Simple SummaryThe Australian state of Tasmania has a high rate of roadkill, so any method that reduces roadkill in this state deserves attention. A commercial roadkill mitigation device, which combines an auditory warning signal with flashing blue and amber lights in linked units to form a so-called virtual fence, is said to reduce roadkill by up to 90%. For the current trial, a virtual fence was installed on a 4.5-km segment of Tasmanian highway south of Hobart and roadkill was monitored on a daily basis for a period of 126 days. Sections of the virtual fence were switched on or off, according to a predetermined experimental design. Bennett’s wallabies, Tasmanian pademelons, and common brush-tail possums accounted for most of the total roadkill of 174 animals over the study period. For these three species, four complementary methods of analysis failed to reveal any significant effect of the virtual fence in reducing roadkill. This study does not confirm previously reported estimates of reduction in roadkill rates of 50%–90%.AbstractWhen wildlife and motor vehicles collide, the result for the animals is often death (roadkill). A commercial roadkill mitigation device that forms a so-called virtual fence (VF), is said to reduce roadkill by up to 90%. A field trial to test its effectiveness was undertaken along a 4.5-km segment of a Tasmanian highway subdivided into 6 equal sections. A total of 126 days of monitoring of roadkill by species was conducted, with alternate sections being switched on or off, according to a variation of Crossover and Multiple Before-After-Control-Impact experimental designs that divided monitoring into five periods. From the six sections over the five periods, the 30 aggregated values of daily counts of roadkill for each species were modelled. Bennett’s wallabies (BW) (Notamacropus rufogriseus), Tasmanian pademelons (TP) (Thylogale billardierii) and common brush-tail possums (BP) (Trichosurus vulpecula) accounted for most of the total roadkill of 174 animals. Although initially there appeared to be an effect, linear model fits to standardised roadkill rates were not statistically significant for each of BW, TP, and BP using each of the Crossover, Multiple Before-After-Control-Impact, and simple On versus Off comparisons. Adjustment for spatial and temporal trends using a Generalised Additive Model with Poisson error also failed to detect a significant VF effect. A simulation study used to estimate the power to detect a statistically significant reduction in roadkill rate gave, for median estimates of reduction of 21%, 48%, and 57%, estimates of power of 0.24, 0.78, and 0.91, respectively. Therefore, this study failed to confirm previously reported estimates of reduction in roadkill rates claimed for this VF of 50%–90%, despite having adequate power to do so. However, point estimates obtained for these three species of reductions ranging from 13% to 32% leave open the question of there being a real but modest effect that was below statistical detection limits.
The non-human animal deaths and injuries that result from collisions with motor vehicles are known colloquially as roadkill, and often lead to individuals from various taxa being orphaned. The complexities of multiple spatial and temporal variables in the available data on Australian roadkill and the scale of orphaning and injury make statistical analysis difficult. However, data that offer proxy measures of the roadkill problem suggest a conservative estimate of 4 million Australian mammalian roadkill per year. Also, Australian native mammals are mainly marsupial, so female casualties can have surviving young in their pouches, producing an estimated 560 000 orphans per year. A conservative estimate is that up to 50 000 of these are rescued, rehabilitated and released by volunteer wildlife carers. These roadkill-associated orphans are in addition to those produced by other anthropogenic and natural events and the injured adult animals in the care of volunteers. In accepting total responsibility for rescued animals, wildlife carers face many demands. Their knowledge base can require days of initial instruction with the need for continual updates, and their physical abilities and personal health can be tested by sleepless nights, demanding manual tasks and zoonoses. This review article explores the impact of this commitment and conservatively estimates carers’ financial input to raise one joey at approximately $2000 a year, and their time input at 1000 h, equating to $31 000 per year, applying a dollar value of $31 per hour. It categorises relevant types of grief associated with hand-rearing orphans and rehabilitating injured animals, and suggests that wildlife carers most likely experience many types of grief but are also susceptible to burn-out through compassion fatigue. A perceived lack of understanding, empathy and appreciation for their work by government can add to the stressors they face. Volunteering is declining in Australia at 1% per year, social capital is eroding and the human population is aging, while the number of injured and orphaned animals is increasing. Wildlife carers are a strategic national asset, and they need to be acknowledged and supported if their health and the public service they provide is not to be compromised.
The Australian constitution makes no mention of native animals. Responsibility for animal welfare is largely retained by the states and territories via a fragmented, complex, contradictory, inconsistent system of regulatory management. Given that most jurisdictions have expressly made the possession of wildlife unlawful, the action of taking and possessing an animal, to rehabilitate it, defies the regulatory process. In most jurisdictions, it is illegal to microchip, band, or mark an animal, meaning that no reliable method is available to monitor an animal. Each year, a minimum of 50,000 rehabilitated native animals are released back to the wild, with little post-release monitoring. Where required, the assessments of behavioural and health requirements to confirm suitability for release may be undertaken by people with either negligible or questionable qualifications. Whilst it can be appropriate to rehabilitate and release injured native animals back to the wild, there may be moral, ethical, and practical reasons for not releasing hand-reared orphan native animals. This article examines the evolution, and explains the consequences, of decentralised regulation on wildlife carers and rehabilitating animals. It recommends that the practice of placing hand-reared native animals into the wild, and the regulatory framework that provides for it, should be reviewed.
The rescue, rehabilitation and release of injured and orphaned Australian wildlife is managed by over 20,000 carers, mostly voluntarily. These volunteers experience mental, physical and financial challenges that have not been researched adequately. This study collated the responses (n = 316) to a survey conducted among Australian wildlife carers who actively foster orphaned joeys for hand-raising and injured adult mammals for rehabilitation and release. It confirmed 86% of rehabilitators are female, 70% are over the age of 46 years and their prime motivation is an affinity with animals. The average time spent in the sector is 11.5 years, and the work week is 31.6 h, caring for 15 animals per year, with an average of 2.6 dying. The average financial commitment is AUD5300 annually and up to AUD800,000 over a lifetime. Regarding the grief experienced by carers, the lower the age, the longer the time spent, the greater the financial input and the more joeys that died, the more severe is the grief experienced. Moderate to severe grief is experienced by 28% of carers, which, coupled with other factors, could lead to burnout or compassion fatigue. Soon, wildlife carer welfare will likely be compromised unless financial and mental support is provided and their workload reduced.
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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