This species, an Australian endemic, formerly occurred across two thirds of the Wet Tropics from Douglas Creek near Cardwell to Alexandra Creek, Thornton Peak north-east Queensland (Hero and Fickling 1994) at altitudes between 380 and 1,020m asl (McDonald 1992).
Habitat and Ecology
This species is a rainforest specialist, endemic to the Wet Tropics Bioregion (Williams and Hero 1998, 2001) found in upland rainforest and wet sclerophyll forest along fast-flowing streams where there is white water from riffles and cascades (Liem 1974b; McDonald 1992). It is usually found perched on rocks or overhanging vegetation adjacent to the water (Liem 1974b). Little is known about the life history of this species. Mating calls have been heard from October to March (Liem 1974b). From 86-90 large unpigmented eggs (1.9-2.5mm diameter) are laid under rocks in riffles (Richards 1993a; Hero and Fickling 1996). Richards (1992) described the tadpole and noted that it is one of the few species of tadpole known to exhibit adaptations to torrent environments of Australia, including a streamlined body shape, large suctorial mouthparts and muscular tail. Tadpoles commonly overwinter in upland streams, although those hatching in early summer can metamorphose before the next autumn (Richards 1992).
It was once moderately common in suitable habitat, but it has undergone a catastrophic decline. Adults were last recorded in April 1990, and tadpoles and metamorphs were last recorded in November 1990 on the Carbine Tableland (Richards, McDonald and Alford 1993). However, this species had apparently disappeared from sites on the Atherton Tableland much earlier (Richards, McDonald and Alford 1993). It was recorded from various sites on the Atherton Tableland prior to 1973 (Liem 1974b), but was not encountered in Danbulla State Forest during 1989-1992 or at any Atherton Tableland site during surveys conducted between 1991 and 1992 (Richards, McDonald and Alford 1993). No information is available on population structure or genetic variation (M. Cunningham pers. comm.). The species might now be extinct.
The reason(s) for the decline of this species are unknown, although chytridiomycosis must be strongly suspected. Richards, McDonald and Alford (1993) reject drought, floods, habitat destruction, or pollution by pesticides, inorganic ions or heavy metals. The habitat of the species in the Wet Tropics has been protected since 1988; therefore, habitat destruction is no longer a threat (McDonald and Alford 1999). Current research is examining the possibility that disease, such as a viral infection or chytrid fungus, might have contributed to the decline of this species (Berger, Speare and Hyatt 1999). Feral pigs are a potential cause of riparian habitat damage and adult frog mortality (Richards, McDonald and Alford 1993). The activity of feral pigs has been recorded to have increased over the period 1989-1992 in an area previously inhabited by this species (Richards, McDonald and Alford 1993).
The habitat of the species in the Wet Tropics has been protected since 1988. This species is a priority for immediate survey work to determine whether or not it still survives at the localities from which it has previously been recorded. Research is also needed into the possible reasons for the decline of the species. Given the possible threat of chytridiomycosis or some other disease, surviving individuals might need to form the basis for the establishment of an ex-situ population.
Jean-Marc Hero, Michael Cunningham, Ross Alford, Keith McDonald, Richard Retallick 2004. Litoria nyakalensis. In: IUCN 2014