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Predation on Tornier's Frog Litoria tornieri (Anura: Hylidae) by a Dolomedes like spider (Araneomorphae: Pisauridae).

Text: Rob Valentic

Photos: Rob Valentic & Grant Turner

INTRODUCTION

While anecdotal accounts exist, well documented cases of invertebrates preying on reptiles and frogs in Australia are few.  The common and scientific names of spiders mentioned below follow Main (1984).  The Sydney Funnel-web Spider Atrax robustus and Brush-footed Trapdoor Spiders (Barychelidae) have been documented preying upon frogs (Brunet, 1994).  A photo depicting a Barking Spider Selenocosmia sp. preying on Litoria lesueri appeared in ’Australia’s Dangerous Creatures’ (Underhill, 1993).  Mascord (1993) wrote of an adult female Selenocosmia crassipes that killed and ate a young Litoria caerulea in 6 hours.  Main (1984) also lists examples of spiders eating frogs.  Orange (1990) recorded a Redback Spider Latrodectus mactans preying upon Parasuta monachus, a small elapid species.  Two other references relating to spider predation on snakes are also cited in the paper.  Danny Goodwin (pers. comm. 1996) has noted several cases of Latrodectus sp. preying on Weasel Skinks Saproscicus mustelinus.  A large species of preying mantid Hierodula werneri has also been observed catching frogs at Darwin (Ridpath, 1977).  Nash (1963) refers to a large brown mantid consuming a juvenile Litoria raniformis (referred to as a Golden Bell Frog).  Nursery-web Spiders Dolomedes spp. ‘capture tiny fish, tadpoles, insects and skinks’ (Brunet, 1994; McKeown, 1943).

The following note records a large female Dolomedes like spider (the spider was not reliably identified as a Dolomedes sp., as opposed to Megadolomedes for example, and is thus referred to as ‘a Dolomedes like spider’ in this note) subduing and feeding on an adult Litoria tornieri at Edith Falls in the north-west section of Nitmiluk (Katherine Gorge), National Park, Northern Territory (1411’S, 13211’E).

OBSERVATION

Date:    10 November 1991

Time:    20:15 hours (Central Standard Time)

Weather conditions:    Full moon, clear night, (air temp. of 26C with high relative humidity)

Habitat: The embankment of a large plunge-pool of the Edith River system.  Riparian flora consisting predominantly of Pandanus aquaticus and Melaleuca sp.  Understorey essentially bare and covered by a thick layer of leaf litter.

Notes:  Whilst searching for frogs by torch-light a loud disturbance amongst leaf litter some two metres from the river edge was noted.  Upon investigation a frog was observed leaping awkwardly as though impeded.  On closer inspection a large Dolomedes like spider was discovered straddled atop the frog’s dorsum, its long limbs wrapped tightly around and completely enveloping the prey.  The spider’s chelicerae were pressed firmly into the frog’s neck region.  The frog, which constantly jumped in a limited area (1m<), was identified as L. tornieri.  The spider appeared undeterred by these attempts to remove it and maintained a strong grasp.  After ten minutes (20:25 hours), the L. tornieri appeared dead and the spider began feeding by raising and subsequently lowering the fangs into the frog’s anterior half.  Throughout the observation the long legs remained tightly wrapped around the frog.  At 22:25 hours the site was again inspected although no sign of prey or predator could be located.PA0006218684

DISCUSSION

The frog did not emit a distress call during the above encounter.  Nash (1963) refers to the distress call of a young Litoria raniformis which was being consumed by a mantid.  Perhaps L. tornieri are incapable of a distress call or vocalisation is restricted to males of this species.  The gender of the above L. tornieri was not determined during the interaction.  Brunet (1994) states that Dolomedes typically capture prey within water where the prey is subdued and dragged to the water’s edge and devoured.  L. tornieri are abundant in the leaf litter beneath Pandanus at the site (pers. obs.).  It is possible that the spider may have ambushed the frog on land given the distance from the water that the above encounter occurred.  The spider may have dragged the frog away from the site to continue feeding referring to the 6 hour consumption span noted by Mascord (1993).  Mascord wrote: “All that remained of the frog in that time was a ball of debris 2 cm in diameter which contained bones and skin in a mushy state”.  A number of small frog species that are common at this site such as Litoria bicolor, L. meiriana, L. rubella and Opisthodon ornatus (pers. obs.) may also be considered potential prey for Dolomedes like spiders.

Wolf Spider Lycosa godeffroyi     
A large female Garden Wolf Spider Lycosa godeffroyi preying upon an adult Garden Skink Lampropholis delicata.  Omeo, north-eastern Victoria, Australia

Predation of Dainty Green Tree Frog Litoria gracilenta by a Brown Huntsman Spider Heteropoda sp.  Predation of Dainty Green Tree Frog Litoria gracilenta by a Brown Huntsman Spider Heteropoda sp.
Predation of a Dainty Green Tree Frog Litoria gracilenta by a Brown Huntsman Spider Heteropoda sp. near Tully, north-eastern Queensland.  Photographs by Grant Turner.

ACKNOWLEDGEMENTS

Thanks to Grant Turner for his improvements to the first draft of the manuscript and for his help in locating references.  I would also like to thank referees Lothar Voigt and David Millar for their helpful comments and improvements to the manuscript.

REFERENCES

Brunet, B.S. (1994).  The Silken Web - A Natural History of Australian Spiders.  Reed Books, Chatswood, NSW. 208pp.
Main, B.Y. (1984). Spiders. Collins Books, Sydney, NSW. 296pp.
Mascord, R. (1993). Australian Spiders in Colour. Reed Books, Chatswood, NSW. 112pp.
McKeown, K.C. (1943). Vertebrates captured by Australian Spiders. Proceedings of the Royal Zoological Society of NSW. 1942-1943: 17-30.
Nash, K.M. (1963). Along the By-ways (Letters to the Editor). The Victorian Naturalist. 79(1):11
Orange, P. (1990). Predation on Rhinoplocephalus monachus (Serpentes: Elapidae) by the Redback spider Latrodectus mactans. Herpetofauna. 20(1):33.
Underhill, D. (1993). Australia’s Dangerous Creatures. Reader’s Digest, Surry Hills, NSW. 368pp.
Ridpath, M.G. (1977).  Predation on frogs and small birds by Hierodula Werneri (Giglio - Toss) (Mantidae) in tropical Australia. Journal of the Australian Entomological Society. 16:153-154.