Ben-Ami, D, Ramp, D & Croft, DB 2006, 'Population viability assessment and sensitivity analysis as a management tool for the peri-urban environment', Urban Ecosystems, vol. 9, no. 3, pp. 227-241.
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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.
Klocker, U, Croft, DB & Ramp, D 2006, 'Frequency and causes of kangaroo-vehicle collisions on an Australian outback highway', WILDLIFE RESEARCH, vol. 33, no. 1, pp. 5-15.
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Kangaroo-vehicle collisions are frequent on Australian highways. Despite high economic costs, detrimental effects on animal welfare, and potential impacts on population viability, little research has been done to investigate the impact of road mortality on kangaroo populations, where and why accidents occur, and how the collisions can be mitigated. We therefore collected data on species (Macropus rufus, M. giganteus, M. fuliginosus, M. robustus), sex and age of kangaroos killed on a 21.2-km bitumenised section of outback highway over 6 months in far western New South Wales, Australia. The spatial and temporal distribution of road-killed kangaroos was investigated in relation to the cover and quality of road-side vegetation, road characteristics, the density of kangaroos along the road, climatic variables and traffic volume. A total of 125 kangaroos were found killed on the road at a rate of 0.03 deaths km-1 day-1. Grey kangaroos of two species (M. giganteus, M. fuliginosus) were under-represented in the road-kill sample in comparison with their proportion in the source population estimated during the day. No bias towards either sex was found. The age structure of road-killed kangaroos was similar to age structures typical of source kangaroo populations. Road-kills mainly occurred in open plains country. In road sections with curves or stock races, road-kill frequencies were higher than expected. Greater cover and greenness of roadside vegetation at the verge probably attracted kangaroos to the road and variation in this vegetation affected the spatial distribution of road-kills. The temporal distribution of road-kills was positively correlated with the volume of night-time traffic. The probability of a kangaroo-vehicle collision increased exponentially with traffic volume. Results are discussed in relation to the potential for mitigation of kangaroo-vehicle collisions. © CSIRO 2006.
Maguire, G, Ramp, D & Coulson, G 2006, 'Foraging behaviour and dispersion of eastern grey kangaroos (Macropus giganteus) in an ideal free framework', JOURNAL OF ZOOLOGY, vol. 268, no. 3, pp. 261-269.
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Ideal free distribution (IFD) theory predicts that animals in competitive situations should distribute themselves among available habitat patches according to the density of conspecifics and its regulatory effect on resources. To investigate the applicability of IFD models to free-ranging herbivores, we quantified the dispersion and foraging behaviour of eastern grey kangaroos Macropus giganteus among habitat patches of differing suitability, within and outside a reservoir catchment in southern Victoria, Australia. Kangaroo densities within the catchment had a regulatory effect on resource density, while surrounding farmland maintained a higher standing crop despite higher densities of competitors. This difference was slight in autumn, however, when the system was apparently close to equilibrium. Gross bite rates of individuals foraging in farmland were lower than for individuals foraging within the catchment, and vigilance behaviour occurred more frequently in farmland habitat than any other, decreasing time devoted to feeding. Interference competition occurred in only 1.9% of focal samples, although competitive differences based on phenotype were observed. Although resource gains by individual kangaroos are likely to be influenced by other factors, including resource dynamics, predation risk and phenotypic differences, IFD theory provides a valuable analytical framework for this herbivore foraging system. © 2006 The Zoological Society of London.
Ramp, D & Ben-Ami, D 2006, 'The effect of road-based fatalities on the viability of a peri-urban swamp wallaby population', JOURNAL OF WILDLIFE MANAGEMENT, vol. 70, no. 6, pp. 1615-1624.
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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.
Ramp, D & Croft, DB 2006, 'Do wildlife warning reflectors elicit aversion in captive macropods?', WILDLIFE RESEARCH, vol. 33, no. 7, pp. 583-590.
