They are generally found on boulders beside or behind waterfalls and cascades, but may be perched on trees or litter beside streams in moist conditions. Tadpoles are found predominantly in fast flowing sections of the stream, attached to rocks.
This species formerly occurred throughout the Wet Tropics between Paluma, north of Townsville and Mungumby Creek, 30 km south of Cooktown. Significant declines in upland populations have occurred since 1990. The waterfall frog is now absent from most upland sites, generally occurring below 400 m. Since 1997 adults have been found at three sites above escarpments, however these are small populations in which diseased and dying animals are commonly found through winter months.
Life history and behaviour
The call has been described as a repeated "crawk crawk crawk" or a gentle, popping, slow growl-like sound that is difficult to hear above the sound of flowing water.
The waterfall frog is primarily nocturnal, sheltering in refuges during the day from which they occasionally emerge to bask in the splash zone. Several individuals may aggregate in these diurnal refuges. At night they are much more active, being found in exposed positions within streams and streamside vegetation up to 35 m from the stream. Males may engage in foot-flagging displays.
Gravid (pregnant) females are encountered year round, as are males with nuptial pads. Large (2.7-3.4 mm diameter) unpigmented eggs are laid as a gelatinous clump under rocks in streams. The tadpoles graze on algal-covered rocks in fast flowing stream conditions.
Adults feed on a wide range of terrestrial and aquatic invertebrates including flies, dragonflies, beetles, bugs, cockroaches, ants and millipedes.
The waterfall frog is one of seven species of frogs occurring in the upland rainforest streams which have undergone substantial population declines in north-eastern Queensland. Since 1990, population declines or local extinctions have been noted at upland sites throughout the Wet Tropics Biogeographical Region. The waterfall frog is now absent from most upland sites.
The causes of the decline remain unknown. Richards et al (1993) found no obvious evidence that drought, floods, habitat destruction or pollution by pesticides, inorganic ions or heavy metals were responsible for the population declines. Current research is examining the possibility that a disease may have caused the decline of this species. Information on disease investigations and management can be located at the James Cook University website.
The recovery plan for the conservation of stream-dwelling frogs of the Wet Tropics bioregion makes the following management recommendations:
- Monitor historical localities to detect recovery
- Investigate disease in preserved animals and species occupying similar habitat
- Develop and refine husbandry techniques for rainforest stream dwelling frogs
- Continue studies on the autecology on this species
- Train park staff and community volunteers in identification of this species
- Implement monitoring by park staff of select locations within the national park estate where the waterfall frog formerly occurred
Curtis LK, Dennis AJ, McDonald KR, Kyne PM, and Debus SJS. 2012 Queensland’s Threatened Animals, CSIRO, Victoria, Australia
Northern Queensland Threatened Frogs Recovery Team. 2001. Recovery plan for the stream-dwelling rainforest frogs of the Wet Tropics biogeographic region of north-east Queensland 2000-2004. Report to Environment Australia, Canberra. Queensland Parks and Wildlife Service, Brisbane.