Diurnal basking in the Centralian Tree Frog Litoria gilleni and the Red Tree Frog Litoria rubella.
By Robert A. Valentic
Valentic, R.A, 1995 Monitor - Journal of the Victorian Herpetological Society inc. 7(1): 27.
Diurnal basking has been documented for the following hylids (tree frogs): Litoria aurea (Cogger, 1992; Hero et. al., 1991), L. meiriana (Cogger, 1992; Tyler, 1992), L. moorei (Cogger, 1992), L. raniiformis (Cogger, 1992; Hero et. al., 1991), L rothii (Tyler, 1992) and L. spenceri (Hero et. al., 1991). The purpose of this paper is to report on an observation of diurnal basking in L. gilleni and L. rubella. Both species were found sympatrically around the margin of a waterhole of the Kings Creek system, Watarrka (Kings Canyon) National Park, Northern Territory (24°16’S, 131°33’E).
Date: 20th March 1995.
Time: 12:10 - 13:05hrs (Central Standard Time). Weather Conditions: Air temperature in the low 30’s °C. Fine and clear with a slight breeze.
Habitat: Rugged sandstone range falling away to stepped cliffs with attenuated slopes. Boulder strewn, ephemeral watercourse within the intersecting gorge disconnected into isolated, stagnant pools. Riparian vegetation comprised of melaleuca, River Red-gum Eucalyptus camaldulensis, grevillea and cycads.
A total of eight L. gilleni were sighted perched on boulders on approaching the waterhole. The frogs ranged in length from 32mm-64mm snout-axilla (smallest and largest specimens measured respectively). Of these, five were perched in shaded locations on exposed rock faces. Three frogs were perched motionless atop boulders in direct sunlight. The three frogs did not alter their positions whilst being observed. L. rubella were also abundant in the area and behaved in a similar manner to the L. gilleni, with the majority of specimens perched in shaded locations. Several L. rubella basking in the sun were seen to swim and subsequently return to the same site.
Greg Fyfe, herpetologist and long term resident of Alice Springs has not previously observed diurnal behaviour in L. gilleni. Frogs found at Emily Gap and Simpsons Gap within the MacDonnell Range were active on rock faces after dark. All specimens located by day were sheltered within crevices. The waterholes of the upper Kings Creek would assumedly receive limited solar exposure due to the steep surrounding topography. Evening temperatures are also usually quite cool during March. L. gilleni and L. rubella may adopt certain behavioural ploys such as diurnal basking to bolster body temperature within the somewhat mild conditions created within the enclosed gorge.
Tyler (1989) has observed Cyclorana australis frequently basking diurnally during the wet season in high temperatures. Tyler wrote: “The frogs sit in an exposed position very close to the edge of pools. They give the impression of being asleep”. This behaviour is consistent with that observed in the basking L. gilleni. That L. gilleni can remain in sunlight for relatively long periods may indicate a high heat tolerance. In contrast, the smaller size of L. rubella may warrant the need for regular swimming forays.
Sincere thanks to Greg Fyfe for helpful advice.
Cogger, H.G. 1992. Reptiles and Amphibians of Australia. Fifth Edition. Reed, Sydney, N.S.W. 775pp.
Hero, J.M., Littlejohn, M. and Marantelli, G. 1991. Frogwatch Field Guide to Victorian Frogs. Department of Conservation and Environment. East Melbourne, Victoria. 108pp.
Tyler, M.J. 1989. Australian Frogs. Penguin Books Ltd. Ringwood. Victoria. 220pp.
Tyler, M.J. 1992. Encyclopedia of Australian Animals - Frogs. Angus and Robertson. Pymble, N.S.W. 109pp.
An adult female Centralian Tree Frog Litoria gilleni from Ormiston Gorge, West Macdonnell NP.
One of the sub-adult Centralian Tree Frogs Litoria gilleni found diurnally basking at Kings Canyon National Park, Northern Territory, Australia