National recovery plan for Stream Frogs of South-east Queensland 2001-2005
Prepared by Harry Hines
Queensland Parks and Wildlife Service
and the South-east Queensland Threatened Frogs Recovery Team, 2002
Appendix 1. Species Profiles
Cascade Tree frog Litoria pearsoniana (Copland 1961)
- Current distribution
- Conservation status
A small frog, males 24-29mm and females 31-37mm snout-vent length. Dorsal coloration highly variable, and can change seasonally. Ranges from green, through various combinations of green and brown to dark brown, with or without black spots or reticulations. A thin pale stripe runs from the nostril, through the eye, passes above the tympanum and continues along the flank to the mid-body. This stripe is bordered below by a brown band, broadening as it extends along the flank to the mid-body. There may be a pale stripe along the upper lip. The tympanum is distinct and usually brown in colour. The ventral surface is white or cream. The hidden parts of the groin and thighs are yellowish tan to brick red. The skin is smooth or shagreened above, granular below. The fingers and toes have well developed discs, but only the toes have extensive webbing. (Copland 1960, McDonald and Davies 1990, Meyer et al. 2001).
The mating call is a diphasic three note call lasting for 0.8 to 1.8 seconds; "Weeeak kuk kuk". Variations include: a very slow version of the first part of the call heard early in the evening, the first part of the call is made by one male and a second male completes the sequence, and individuals may merely repeat the last two notes several times. (McDonald and Davies 1990).
Reproductive activity occurs from August to April, peaking from October to early February. Females may possess the ability to breed more than once in a season. Amplexus is axillary, taking place near egg laying sites. Eggs are deposited in a clump of several hundred, attached to rocks, debris or aquatic plants in still, shallow pools adjacent to, or connected with the main stream. The eggs are dark, 1.1-1.3mm in diameter and are covered in a clear jelly capsule 3.0-3.5mm in diameter, generally obscured by grey or brown silt. Eggs hatch three to five days after spawning. Metamorphosis typically occurs two to two and a half months later, depending on temperatures (McDonald and Davies 1990).
Tadpoles are about 30mm long when metamorphosis commences. The dorsal surface is a light golden colour during early stages, darkening to brown; some specimens develop dark spots in the later stages. The ventral surface is unpigmented. The body is broader than deep with the greatest breadth behind the eyes. The mouth is ventral with two upper and three lower rows of labial teeth, with a median gap in the inner-most rows. Labial papillae surround the lateral and posterior margins of the mouth. The tail is moderately thick and has a rounded tip. The fins are transparent with dark spots. (McDonald and Davies 1990).
Inhabits streams in rainforest and adjacent wet sclerophyll forest at elevations of 200-1000m in south-east Queensland and north-east New South Wales. Activity is predominantly nocturnal, peaking on warm nights during and after rain, but the frogs may also be active on warm overcast days. Males call from low perches up to one metre above water, retreating to humid crevices during the day. During winter frogs may form large, mixed sex, aggregations in humid crevices with relatively stable temperatures. Within these crevices, hibernating animals, lethargic in behaviour with their eyes closed, form closely packed groups, with dorsal and ventral surfaces pressed against the crevice walls to reduce surface area (McDonald and Davies 1990).
Kandanga State Forest south-east Queensland (26° 26´S, 152° 24´E) south to Gibraltar Range north-east New South Wales (29° 31´S, 152° 25´E) (Hines et al. 1999) (Figure 6). Recent allozyme and DNA studies (Donnellan et al. 1999) indicate that the isolated population of L. pearsoniana at Kroombit Tops (24° 24´S, 151° 01´E - Figure 5) is genetically distinct and is an evolutionary significant unit (see Moritz 1994).
|Figure 6. Distribution of cascade tree frog Litoria pearsoniana.|
Czechura (1991) and McDonald and Davies (1990) recorded declines of L. pearsoniana in the late 1970s to early 1980s from the Conondale and Blackall Ranges in south-east Queensland. Corben (in McDonald 1991) suggested that this species had not suffered a conspicuous decline in the Conondale Range, but that it had disappeared from some streams in Brisbane Forest Park. Ingram and McDonald (1993) found L. pearsoniana breeding in small numbers in the Conondale, Border and Main ranges. During their survey, only two L. pearsoniana were heard during ideal weather conditions at East Kilcoy Creek (K. McDonald unpublished data) where it had previously occurred in hundreds during the study of McDonald and Davies (1990). Ingram and McDonald (1993) did not find it at Kondallila Falls in the Blackall Range, although it was common there in the 1970s (K. McDonald unpublished data). There are no reports of declines in New South Wales.
More recent studies have found the species to be reasonably widespread (summarised by Hines et al. 1999) with recovery at some sites. However, at other sites where seemingly suitable habitat exists, L. pearsoniana is currently at low densities. There are no recent records from sites at Girraween National Park where it was known historically, despite targeted surveys there.
The reasons for population declines are unknown. In the Blackall and Conondale Ranges the declines coincided with the period during which T. diurnus and R. silus disappeared. Large areas of this species' habitat have been degraded and continue to be degraded by introduced animals, e.g. feral pigs and domestic stock, invasion of weeds and timber harvesting (see Parris and Norton 1997 for discussion). Upstream clearing and urban development have reduced habitat and are likely to have affected downstream flow regimes and water quality in some localities (for example Kondallila Falls). Litoria pearsoniana is known to form large aggregations during winter (McDonald and Davies 1990); destruction of these sites may have severe local impacts on populations. Infections of a chytrid fungus (Berger et al. 1998) have been found on dead individuals from Main Range in south-east Queensland and from the population at Kroombit Tops. Other ill and dead L. pearsoniana have been found in the Conondale Range but these have not yet been examined to determine the cause (Hines et al. 1999).
Litoria pearsoniana is currently listed as Endangered in Queensland but is not considered threatened in New South Wales or nationally. It is listed as Insufficiently Known in the Action Plan, and meets IUCN (2001) criteria for Least Concern. Reassessment of its legislative status in Queensland, based on a more thorough analysis of recent survey and monitoring data, is warranted. Resolution of taxonomic problems within the species group is needed, particularly for the population at Kroombit Tops.