This species is endemic to the Wet Tropics Bioregion (Williams and Hero 1998, 2001) and occurs from Broadwater Creek National Park to Amos Bay, north Queensland, at altitudes between sea level and 1,180m asl (McDonald 1992). Three genetic lineages of Litoria rheocola have been identified, based on mitochondrial DNA, distributed from Kirrama Range to Palmerston National Park; Bartle Frere to Harris Peak; and from Mt Lewis to Big Tableland (Schneider, Cunningham and Moritz 1998). Each of these lineages carries substantial genetic variability (Schneider, Cunningham and Moritz 1998).
Habitat and Ecology
This is a rainforest specialist, restricted to fast-flowing rocky creeks and streams in rainforest as well as wet sclerophyll forest (Liem 1974b; McDonald 1992). Within these streams they are often found in the slower more open sections, away from waterfalls (Hodgkison and Hero 2002). Individuals can be found on rocks, logs and vegetation in or adjacent to streams (Hero and Fickling 1994). There are differences in habitat use between males and females of the species. Females and juveniles use streamside vegetation more frequently than males. In contrast, males display strong fidelity to the rocky stream environment. Calling males and gravid females have been observed throughout the year (Liem 1974b). Breeding has been observed in most months, except during cold winter nights, and seems to reach a peak between November and March (Liem 1974b; Dennis and Trenerry 1984). Males call from rocks or boulders in creeks or from vegetation overhanging water along streams and creeks (Liem 1974b). The males also appear to display inter-male spacing, with males rarely found within 1m of each other, which is possibly a territorial response to low availability of females (Hodgkison and Hero 2002). A number (46-63) of unpigmented eggs (2.4-2.6mm in diameter) are laid in compact gelatinous clumps under rocks in water (Liem 1974b; Hero and Fickling 1996). Larvae can be found in fast-flowing sections of streams and adjacent pools in highly oxygenated water, clinging to rocks and other substrates (Liem 1974b; Hero and Fickling 1994). Liem (1974b) described the larvae of this species as torrent dwelling, having flattened bodies, large suctorial mouthparts and muscular tails. Richards (1992) and Hero and Fickling (1994) also provided detailed information on the larvae of this species.
This species was first noted to have declined in 1989 (Richards, McDonald and Alford 1993). In 1990 several sites were sampled between the Kirrama Range and Cooktown. L. rheocola was common at all foothill and lowland sites and was recorded at some upland sites in the Kirrama Range in April and on the Carbine Tableland in January of that year (Richards, McDonald and Alford 1993). It was abundant in Danbulla State Forest (at 700m asl) in September 1982, but was not recorded there during monitoring between 1989 and 1992 (Richards, McDonald and Alford 1993). It has since disappeared from most upland sites south of the Daintree River (Richards, McDonald and Alford 1993). Richards, McDonald and Alford (1993) reported only two adults at Bobbin Falls on the Atherton Tableland, although the species has been found regularly in that area between 1998 and February 2000 (R. Retallick pers. comm.) and 2001-2002 (K.R. McDonald pers. comm.). At O’Keefe Creek, Big Tableland, this species has occasionally reappeared near a 400m asl site, but has not established resident populations and is absent at another monitoring site at 600m asl (McDonald and Alford 1999). Adults and larvae remained common at upland sites north of the Daintree River (Richards, McDonald and Alford 1993) but disappeared in 1993 (M. Cunningham pers. comm.). Interestingly, the lowland populations still exist (McDonald and Alford 1999).
The reason(s) for the decline of this species 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; 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, may have contributed to the decline of this species (Berger, Speare and Hyatt 1999). In recent experiments involving the translocation of larvae and adult frogs to sites previously occupied by the species, a clear pattern was evident in the disease results, and nearly all of the animals found dead showed signs of chytridiomycosis (Retallick 1999, 2000, 2001). It is unknown as to whether this disease was solely responsible for the disappearance of L. rheocola at these sites. 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. rheocola (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).
Listed as endangered in Queensland, and therefore protected by state legislation. The habitat of the species in the Wet Tropics has been protected since 1988. A recovery plan is in place.
Jean-Marc Hero, Ross Alford, Michael Cunningham, Keith McDonald, Richard Retallick 2004. Litoria rheocola. In: IUCN 2014