Data_Sheet_1_Don't stop me now: Managed fence gaps could allow migratory ungulates to track dynamic resources and reduce fence related energy loss.pdf

In semi-arid environments characterized by erratic rainfall and scattered primary production, migratory movements are a key survival strategy of large herbivores to track resources over vast areas. Veterinary Cordon Fences (VCFs), intended to reduce wildlife-livestock disease transmission, fragment large parts of southern Africa and have limited the movements of large wild mammals for over 60 years. Consequently, wildlife-fence interactions are frequent and often result in perforations of the fence, mainly caused by elephants. Yet, we lack knowledge about at which times fences act as barriers, how fences directly alter the energy expenditure of native herbivores, and what the consequences of impermeability are. We studied 2-year ungulate movements in three common antelopes (springbok, kudu, eland) across a perforated part of Namibia's VCF separating a wildlife reserve and Etosha National Park using GPS telemetry, accelerometer measurements, and satellite imagery. We identified 2905 fence interaction events which we used to evaluate critical times of encounters and direct fence effects on energy expenditure. Using vegetation type-specific greenness dynamics, we quantified what animals gained in terms of high quality food resources from crossing the VCF. Our results show that the perforation of the VCF sustains herbivore-vegetation interactions in the savanna with its scattered resources. Fence permeability led to peaks in crossing numbers during the first flush of woody plants before the rain started. Kudu and eland often showed increased energy expenditure when crossing the fence. Energy expenditure was lowered during the frequent interactions of ungulates standing at the fence. We found no alteration of energy expenditure when springbok immediately found and crossed fence breaches. Our results indicate that constantly open gaps did not affect energy expenditure, while gaps with obstacles increased motion. Closing gaps may have confused ungulates and modified their intended movements. While browsing, sedentary kudu's use of space was less affected by the VCF; migratory, mixed-feeding springbok, and eland benefited from gaps by gaining forage quality and quantity after crossing. This highlights the importance of access to vast areas to allow ungulates to track vital vegetation patches.

在降雨不定、初级生产力分布零散的半干旱环境中，迁徙活动是大型植食动物在广袤区域追踪资源的关键生存策略。旨在减少野生动物与家畜疾病传播的防疫隔离围栏（Veterinary Cordon Fences, VCFs），将南非大片区域割裂开来，六十余年来持续限制了大型野生哺乳动物的活动范围。因此，野生动物与围栏的交互行为频发，且常导致围栏出现破损，此类破损多由大象造成。然而目前我们仍不清楚，围栏会在何时起到阻隔作用、如何直接改变本土植食动物的能量消耗，以及围栏的不渗透性会带来何种后果。本研究依托GPS遥测、加速度计测量与卫星影像技术，对纳米比亚一处分隔野生动物保护区与埃托沙国家公园的破损防疫隔离围栏周边的3种常见羚羊（跳羚、大捻角羚、大羚羊）的有蹄类动物移动行为开展了为期2年的观测。本研究共识别出2905次围栏交互事件，以此评估动物与围栏相遇的关键时段，以及围栏对动物能量消耗的直接影响。借助植被类型特异性的绿度动态数据，本研究量化了动物穿越防疫隔离围栏后所能获得的优质食物资源收益。研究结果显示，防疫隔离围栏的破损维持了资源零散分布的稀树草原内的植食动物-植被交互关系。在雨季来临前木本植物首次抽芽的时段，围栏的通透性会导致动物穿越围栏的频次达到峰值。大捻角羚与大羚羊在穿越围栏时，其能量消耗通常会升高；而当有蹄类动物在围栏处频繁停留交互时，能量消耗会有所降低。跳羚一旦发现围栏破损并即刻穿越时，其能量消耗并未出现变化。研究结果表明，持续开放的围栏缺口不会影响动物的能量消耗，但带有障碍物的缺口则会增加动物的运动能耗。封堵围栏缺口可能会扰乱有蹄类动物的行动，并改变它们原本的行进路线。作为植食性且活动范围相对固定的物种，大捻角羚的空间利用受防疫隔离围栏的影响较小；而具有迁徙习性的混合食性物种跳羚与大羚羊，则可通过围栏缺口获益——穿越围栏后它们能获得更高品质与更充足的草料。这凸显了为有蹄类动物提供广袤活动区域的重要性，使其能够追踪关键的植被斑块资源。