Temporal Patterns in the Abundance of a Critically Endangered Marsupial Relates to Disturbance by Roads and Agriculture

The aim of this study was to investigate how landscape disturbance associated with roads, agriculture and forestry influenced temporal patterns in woylie (Bettongia penicillata) abundance before, during and after periods of rapid population change. Data were collected from an area of approximately 140,000 ha of forest within the Upper Warren region in south-western Australia. Woylie abundance was measured using cage trapping at 22 grid and five transect locations with varying degrees of landscape disturbance between 1994 and 2012. We found evidence that the distribution and abundance of woylies over time appears to be related to the degree of fragmentation by roads and proximity to agriculture. Sites furthest from agriculture supported a greater abundance of woylies and had slower rates of population decline. Sites with fewer roads had a greater abundance of woylies generally and a greater rate of increase in abundance after the implementation of invasive predator control. The results of this study suggest that landscape disturbance is less important at peak population densities, but during times of environmental and population change, sites less dissected by roads and agriculture better support woylie populations. This may be due to the role these factors play in increasing the vulnerability of woylies to introduced predators, population fragmentation, weed species invasion, mortality from road collisions or a reduction in available habitat. Strategies that reduce the impact of disturbance on woylie populations could include the rationalisation of forest tracks and consolidation of contiguous habitat through the acquisition of private property. Reducing the impact of disturbance in the Upper Warren region could improve the resilience of this critically important woylie population during future environmental change.

本研究旨在探究与道路、农业及林业相关的景观干扰，在种群快速变化阶段的前、中、后期，如何影响沃利袋狸（woylie, Bettongia penicillata）的丰度时间动态模式。研究数据采集自澳大利亚西南部上沃伦地区的一片约14万公顷的森林区域。1994年至2012年间，研究人员通过笼捕法对22个样方网格与5条样带点位的沃利袋狸丰度进行调查，各点位的景观干扰程度存在差异。研究结果显示，沃利袋狸的分布与丰度随时间变化的模式，似乎与道路造成的生境破碎化程度以及距农业区的远近存在显著关联。距农业区越远的样地，沃利袋狸丰度越高，种群衰退速率也越缓慢。整体而言，道路密度更低的样地，沃利袋狸丰度更高；且在实施入侵捕食者防控措施后，这类样地的种群丰度增长速率也更快。本研究结果表明，景观干扰在种群密度峰值阶段的影响相对较弱，但在环境与种群发生动态变化的时期，受道路与农业活动切割程度更低的生境，更能有效支撑沃利袋狸种群存续。这一现象可能源于以下机制：上述干扰因素会提升沃利袋狸面对外来捕食者的脆弱性、加剧种群破碎化、促进杂草入侵、增加道路碰撞致死风险，或是缩减可利用栖息地面积。可用于降低干扰对沃利袋狸种群影响的保护策略包括：合理规划林道网络，以及通过收购私有土地整合连通生境斑块。在上沃伦地区降低景观干扰影响，可提升这一极度重要的沃利袋狸种群在未来环境变化中的恢复力。