Ecology of arboreal marsupials in a network of remnant linear habitats

Linear strips of vegetation set within a less-hospitable matrix are common features of landscapes throughout the world. Depending on location, form and function, these linear landscape elements include hedgerows, fencerows, shelterbelts, roadside or streamside strips and wildlife corridors. In many anthropogenically-modified landscapes, linear strips are important components for conservation because they provide a large proportion of the remaining wooded or shrubby habitat for fauna. They may also function to provide connectivity across the landscape. In some districts, the linear strips form an interconnected network of habitat. The spatial configuration of remnant habitat (size, shape and arrangement) may influence habitat suitability, and hence survival, of many species of plant and animal in modified landscapes. Near Euroa in south-eastern Australia, the clearing and fragmentation of temperate woodlands for agriculture has been extensive and, at present, less than 5% tree cover remains, most of which (83%) occurs as linear strips along roads and streams. The remainder of the woodland occurs as relatively small patches and single isolated trees scattered across the landscape. As an assemblage, arboreal marsupials are woodland dependent and vary in their sensitivity to habitat loss and fragmentation. This thesis focusses on determining the conservation status of arboreal marsupials in the linear network and understanding how they utilise the landscape mosaic. Specifically, the topics examined in this thesis are: (1) the composition of the arboreal marsupial assemblage in linear and non-linear woodland remnants; (2) the status and habitat preferences of species of arboreal marsupial within linear remnants; and (3) the ecology of a population of the Squirrel Glider Petaurus norfolcensis in the linear network, focusing on population dynamics, spatial organisation, and use of den trees. The arboreal marsupial fauna in the linear network was diverse, and comprised seven out of eight species known to occur in the district. The species detected within the strips were P. norfolcensis, the Sugar Glider Petaurus breviceps, Common Brushtail Possum Trichosums vulpecula, Common Ringtail Possum Pseudocheirus peregrinus, Brush-tailed Phascogale Phascogale tapoatafa, Koala Phascolarctos cinereus and Yellow-footed Antechinus Antechinus flavipes. The species not detected was the Feathertail Glider Acrabates pygmaeus. Survey sites in linear remnants (strips of woodland along roads and streams) supported a similar richness and density of arboreal mammals to sites in non-linear remnants (large patches or continuous tracts of woodland nearby). Furthermore, the combined abundance of all species of arboreal marsupials was significantly greater in sites in the linear remnants than in the non-linear remnants. This initial phase of the study provided no evidence that linear woodland remnants support a degraded or impoverished arboreal marsupial fauna in comparison with the nonlinear remnants surveyed. Intensive trapping of arboreal marsupials within a 15 km linear network between February 1997 and June 1998 showed that all species of arboreal marsupial (except A. pygmaeus) were present within the linear strips. Further analyses related trap-based abundance estimates to measures of habitat quality and landscape structure. Width of the linear habitat was significantly positively correlated with the combined abundance of all arboreal marsupials, as well as with the abundance of P. norfolcensis and T. vulpecula. The abundance of T. vulpecula was also significantly positively correlated with variation in overstorey species composition, Acacia density and the number of hollow-bearing trees. The abundance of P. norfolcensis was positively correlated with Acacia density and canopy width, and negatively correlated with distance to the nearest intersection with another linear remnant. No significant variables were identified to explain the abundance of P. tapoatafa, and there were insufficient captures of the remaining species to investigate habitat preferences. Petaurus norfolcensis were resident within the linear network and their density (0.95 -1.54 ha-1) was equal to the maximum densities recorded for this species in continuous forest elsewhere in south-eastern Australia. Rates of reproduction were also similar to those in continuous forest, with births occurring between May and December, a mean natality rate of 1.9, and a mean litter size of 1.7. Sex ratios never differed significantly from parity. Overall, the population dynamics of P. norfolcensis were comparable with published results for the species in contiguous forest, clearly suggesting that the linear remnants currently support a self-sustaining, viable population. Fifty-one P. norfolcensis were fitted with radio transmitters and tracked intermittently between December 1997 and November 1998. Home ranges were small (1.3 - 2.8 ha), narrow (20 - 40 m) and elongated (322 - 839 m). Home ranges were mostly confined to the linear remnants, although 80% of gliders also utilised small clumps of adjacent woodland within farm paddocks for foraging or denning. Home range size was significantly larger at intersections between two or more linear remnants than within straight sections of linear remnants. Intersections appeared to be important sites for social interaction because the overlap of home ranges of members of adjacent social groups was significantly greater at intersections than straight sections. Intersections provided the only opportunity for members of three or more social groups to interact, while still maintaining their territories. The 51 gliders were radiotracked to 143 different hollow-bearing trees on 2081 occasions. On average, gliders used 5.3 den trees during the study (range 1-15), and changed den trees every 4.9 days. The number of den trees used by each glider is likely to be conservative because the cumulative number of den trees continued to increase over the full duration of the study. When gliders shifted between den trees, the mean distance between consecutive den sites was 247 m. Den trees were located throughout a glider's home range, thereby reducing the need to return to a central den site and potentially minimising energy expenditure. Dens were usually located in large trees (mean diameter 88.5 cm) and were selected significantly more often than expected based on their occurrence within the landscape. The overall conclusion of this thesis is that the linear network I studied provides high quality habitat for resident populations of arboreal marsupials. Important factors influencing the suitability of the linear remnants appear to be the high level of network connectivity, the location on soils of high nutrient status, the high density of large trees and an acacia understorey. In highly fragmented landscapes, linear habitats as part of the remaining woodland mosaic have the potential to be an integral component in the conservation of woodland-dependent fauna. The habitat value of linear strips of vegetation should not be underestimated.

