The lesser hairy-footed dunnart (Sminthopsis youngsoni, Dasyuridae) is a generalist marsupial insectivore in arid Australia, but consumes wolf spiders (Lycosa spp., Lycosidae) disproportionately often relative to their availability. This project tested the hypothesis that this disproportionate predation is a product of frequent encounter rates between the interactants due to high overlap in their diets and use of space and time. This data set focuses on dietary overlap, with diet and predatory behaviour of wolf spiders (Lycosa spp.), the lesser hairy-footed dunnart (Sminthopsis youngsoni) and prowling spiders (Miturga spp., which represent other common invertebrate predators) were determined by tracking individuals and directly observing prey captures. Seventeen wolf spiders, 10 prowling spiders and 5 dunnarts were captured from Main Camp site in the Simpson Desert, south-western Queensland during 2016 with 30, 13 and 13 direct prey captures witnessed for each species respectively. This data is used for calculating overlap between prey taxa and prey size between these predators using the symmetrical version of MacArthur and Levin's and Pianka's overlap equation. However, it can also be used as a case study for calculating overlap between other species-groups.
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Purpose
The lesser hairy-footed dunnart (Sminthopsis youngsoni) is a common generalist insectivore in arid Australia that consumes wolf spiders (Lycosa spp.) disproportionately often relative to their availability. This study aimed to uncover the underlying mechanisms that drive this observed pattern of selective predation.
Lineage
Direct Observations: [1] Animal Trapping Individual S.youngsoni were live-captured in pitfall traps on 16 trapping grids located 0.62 km apart at Main Camp during July and October 2016. Each grid comprised 36 pitfall traps in a 6 × 6 formation with traps set 20 m apart. Grids encompassed all dune zones (crest, side and swale) and covered 1 ha. A trap consisted of a PVC pipe 60 cm deep × 16 cm diameter, dug flush with the sand surface and overlain by a 5 m long, 300 mm high drift fence of aluminium flywire to increase trapping efficiency. Captured individuals were identified, weighed, sexed and reproductive status checked, and then given a unique ear clip. Lycosid and miturgid spiders were collected opportunistically from vertebrate pitfall traps (see above) or through active searches over multiple nights at Main Camp. [2] Observations of Prey Capture Captured S.youngsoni were released and followed to directly observe their prey selection. After dusk, a small non-toxic glow stick, 4.5 mm diameter × 39 mm long (Neptune Tackle, Adelaide, South Australia) was activated before being secured to the hair of a dunnart from the nape down the back using non-toxic cyanoacrylate glue (Selley's Quick Fix superglue) and positioned so as not to impede head or leg movement. Distance of the observer to the dunnart varied depending on the microhabitats encountered, the speed of the dunnart, and the activity the dunnart was engaged in. Red light was used to illuminate dunnarts when foraging to facilitate identification of selected prey, minimise disturbance to their natural foraging behaviour, and to preserve each observer's night vision. Numbers, type and size of prey eaten were recorded, as well as time of night and method of prey capture. To quantify foraging and prey selection by lycosid and miturgid spiders, we scored the type and size of all prey items depredated during observations. Prior to release, a 3 × 3 mm square of silver reflective tape (Class 1 reflectivity, Seton Australia) was attached to the opisthosoma using non-toxic cyanoacrylate glue to increase the detectability of spiders when tracking them in low light conditions. Spiders were released near their capture site between 20:00 h and 23:00 h around Main Camp, and followed and observed for ~1 h under red torchlight at a distance of 3 m to minimise disturbance.
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