Centre for Ecosystem Science, University of New South Wales, Sydney, NSW, 2052, Australia.
Arid Recovery, P.O. Box 147, Roxby Downs, SA, 5725, Australia.
Conserv Biol. 2020 Feb;34(1):220-231. doi: 10.1111/cobi.13389. Epub 2019 Aug 1.
Spillover effects are an expansion of conservation benefits beyond protected areas through dispersal of species that reside within. They have been well documented in marine but not terrestrial systems. To understand the effects on wildlife created by conservation fences, we explored the internal and external gradients of activity in mammal, reptile, and bird species at a conservation reserve in arid Australia that is fenced to exclude invasive rabbits (Oryctolagus cuniculus), cats (Felis catus), and foxes (Vulpes vulpes). Two methods were used: counts of animal tracks along transects on sand dunes and captures at pitfall-trapping sites. In both cases, sites were spaced at different distances from the reserve fenceline inside and outside the reserve. We recorded a range of spillover, source-sink, step, and barrier effects that combined to create a zone within and around the reserve with fence-induced species-specific wildlife gradients. Two endemic rodents but none of the 4 mammal species reintroduced to the reserve showed positive spillover effects. Barrier effects, where activity was highest close to the fence, were recorded for the feral cat and native bettong (Bettongia lesueur), species that could not breach the fence. In comparison, some reptiles and native mammal species that could permeate the fence displayed source-sink effects; that is, their activity levels were reduced close to the fence likely due to constant emigration to the side with lower density. Activity of some reptiles was lowest at sites inside the reserve and gradually increased at outside sites with distance from the fence, a gradient likely related to trophic cascades triggered by predator exclusion. Our result shows that fenced reserves can create overlapping layers of species-specific gradients related to each species' ability to permeate the fence and its varying susceptibility to threats. Managers should be aware that these gradients may extend for several kilometers either side of the fence and that not all contained species will increase in abundance. Creating wider conservation benefits may require increased fence permeability and threat reduction outside the fence.
溢出效应是指通过保护区域内物种的扩散，将保护效益扩大到保护区以外的区域。这些效应在海洋生态系统中得到了充分的证明，但在陆地生态系统中却没有。为了了解保护围栏对野生动物的影响，我们在澳大利亚干旱地区的一个保护储备区内探索了哺乳动物、爬行动物和鸟类物种的内部和外部活动梯度，该储备区用围栏围住以排除入侵的兔子（Oryctolagus cuniculus）、猫（Felis catus）和狐狸（Vulpes vulpes）。我们使用了两种方法：在沙丘的横截线上计算动物足迹的数量和在陷阱陷阱点进行捕捉。在这两种情况下，站点都以不同的距离从保护区围栏内和围栏外的保护区内部和外部进行间隔。我们记录了一系列溢出、源汇、步长和障碍效应，这些效应结合在一起，在保护区内和周围形成了一个具有围栏诱导的特定物种野生动物梯度的区域。两种特有啮齿动物，但没有一种重新引入保护区的 4 种哺乳动物表现出积极的溢出效应。在无法突破围栏的情况下，记录到了围栏附近活动最高的围栏效应，例如，对于野生猫和本地 Bettongia lesueur（ Bettongia lesueur ）。相比之下，一些能够穿透围栏的爬行动物和本地哺乳动物表现出源汇效应；也就是说，它们的活动水平在靠近围栏的地方降低，这可能是由于不断向密度较低的一侧移民所致。一些爬行动物的活动在保护区内的地点最低，随着与围栏的距离增加而逐渐增加，这种梯度可能与由于捕食者排除而引发的营养级联有关。我们的结果表明，围栏保护区可以创建与每个物种穿透围栏的能力及其对威胁的不同易感性相关的重叠的特定物种梯度层。管理者应该意识到，这些梯度可能会在围栏的两侧延伸数公里，并且并非所有包含的物种都会增加数量。要创造更广泛的保护效益，可能需要增加围栏的渗透性并减少围栏外的威胁。