Lessons from large-scale conservation networks in Australia

Australia has seen a rapid growth in the establishment of networks of lands managed for connectivity conservation across tenures, at landscape and sub-continental scales. Such networks go under a variety of names, including biosphere reserves, biolinks, wildlife corridors and conservation management networks. Their establishment has varied from state government-led initiatives to those initiated by non-government organizations and interested landholders. We surveyed existing major landscape scale conservation initiatives for successes, failures and future directions and synthesized common themes. These themes included scale, importance of social and economic networks, leadership, governance, funding, conservation planning, the role of protected areas and communication. We discuss the emergence of national policy relating to National Wildlife Corridors in Australia and the relationship of this policy to the long standing commitment to build a comprehensive, adequate and representative National Reserve System. Finally we outline areas for further research for connectivity conservation projects in Australia.

Powerline corridors: degraded ecosystems or wildlife havens?

Management of powerline corridors in Australia has traditionally focused on the complete removal of vegetation using short rotation times owing to the perceived hazard of fire associated with corridor vegetation. Because of the intense management associated with fire hazards, little thought has been given to use of powerline corridors by wildlife. This has resulted in corridors traditionally being viewed as a source of fragmentation and habitat loss within forested ecosystems. We investigated the responses of small mammal communities living in a powerline corridor to management-induced vegetation changes at different successional stages, to determine whether a compromise could be reached between managing corridors for fire and biodiversity. Habitat modelling in the corridor and adjacent forest for three native and one introduced small mammal species demonstrated that species responded to changes in vegetation structural complexity, rather than time-since-management per se. Early seral stages of vegetation recovery after corridor management encouraged the introduced house mouse (Mus domesticus) into corridors and contributed little to biodiversity. Mid-seral-stage vegetation, however, provided habitat for native species that were rare in adjacent forest habitats. As the structural complexity of the vegetation increased, the small mammal community became similar to that of the forest so that corridor vegetation contributed fewer biodiversity benefits while posing an unacceptable fire risk. If ecologically sensitive management regimes are implemented to encourage mid-seral vegetation and avoid complete vegetation removal, powerline corridors have the potential to improve biodiversity. This would maintain landscape connectivity and provide habitat for native species uncommon in the forest while still limiting fuel loads in the corridor.

Public and stakeholder values of wildlife in Victoria, Australia

This paper explores the management implications of a recent study that was designed to explore public and stakeholder values of wildlife in Victoria, Australia. Questionnaires (n = 1431) were used to examine values and knowledge of wildlife held by residents from seven Victorian municipalities and members of six wildlife management stakeholder groups. The results suggest that most Victorians have a relatively strong emotional attachment to individual animals (the humanistic value) and are interested in learning about wildlife and the natural environment (the curiosity/learning/interacting value). In comparison, the negativistic, aesthetic, utilitarian-habitat and dominionistic/wildlife-consumption values were not expressed as strongly. These findings suggest that wildlife managers should expect support for wildlife management objectives that reflect the relatively strong humanistic orientation of Victorians and tailor management and education programs to appeal to this value and Victorians' interest in learning about wildlife.

