Dror Ben-Ami

The Effect of Road-Based Fatalities on the Viability of a Peri-Urban Swamp Wallaby Population

Abstract Roads and traffic have a multitude of impacts on wildlife populations. Wildlife existing within the confines of fragmented reserves are particularly susceptible to fatalities on roads, especially those situated within urban and semirural matrices. The sustainability of many wildlife populations within reserve fragments are tenuous as roads further subdivide reserved areas and increase the frequency of animal–vehicle contact. Although many studies have assessed the quantity and diversity of fatalities from collisions, few studies have examined the long-term viability of wildlife populations living adjacent to roads. We chose to examine the effects of disturbances, including fatalities on roads, on a population of swamp wallabies (Wallabia bicolor) within the Royal National Park on the urban fringe of Sydney, Australia. Despite having an extensive range, researchers suspect that many local populations of this sole member of Wallabia are in decline. We used a combination of population modeling and sensitivity analysis to assess the impact of disturbances on the population. Under current conditions, the forecast of the population was to decline over the next 100 years with the possibility of becoming extinct. We found that female reproduction and breeding were most influential on the population model. Of the range of management options investigated, by far the most rewarding was the reduction of fatalities on roads, as only a 20% decrease in female fatalities on roads has the potential to reverse the current decline and represents the best option for maintaining long-term viability. We suggest that documentation and subsequent management of road impacts, within the context of other threats, is essential to the conservation of similar species in road-affected environments.

Survival behaviour of swamp wallabies during prescribed burning and wildfire

Context.Prescribed(orcontrolled)burningisfrequentlyadvocatedasameansofreducingfuelloadsinperi-urbanforests to minimise the risk of high-intensity wildfires. An important consideration in prescribed burns is the impact on native wildlife. Aims. An opportunity arose to follow the movements of radio-collared peri-urban swamp wallabies during a prescribed burn and after an unexpected wildfire in the same location a short time later. Movement data was used to assess the relative impactsoftheprescribedburnandwildfireonmortality,emigrationandhabitatuse;thebehaviouralresponsesandmethods of avoidance used by swamp wallabies in response to an oncoming fire front; and the management implications for wildlife that inhabit fire-prone habitats in proximity to human settlement where wildfire mitigation is necessary. Methods. Here we report on the movements of radio-collared swamp wallabies, Wallabia bicolor, before, during and after a prescribed fire and after a wildfire on the same site 6 months later. Key results. No radio-collared swamp wallabies were killed during the prescribed burn and only one wallaby was observedtoemigratefromtheareapost-fire.Thiscontrastedtothewildfirewhereonewallabydiedduringorjustafterthe fire and another perished in the post-fire environment a few months later. The wildfire also increased emigration post-fire. Conclusions. We demonstrate that wallabies can avoid fire fronts and that this avoidance behaviour may be more successful during cooler fires. The prescribed burn provided a suitable habitat for wallabies but did not result in a shift in habitat preference. Implications. Mitigation of the impact of prescribed burns on swamp wallabies may be achieved by allowing sufficient time for habitat complexity to re-establish between burns.

The welfare ethics of the commercial killing of free-ranging kangaroos: An evaluation of the benefits and costs of the industry

The commercial killing of kangaroos provides multiple benefits to society, but also causes both deliberate and unintended harms to kangaroos. The ethics of the kangaroo industry is assessed in terms of whether the assumed benefits justify the welfare costs. An analysis of the stated benefits indicates that killing for damage mitigation is beneficial mainly during drought and not at current levels; that there is a commercial value, although considerably lower than previously estimated, and that demonstrable environmental benefits from commercial killing of kangaroos are lacking; and that the commercial kill may ameliorate the suffering of kangaroos during drought. Welfare practices are very difficult to assess and regulate due to the size and remote nature of the industry. A combination of empirical data on welfare outcomes and inferences drawn from behavioural and reproductive knowledge of the commercially killed species are utilised to assess harm. The welfare costs include deliberate and indirect harm to dependent young (a by-product of the commercial kill), and a number of unintended harms to adult kangaroos, including increased mortality during drought, inhumane killing of a portion of adult kangaroos, and a disruption of social stability and the evolutionary potential of individuals. Furthermore, a substantial gap exists between the intended welfare standards of the code of practice governing the kangaroo industry and the welfare outcomes for both dependent young and adult kangaroos. We found that, on balance, the benefits are lower than expected and the welfare costs are likely to be considerably higher than acceptable. More research, particularly at the point of kill, is necessary to verify and assess the extent of harms. A number of improvements are suggested to the code of practice to improve welfare outcomes.

Population viability assessment and sensitivity analysis as a management tool for the peri-urban environment

Anthropogenic disturbance occurring within urban ecosystems is often extreme and highly variable. A quantifiable measure of their effect on the persistence of urban wildlife populations would contribute to conservation efforts. This study suggests that population viability assessment, a commonly utilized modeling tool for creating management strategies for rare and threatened wildlife populations, is also appropriate in an urban context. It can be used to create proactive management strategies that quantify the impacts of anthropogenic disturbances and rank a range of management options within an active adaptive framework. To show this, population viability assessment and sensitivity analyses were run to forecast the population trends of a seemingly robust but isolated swamp wallaby (Wallabia bicolor) population living in peri-urban Sydney, Australia; a population exposed to anthropogenic disturbances from towns, hobby farms and roads. Modeling suggested this population was in a slow decline and that predictions were highly dependent upon stochastic events and the precision of reproduction rates. However, a number of management options are identified that will dramatically reduce the risk of total population decline, with complementary options utilized in tandem the most effective.

Impact of roadside habitat on swamp wallaby movement and fitness

Abstract Context. Roads have numerous impacts on wildlife populations, such as forming barriers to movement and isolating them from resources. However, knowledge of how wildlife behave in road-impacted environments is limited. Aims. Our aim was to assess the suitability of roadside habitat for the swamp wallaby (Wallabia bicolor). Methods. We measured the home range, habitat use and body metrics of swamp wallabies at two roadside locations. The home ranges and fitness of the roadside wallabies were compared with the metrics of swamp wallabies within the adjacent reserve. Key results. The roadside wallabies had a preference for canopy cover, but not for other habitat features. The roadside home ranges were stable and relatively small. The nocturnal ranges were considerably smaller and further from the road than were diurnal ranges. Only one wallaby crossed the road during the study, via an underpass. There was a significant positive linear correlation between pes length and bodyweight. Roadside wallabies were significantly heavier than were reserve wallabies. Conclusions. Our study suggested that individual wallabies avoid the road, are habituated to the roadside environment and may even benefit from it. At the very least, roadside habitats are adequate for the swamp wallaby. Implications. Fencing and road crossings are likely to be beneficial conservation-management measures for swamp wallabies in roadside reserves.