A Trial of a Virtual Fence to Mitigate Roadkill on an Unsealed Rural Road in Tasmania, Australia

Simple Summary Simple Summary: Roadkill of native animals, particularly marsupials, is a serious problem for wildlife conservation, animal welfare, and tourism in Tasmania, so any proposed method that substantially reduces native marsupial roadkill, while being cost-effective, deserves a thorough scientific evaluation. A commercial roadkill Virtual Fence (VF) mitigation device was evaluated using a repeat of a similar trial in southern Tasmania in 2018. The same VF installation and experimental designs were employed over a similar length of road (4.9 km versus 4.5 km), with the current trial having a substantially longer period of monitoring (i.e., 585 d versus 126 d). Sections of the virtual fence were switched on or off according to the same predetermined experimental design. Tasmanian pademelons were the most commonly killed species, at 222, over the total trial period, while 47 Bennett's wallabies were killed. The kill rate for the three spatial replicates and two monitoring periods (a total of 110 pademelons killed over 221 d) when the VF was switched off versus the periods when it was switched on were 3.35 and 3.33 month-1km-1, respectively. The corresponding rates for the total of 19 Bennett's wallabies that were killed were 0.55 and 0.61. Analyses of pademelons, which included pre-on and post-on periods for comparison, failed, as in the 2018 trial, to demonstrate any statistically significant effect of the virtual fence in reducing roadkill for this species.Abstract A commercial roadkill Virtual Fence (VF) mitigation device (iPTE Traffic Solutions) was used in a field trial to test its effectiveness, for which previously published results have been inconsistent, along a 4.9 km segment of road on Bruny Island, Tasmania. A total of 585 days of monitoring roadkill by species was conducted, with six sections that were alternatively switched on or off according to the Crossover and Multiple Before-After-Control-Impact (MBACI) experimental designs that divided monitoring into "off-on" then "on-off" periods. Aggregate counts, for each period by section combination, from daily counts of Tasmanian pademelons (Thylogale billardierii) were modelled, with a total count of 222. The statistical analysis used the MBACI design to estimate the VF effect using a log-odds ratio parameter (LORP) while accounting for local spatio-temporal effects. Both versions of the analysis, either averaged over the three spatial replicates (paired sections) or two temporal replicates (blocks), showed no statistically significant effect of the VF, judged as an LORP estimate not sufficiently below zero. Corresponding percentage reduction estimates of 9% and 16% were derived from the LORP. The corresponding statistical power required to detect a nominal significant reduction of 50% in rate was 0.5 and 0.6, respectively. This study confirms the results from a similar previous field trial in southern Tasmania that this VF is likely to lead to, if anything, only a minor reduction in roadkill.