This species is endemic to the Wet Tropics Bioregion in north Queensland, from Paluma to Cooktown (Hero and Fickling 1994; Williams and Hero 1998, 2001) at altitudes between 180 and 1,300m asl (McDonald 1992). It includes three deeply divergent mitochondrial DNA lineages, distributed from Paluma to Tully River, Tully River to Lamb Range, and Mount Lewis to Big Tableland (Schneider, Cunningham and Moritz 1998).
Habitat and Ecology
Litoria nannotis is a habitat specialist, restricted to rocky stream habitats in rainforest or wet sclerophyll forest where there is fast-flowing water, waterfalls and cascades (Liem 1974b; McDonald 1992). It is a stream dwelling and breeding species (Hodgkison and Hero 2001), but, unlike most stream-breeding frog species that live in the adjacent forest and use the stream habitat for breeding, the stream is the primary habitat for both male and females throughout the year (Hodgkison and Hero 2001, 2002). On several occasions the adults and juveniles were noted to form small aggregations (4-6 individuals) amongst large boulders behind waterfalls (Liem 1974b; J-M. Hero pers. obs.). Gravid females and males with nuptial pads are encountered all year round (Martin and McDonald 1995). Unpigmented eggs numbering 136-216 (1.98-3.4mm in diameter) are laid in gelatinous egg masses under rocks in water (Liem 1974b; Hero and Fickling 1996). Liem (1974b) described the larva and noted that it is one of the few species of frog known to exhibit larval adaptations to torrent environments of Australia, such as a streamlined body shape, large suctorial mouthparts and a muscular tail. Richards (1992) also provided information on the larvae of the L. nannotis group.
This species was first noted to have declined in 1990 (Richards, McDonald and Alford 1993), since it had apparently disappeared from most upland sites south of the Daintree River. The species occurred at all lowland sites, and at upland sites north of the Daintree River during summer surveys in 1991–1992. In 1994 it was sighted at several locations above 600 m asl on Mount Father Clancy. Lowland populations surveyed in Tully Gorge appeared to be relatively stable between 1995 and 1998 (J.-M. Hero pers. comm.). At the southern end of its range it was last observed in Mount Spec State Forest in 1991 (Richards, McDonald and Alford 1993); however, adults occurred at a lower elevation site in a different creek system (Crystal Creek Stone Bridge, 300m asl) from January 1994 to September 1995 (J.-M. Hero pers. comm.). This species is currently known to have stable populations at lowland sites (Hero et al. 1998, McDonald and Alford 1999).
The reason(s) for the decline are unknown. 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, and habitat destruction is no longer a major threat (McDonald and Alford 1999). Research is examining the possibility that disease, such as a viral infection or chytrid fungus, may have contributed to the decline of this species (Berger, Speare and Hyattt 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 L. nannotis (Richards, McDonald and Alford 1993). However, there has been very little research into the impact of feral pigs on native frog populations (Richards, McDonald and Alford 1993).
There is a need for continued and strengthened protection of habitat in the Wet Tropics, including an improved management plan that involves dealing with the threat posed by feral pigs. Further research into the reasons for the decline of this species in pristine habitat is necessary.
Jean-Marc Hero, Richard Retallick 2004. Litoria nannotis. In: IUCN 2014