Long-term spatiotemporal dynamics and factors associated with trends in bare-nosed wombats

Geographically widespread species present challenges for conservation assessment. We used long-term spotlight surveys to assess spatiotemporal dynamics of bare-nosed wombats (Vombatus ursinus), encompassing 34 years of surveys for the Tasmanian mainland sub-species (V. u. tasmaniensis, 1985-2018) and 25 years for the Flinders Island sub-species (V. u. ursinus, 1994-2018). Wombat populations increased on the Tasmanian mainland by 2.59 times and on Flinders Island by 3.51 times (x̄ = 1.05 and 1.1 times increase/yr, respectively). At smaller spatial scales on mainland Tasmania, increases in wombat counts generally occurred within meteorological regions and regional zones, except for the Central North (West Tamar) region where a decrease in wombats is linked to a sarcoptic mange disease epizootic. We used generalized additive models to assess relationships between variables and wombat counts. The most supported variables at the mainland Tasmania scale were (in order of importance) year, positive associations with time-lagged minimum temperature, Tasmanian devil (Sarcophilus harrisii) counts, and moonlight, and a negative association with time-lagged rainfall. Among meteorological regions, variables associated with wombat counts exhibited some heterogeneity, with temperature and rainfall the most frequently associated variables. Our long-term, large-scale, and ecologically diverse analysis of bare-nosed wombats supports spotlight monitoring as a valuable, relatively simple, and affordable survey method in Tasmania and beyond.