Can virtual fences reduce wombat road mortalities?

Stannard, Hayley J.; Wynan, Marie B.; Wynan, Ray J.; Dixon, Brendan A.; Mayadunnage, Sujatha; Old, Julie M

doi:10.1016/j.ecoleng.2021.106414

Cited by 5 publications

(20 citation statements)

References 24 publications

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“…In order to provide some sense of the statistical significance of the results of monitoring roadkill in the BACI trial of Stannard et al [12] we used their published data to fit a Poisson generalized GLM to the above 2x2 table of raw counts. Without spatial or temporal replication given that only a single 2x2 table of counts was available for estimation, it was necessary to assume a pure Poisson process generated the counts in order to estimate the uncertainty of the estimated effect of the VF.…”

Section: Experimental Design Materials and Methodsmentioning

confidence: 99%

“…We used the data given in the Stannard et al [12] (see Table 1 below) to fit a Poisson generalized linear model (GLM) with log link function [14] to the 2x2 table of raw counts with the corresponding monitoring periods expressed on a log scale as an "offset" (see Appendix) which effectively converts raw counts to period standardised rates. Taking into account main effects given by 2-level factors defined as "site" (i.e.…”

Section: Experimental Design Materials and Methodsmentioning

confidence: 99%

“…Further, a simulation study they carried out confirmed the study design had a .78 power to detect a reduction of the order of 48%. Stannard et al [12] correctly quote the above point estimates of percentage reduction in rates due to the VF in the discussion of their paper but in their introduction contradict this correct result by claiming "Englefield et al (2019) found that roadkill rates were reduced by 21 to 57% depending on species". This incorrect interpretation was also noted by Coulson and Bender [13].…”

Section: Introductionmentioning

confidence: 98%

“…Stannard et al [12] did not estimate a percentage reduction but presented a monthly rate for bare-nosed wombats (Vombatus ursinus) for the study 1.5 km fenced road section of 0.7 month -1 for the 995 days of monitoring before VF installation and 0.6 month-1 for the 322 days of monitoring after installation. Their study design is an unreplicated BACI design.…”

Section: Introductionmentioning

confidence: 99%

“…The debate on the utility or otherwise of this technology for mitigating wildlife roadkill needs a scientifically robust literature by considering, among other important issues, the necessity for valid statistical inferences [9]. To this end we emphasis in this commentary the validity of experimental designs and associated statistical inference that have been applied and provide a statistical inference procedure using the data given in Stannard et al [12]. We also provide an assessment of the statistical power of this unreplicated BACI design, given the observed overall roadkill rates, to detect a hypothetical effect of a 50% reduction in rate using simulation to replicate the 2x2 table.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of Roadkill Rates from a Trial of a Virtual Fence for Reducing Wombat Road Mortalities. Are Severely Under-Powered Studies Worth the Effort?

Candy¹,

Englefield²

2022

CJAST

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Aims: Evaluation of the effectiveness of methods of roadkill mitigation requires field experiments and thus experimental designs. We evaluated such a published experiment that used a virtual road-fence (VF) system to attempt to reduce roadkill of bare-nosed wombats (Vombatus ursinus) and draw general conclusions on the ability of the implemented design, given overall mean rates of roadkill, to detect a substantial reduction of 50%. Study Design:The study site consisted of contiguous fenced and unfenced road sections that were each monitored for road kill for 995 and 322 days pre-and post-installation, respectively. The study design was an unreplicated BACI (Before-After-Control-Impact) design. Methodology: No statistical analysis of the roadkill data were carried out in the original study. We used a Poisson/log-link Generalized Linear Model fit to their BACI data as a single 2x2 table of counts and define a single interaction parameter as a function of control-adjusted rate reduction due to the VF. This parameter can also be defined as the logarithm of the ratio of odds of a random kill in the fenced section occurring in the post-installation period to the corresponding odds for the unfenced section. A null hypothesis of no effect of the VF corresponds to a log odds-ratio of zero. We use simulation to show that estimates of this parameter have close to a Gaussian distribution and from this derive an estimate of the statistical power of the design to detect a hypothetical effect Method Article

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Section: Experimental Design Materials and Methodsmentioning

confidence: 99%

Section: Experimental Design Materials and Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Analysis of Roadkill Rates from a Trial of a Virtual Fence for Reducing Wombat Road Mortalities. Are Severely Under-Powered Studies Worth the Effort?

