University of Tasmania
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Aspects of the feeding ecology of the Bandicoots, Perameles gunnii (GRAY 1838) and Isoodon obesulus (Shaw and Nodder 1797) (Marsupialial peramelidae) in southern Tasmania

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posted on 2023-05-27, 08:43 authored by Quin, DG
An investigation was undertaken into the diet and comparative feeding ecology of the Tasmanian Bandicoots, Perameles gunnii and Isoodon obesutus affinis. Studies on captive specimens revealed that both P. gunnii and I. obesutus detected significantly more cups containing ground cockroach extract than non-extract cups buried at various depths. However, only P. gunnii located significantly more cups containing earthworm extract than non-extract cups. Auditory trials demonstrated that P. gunnii and I. obesutus do not appear to depend on hearing to locate prey. Olfaction appears to be the primary prey detection strategy employed by bandicoots. Digestibility trials revealed that soft-bodied prey such as earthworms may be totally digested, hence they appear absent in bandicoot faeces. Soft-bodied insects e.g. cockroaches, although identifiable in faeces, are difficult to quantify due to the digestive fragmentation of potentially quantifiable structures. From their diet in southern Tasmania, P.gunnii and I. obesutus appear to be qualitatively opportunistic omnivores, feeding on a wide range of prey available, but apparently not always in proportion to which they occur. The overlap in 36 prey categories is positively correlated for each of the Peramelids with only two taxa showing significant differences in the total diets between the two species. Significantly more I. obesutus scats than P. gunnii samples were collected containing bees and wasps (Hymenoptera); significantly more P. gunnii faeces were obtained containing Clover (Trifolium repens). The diet would largely appear to reflect seasonally and locally abundant food items. The most important dietary items for I. obesutus in autumn appeared to be ants (Formicidae), maggots (Calliphoridae larvae), Rove beetles (Staphylinidae), mature Coleopterans, Scarabaeidae larvae, Hymenopterans and Hemipterans, while those of P. gunnii were larvae, spiders (Araneae), flies (mature Diptera), Calliphoridae larvae, ants, ground beetles (Carabidae) and their larvae. Blackberries, Monocot and a Zygomycete fungus were important plant components in faecal pellets of both species, and Moss and nodules in P. gunnii. Two faecal pellets in winter for P.· gunnii revealed Scarabaeidae larvae, Calliphoridae larvae, armyworms (Noctuidae), Springtails (Collembola) in half of the sample while Clover root nodules and seeds occurred in both scats. In I. obesulus, Scarabaeidae larvae, ants, Carabidae larvae, mature Coleoptera, seeds, Monocot, nodules and Gasteromycete fungus occurred in more faecal pellets for the winter session than other prey taxa. In spring, a marked increase in E/S/C larvae correlated with an increase in this category in the faeces of both bandicoot species. Corbie grubs (Hepialidae), spiders, Rove beetles, Monocot, seeds and Clover root nodules occurred in more scats of I. obesu'lus, relative to other taxa. For P; gunnii, armyworms appeared to be most important with larvae, Mites (Acarina), Scarabaeidae larvae, mature Coleoptera, Monocot, seeds and roots. Slight diet differences were observed between habitats for I. obesulus and appeared to reflect the local availability of prey items. Prey size selection indicated that I.obesulus and P; gunnii appear to take a similar size of prey (approximately 11-11.5 mm); however the number of samples recorded for P; gunnii was small: No correlation appeared to exist between predator weight (I. obesulus) and mean prey size as determined by regression equations relating insect tarsal widths from faeces to those of insects of a known length. Bimodal capture-success-curves were recorded for I. obesulus possibly due to the inclusion of elongate Rove beetles and small prey (1-2 and 2-3 1 in winter) when larger prey appeared to decrease in availability. However, I; obesulus predominantly selected larger size classes of prey than those available. Diet does not seem to be a significant factor in the apparent spatial, ecological separation exhibited by the two Peramelid species. Temporal segregation may be additionally important in reducing competition between I. obesulus and P. gunnii.


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