Southern dayfrog Taudactylus diurnus. Photo: EHP
Common name: southern dayfrog
Scientific name: Taudactylus diurnus
Conservation status: This species is listed as Endangered in Queensland (Nature Conservation Act 1992) and Extinct nationally (Environment Protection and Biodiversity Conservation Act 1999). It is considered a low priority under the Department of Environment and Heritage Protection Back on Track species prioritisation framework.
A small frog, snout-vent length of males measuring 22.0-27.2 mm and females 23.3-30.6 mm. The dorsal surface is grey or brown with darker mottling. A pale bar occurs between the eyes, bordered behind by a dark brown patch. A short dark stripe runs from the eye to the base of the forearm, sometimes with a pale band bordering the lower edge. A dark, irregular, slightly raised H-shaped mark is present over the shoulders, and an irregular pale patch may be present over the pelvic region.
Limbs have irregular dark crossbands. Ventral surface is cream, yellowish-white or blue-grey, with or without grey spots. The throat is more heavily spotted or mottled with grey, sometimes appearing grey with yellow spots. The skin is smooth, finely granular, or with a few low warts above, smooth below. Digits have wedge-shaped discs and are unwebbed, though toes have broad fringes.
Habitat and distribution
The southern dayfrog inhabits montane rainforest, tall open forest and other riparian vegetation with a closed understory along permanent and temporary streams at elevations between 350 and 800 m. It prefers permanent streams with a rocky substrate, but will use streams with a wide variety of substrates provided the water is not very muddy. Active frogs may be found among low vegetation, rocks, leaf litter and other debris, generally within 10 m of water, although they have been recorded about 22 m from water in wet weather. Individuals frequently enter the water, swimming from point to point or sitting half-submerged. At night they shelter under rocks and debris or within crevices.
The southern dayfrog is the southern-most representative of the genus, occurring in three sub-coastal ranges (Blackall, Conondale & D'Aguilar Ranges) near Brisbane, south-eastern Queensland (Hines et. al. 1999). The southern dayfrog has not been seen sighted in the wild since 1979 and is most likely extinct. Continued efforts to relocate the species have failed.
Life history and behaviour
The southern dayfrog is a diurnal species, with its activity beginning at sunrise and ceasing soon after sunset. This species is generally very active, but will sit motionless for periods while basking in sunlit patches or on warm rocks. Individuals escape danger by leaping into the water and swimming away, or hiding on the bottom among rocks or loose mud. The southern dayfrog's activity appears to be restricted by temperature, and this species is intolerant of desiccation.
Although lacking vocal sacs, a call is emitted and resembles a soft chuckling, repeated 1-2 or 4-5 times in quick succession every 4-5 mins, reminiscent of T. eungellensis and the chuckle call of T. acutirostris. Active southern dayfrogs have been observed year round, although less frequently during cooler winter months. Breeding occurs in warm weather after or during heavy rain between October and May, peaking in the January to March period. Eggs are deposited in gelatinous clumps under rocks in the water.
Tadpoles are moderately sized, with an umbrella-shaped lip. The tadpoles may be found year round and are bottom dwellers, feeding by scraping food from the substrate.
The southern dayfrog is one of five species of upland rainforest stream-dwelling frog which has declined in South East Queensland during the last 20 years (Ingram & McDonald 1993). It underwent a sudden and unanticipated decline during the late 1970's, the last specimen was reported in 1979 (Czechura & Ingram 1990). Regular searches since that date have failed to rediscover the species.
The causes of the population decline remain unknown. Studies have not found any obvious evidence that over-collecting, pollution from logging or gold panning, or drought were responsible for the population decline of the closely associated R. silus. Ingram (1990) argued that the disappearances might be due to late rains falling in the cooler months.
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 National recovery plan for stream frogs of South East Queensland 2001-2005 makes the following management recommendations for the conservation of stream frogs of South East Queensland:
1. Ongoing survey of historical sites and sites with suitable habitat.
2. Provision of public information and education to raise awareness regarding this species.
Cogger HG. 2000. Reptiles and Amphibians of Australia. Reed New Holland: Sydney.
Covacevich JA and McDonald KR. 1993. Distribution & conservation of frogs and reptiles of Qld rainforests. Memoirs of the Qld Museum. 34(1):189-199.
Czechura GV and Ingram GJ. 1990. Taudactylus diurnus & the case of the disappearing frogs. Memoirs of the Qld Museum. 29(2):361-365.
Department of Sustainability, Environment, Water, Population and Communities. 2012. Taudactylus diurnus Southern dayfrog in Species Profile and Threats Database.
Hines H, Mahony M and McDonald KR. 1999. An Assessment of Frog Declines in Wet Subtropical Australia. In Campbell, A (ed), 'Declines and Disappearances of Australian frogs'. Environment Australia, Department of the Environment and Heritage: Canberra. 234 pp.
Ingram GJ. and McDonald KR. 1993. An update on the decline of Qld's frogs. Pp 297-303 In Lunney D. and Ayers D. (eds) Herpetology in Australia. A Diverse Discipline. Royal Zoological Society of NSW, Mosman.