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A goal to reduce the frequency of animal-vehicle collisions is motivating extensive research on this topic world-wide. Over the last 30 years, one popular mechanism to warn wildlife of approaching vehicles has been the wildlife warning reflector, manufactured and distributed under the brands Swareflex (Austria) and Strieter-Lite (USA). These reflectors were designed to scare deer and other ungulates from roadways at night by reflecting light from the headlights of approaching vehicles into the eyes of animals on the road verge. Robust documentation of their effectiveness has been lacking, yet there has been a push in Australia to examine their efficacy with regard to medium to large macropodids. Field trials of the reflectors are problematic and difficult to design rigorously, so we chose to examine the behavioural response of two captive macropodid species (Macropus rufus and M. rufogriseus) to the reflectors on a simulated road in order to derive some indication as to their efficacy. The behavioural response to the reflectors was negligible for both species and not consistent with an aversive effect to deter road use or crossing. We conclude that they would be of little value in our efforts to reduce the frequency of collisions of kangaroos or wallabies with vehicles in Australia. © CSIRO 2006.
Ramp, D, Wilson, VK & Croft, DB 2006, 'Assessing the impacts of roads in peri-urban reserves: Road-based fatalities and road usage by wildlife in the Royal National Park, New South Wales, Australia', BIOLOGICAL CONSERVATION, vol. 129, no. 3, pp. 348-359.
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For protected reserves set aside for conservation, the impact of roads and traffic on wildlife can be severe, particularly for those in the peri-urban environment. Often reserves possess many sealed roads that have regular traffic from tourists and local residents. As managerial bodies struggle to control the wide variety of threats to the fauna within these reserves, the loss of life on roads only compounds the precarious nature of wildlife survival in these disturbed environments. As a first step to addressing this concern in Australia, this study quantifies the fatalities of wildlife killed on roads within the Royal National Park in New South Wales, and estimates those wildlife species using roadside habitat in order to identify species susceptible to collisions. Modelling of fatality data indicated that mammals were most likely to be killed where forage was abundant on the roadside verge and where there was plenty of protective cover, while birds were most likely to be killed when the height of roadside vegetation was low. A number of collision hotspots were identified along the surveyed road that should be the target of mitigation efforts. The average speed of vehicles travelling within the park peaked at night. This is of particular concern as activity by Australian mammals tends to be greatest at night. The findings indicate that roads in peri-urban reserves have the potential to alter the movement of animals and impact on their populations through loss of life. © 2005 Elsevier Ltd. All rights reserved.
Rose, TA, Munn, AJ, Ramp, D & Banks, PB 2006, 'Foot-thumping as an alarm signal in macropodoid marsupials: prevalence and hypotheses of function', MAMMAL REVIEW, vol. 36, no. 4, pp. 281-298.
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1. Alarm signalling as a means to reduce predation risk is an important component of the behavioural repertoire of many species. It has previously been noted that many of the macropodoid marsupials (kangaroos, wallabies and rat-kangaroos) produce a foot-thump, an audible signal created by striking the ground with one or both feet, that is most likely an alarm signal. 2. The prevalence of foot-thumping within the macropodoids and hypotheses of its function as an alarm signal have been poorly documented. To address this issue, we investigate the prevalence of foot-thumping in macropodoids and interpret possible function according to current alarm signalling theory. Evidence for foot-thumping was found in almost all macropodoids. In light of this, the behaviour appears to be a conservative trait that may have arisen alongside or followed the evolution of bipedal locomotion, and suggests that this trait carries significant benefits that transcend ecological and predation differences among species. 3. Nine alarm signal hypotheses were explored in order to determine the function of foot-thumping in macropodoid marsupials. However, the existing evidence for consistent function remains inconclusive. Therefore, a series of predictions were developed to provide the foundation for future research to investigate more thoroughly the function of foot-thumping in macropodoid marsupials. © 2006 The Authors; Journal compilation © 2006 Mammal Society.
