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Two lizards and a frog occupying multiple shelter sites within a hollow tree.

By Rob Valentic.

INTRODUCTION

A variety of reptile and frog species have been documented sharing the same cover (Rankin, 1975; Maryan and Robinson, 1987; Orange, 1992; Valentic 1993).  This report details the discovery of a Spotted Tree Monitor Varanus scalaris, Giant Tree Gecko Pseudothecadactylus australis and a Green Tree Frog Litoria caerulea utilising separate hollows within a single standing Broad-leaved Paperbark tree Melaleuca viridiflora.

Giant Tree Gecko Pseudothecadactylus australis from Cape York Peninsula, Queensland, Australia.
The Giant Tree Gecko Pseudothecadactylus australis from Cape Weymouth, Cape York Peninsula, north-eastern Queensland, Australia.

OBSERVATION 

Location:  Cape Weymouth, Cape York Peninsula, north Queensland (127’S, 14326’E).

Habitat:  Gently sloping paperbark woodland with a dense understorey of giant speargrass Heteropogon triticeus interspersed with scattered, low granite outcroppings.

Date:  17th  May 1993.  

Time:  11:40-12:20hrs (Eastern Standard Time).

Weather Conditions:  28C, heavy (100%) cloud cover with a gentle onshore breeze.

Notes:  These observations were made whilst participating in the Cape York Peninsula Land Use Study under Iron Range Zoologist in charge, Luke Leung.  We located a Pseudothecadactylus australis in a standing dead tree (Melaleuca viridiflora, diameter at breast height 45 cm, total height 5 metres approx.) by tapping on numerous tree trunks as described by Cameron and Cogger (1992).  We decided to dismantle the tree in order to measure and photograph the gecko.  The lizard (a male, SVL: 107mm) could be heard vocalising within a hollow branch 2.1metres above ground level.  The sectioning of this branch facilitated viewing inside the main trunk where an adult Varanus scalaris  (SVL: 246mm) was discovered about 2 metres above ground level.  The cavity within the main trunk steadily narrowed and a sub adult Litoria caerulea (S-A: 56mm) was also discovered utilising a tight recess 320mm above the varanid’s position.  

DISCUSSION 

V. scalaris forage widely in search of arthropods and small vertebrates (Wilson and Knowles, 1988).  It is possible that the varanid was disturbed whilst in the process of investigating the hollow for potential prey.  In this case it is doubtful that the varanid would be successful due to the restricted diameter of the hollows occupied by P. australis and L. caerulea.  The narrow spaces would effectively exclude the bulk of the varanid.  If all three species were in fact sharing the tree, this may indicate a scarcity of arboreal refugia in the immediate area.  Litoria caerulea and P. australis, being nocturnal, may not usually be vulnerable to predation by a diurnal varanid while active, and could possibly cohabit the tree with little risk of predation.

REFERENCES

Cameron, E.E. and Cogger, H.G. 1992. The Herpetofauna of the Weipa Region, Cape York Peninsula.  Technical Reports of the Australian Museum.  Number 7, 200 pp.

Maryan, B. and Robinson, D. 1987.  Field compatibility observation.  Herpetofauna 17(1):11.

Orange, P. 1992.  Miscellaneous herpetological observations.  Herpetofauna 22(2):44.

Rankin, P.R. 1975.  Exploitation of a woodpile in Northern Queensland by a community of reptiles and amphibians.  Herpetofauna 8(2):4-6.

Valentic, R. 1992.  The Big Desert Wilderness - a field excursion.  Monitor - Bulletin of the Victorian Herpetological Society 5(2):59-64.

Wilson, S.K. and Knowles, D.G. 1992.  Australia’s Reptiles - A photographic reference to the terrestrial reptiles of Australia.  2nd edition.  Cornstalk Publishing, Pymble, NSW, 447 pp.