Candy¹,

Englefield²

2022

CJAST

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The Distinctive Biology and Characteristics of the Bare-Nosed Wombat (Vombatus ursinus)

Carver,

Stannard,

Martin

2024

Annu. Rev. Anim. Biosci.

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The bare-nosed wombat is an iconic Australian fauna with remarkable biological characteristics and mythology. This solitary, muscular, fossorial, herbivorous marsupial from southeast Australia has continent and continental island subspeciation. Vombatiformes also contains hairy-nosed wombats ( Lasiorhinus spp.); koala ( Phascolarctos cinereus); and extinct megafauna, Phascolonus gigas (giant wombat), Diprotodon, and Thylacoleo (marsupial lion). Culturally important to Aboriginal people, bare-nosed wombats engineer ecosystems through digging, grazing, and defecation. Olfaction and cubic fecal aggregations appear critical for communication, including identity, courtship, and mating. Though among the largest fossorial herbivores, they have a nutrient-poor diet, a home range up to an order of magnitude smaller than expected, and a metabolism among the lowest extreme for mammals >10 kg. Metabolic depression may confer advantages over resource competitors and fossorial lifestyle protection from predators, fires, and climatic extremes. Bare-nosed wombats are loved and persecuted by European colonists. Recent population increases may reflect softening attitudes toward, and greater protections of, bare-nosed wombats. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 12 is February 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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Another Trial of a Solar-Powered, Cooperative Sensor/Actuator, Opto-Acoustical, Virtual Road-Fence to Mitigate Roadkill in Tasmania, Australia

Candy,

Bunker,

Englefield

2024

Preprint

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When wildlife and motor vehicles collide, the result for the animals is often death (roadkill). A commercial roadkill Virtual Fence (VF) mitigation device (iPTE Traffic Solutions) was used in a field trial to test its effectiveness along a 4.9-km segment of road on Bruny Island, Tasmania. A total of 585 days of monitoring of roadkill by species was conducted, with six sections alternatively switched on or off, according to a variation of a Crossover and Multiple Before-After-Control-Impact (MBACI) experimental designs that divided monitoring into “off-on” then “on-off” blocks of periods with each “on” period followed by a 16 d “wash-out” period. For the six sections over the four periods that exclude wash-outs, the 24 aggregated values of daily counts of roadkill of Tasmanian pademelons (Thylogale billardierii), that gave a total count of 222, were modelled. Other species were killed in insufficient numbers for analysis to be informative. The statistical analysis exploited 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 averaging over the three spatial replicates (paired sections) or two temporal replicates (blocks) gave no statistically significant effect of the VF judged as a LORP estimate not sufficiently below zero. Corresponding percentage reduction estimates of 9% and 16% were derived from the LORP estimates and given parameter uncertainty estimates the power to detect as significant a LORP corresponding to a 50% reduction in rate were 0.5 and 0.6, respectively. This study confirms results from a similar field trial carried out in 2018 also in southern Tasmania and adds to the evidence that this VF is likely to give if anything only a minor reduction in roadkill for a commonly killed species for which researchers have the best chance of detecting any practically useful reduction.

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Can virtual fences reduce wombat road mortalities?

Cited by 5 publications

References 24 publications

Analysis of Roadkill Rates from a Trial of a Virtual Fence for Reducing Wombat Road Mortalities. Are Severely Under-Powered Studies Worth the Effort?

Analysis of Roadkill Rates from a Trial of a Virtual Fence for Reducing Wombat Road Mortalities. Are Severely Under-Powered Studies Worth the Effort?

The Distinctive Biology and Characteristics of the Bare-Nosed Wombat (Vombatus ursinus)

Another Trial of a Solar-Powered, Cooperative Sensor/Actuator, Opto-Acoustical, Virtual Road-Fence to Mitigate Roadkill in Tasmania, Australia

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