Wildlife management in Australasia : perceptions of objectives and priorities

The aim of this study was to examine the values and attitudes held by Australasian wildlife managers as they relate to wildlife management issues, and to gain some insight into possible future directions and priorities for Australasian wildlife management. During December 2002 – February 2003, 138 questionnaires were completed by members of the Australasian Wildlife Management Society (AWMS) and registrants of the 2002 AWMS annual conference. Threatened species management, threatened communities/habitats, and management of introduced species were the issues rated as needing the highest priority for the Australasian Wildlife Management Society. Issues such as animal rights, genetically modified organisms and timber harvesting on public lands were the lowest-rating issues. Respondents expressed a strong belief in managing and controlling wildlife to achieve wildlife management objectives, a strong belief that wildlife should be protected and that wildlife managers should minimise the pain and suffering of individual animals, and a belief that resources should be directed towards conserving wildlife populations rather than protecting individual animals from non-threatened populations. While respondents held a strong belief that it is important to consult the community when developing wildlife management policies and programs, there was little support for a comanagerial approach where the community has a significant role to play in decision-making processes.

Gender differences in the perceptions of wildlife management objectives and priorities in Australasia

It is now well established that men and women often differ significantly in their attitudes and responses to workplace situations, challenges and policies. The aim of this study was to examine the effect of gender on perceptions and priorities held by Australasian wildlife managers. Data were collected via a questionnaire distributed during December 2002 – February 2003 to members of the Australasian Wildlife Management Society (AWMS) and registrants of the 2002 AWMS annual conference. The results show that there are now significantly more female AWMS members than there were in the early 1990s, a possible indication of a change in the wider wildlife management profession in Australasia. Consistent with previous research, male respondents held different views from female respondents about wildlife and wildlife management. In particular, male respondents were significantly more likely to express the ‘management/consumptive use of wildlife’ perspective than female respondents. Interestingly, this gap was observed only in the 18–30-year age category. The paper examines what these differences might mean for the future of wildlife management in Australasia.

Toward incorporating human dimensions information into wildlife management decision-making

This paper presents a comparison of values of wildlife held by stakeholder groups and public samples in Victoria, Australia, with a sample of wildlife managers' beliefs about these groups. It also examines the managers' views of the importance of utilizing human dimensions information in their decision-making. In-depth interviews were conducted with wildlife/environmental managers in a sample of state and local government agencies and members of wildlife management stakeholder groups. Questionnaires were used to explore values of wildlife held by stakeholder group members and the Victorian public. There are several instances of interviewed managers misunderstanding the values held by stakeholder groups and subsets of the Victorian public. Such discrepancies can be reduced by incorporating systematically obtained human dimensions information into management decisions. Interviewed wildlife managers appear to appreciate the importance of human dimensions information; however, there was some uncertainty about how it could be applied.

Wildlife management in Australasia : perceptions of objectives and priorities

The aim of this study was to examine the values and attitudes held by Australasian wildlife managers as they relate to wildlife management issues, and to gain some insight into possible future directions and priorities for Australasian wildlife management. During December 2002 – February 2003, 138 questionnaires were completed by members of the Australasian Wildlife Management Society (AWMS) and registrants of the 2002 AWMS annual conference. Threatened species management, threatened communities/habitats, and management of introduced species were the issues rated as needing the highest priority for the Australasian Wildlife Management Society. Issues such as animal rights, genetically modified organisms and timber harvesting on public lands were the lowest-rating issues. Respondents expressed a strong belief in managing and controlling wildlife to achieve wildlife management objectives, a strong belief that wildlife should be protected and that wildlife managers should minimise the pain and suffering of individual animals, and a belief that resources should be directed towards conserving wildlife populations rather than protecting individual animals from non-threatened populations. While respondents held a strong belief that it is important to consult the community when developing wildlife management policies and programs, there was little support for a comanagerial approach where the community has a significant role to play in decision-making processes.