Thersites mitchellae (Cox, 1864) (Camaenidae) is a regionally endemic Australian land snail that is critically endangered under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). We studied its habitat use and movement patterns. Knowledge of habitat use is relevant to the conservation of the species, and knowledge of movements is relevant to the interpretation of the results of capture-recapture studies and occupancy-based habitat models. We provide quantitative data of nightly distances travelled, the probability of moving on a night, retreat site selection, overnight substrate use and activity. A total of 636 location positions for 11 snails was recorded on 12 nights over an 18-day period. Nocturnal movements measured at approximately 2-hour intervals showed that the mean nightly movement was 457.8 cm. The maximum nightly movement by an individual was 1,575 cm, and the maximum nightly displacement was 1,270 cm. Over the study period, the maximum movement from capture was 74.45 m, and the maximum displacement was 31.80 m. The results show that the probability of moving on a night, and the nightly distance moved once active both increase with increasing humidity up to a maximum and then decline. Whilst individuals did not return to the same retreat site location with any reliability, there is evidence of active and frequent selection of particular retreat site types within selected habitats. Snails most frequently selected sedge retreat in rainforest (66.7%) and in paperbark wetland (59.3%), and despite the scarcity of sedge in palm forest, it was the most frequented retreat site group overall (42.5%). Snails selected palm frond retreats most frequently in the palm forest (66.7%), and coarse woody debris (CWD) was selected in all habitats (17.9%) and most frequently in the palm forest (27.8%). Statistical analysis revealed significant variation among individuals in their relative use of retreat site types, and significant association between the selection of retreat site types and the initial habitat in which the individuals were located.
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Vol. 57 • No. 2