Replication Data for: Accounting for food web dynamics when assessing the impact of mesopredator control on declining prey populations

These are files to be able to reproduce the analyses and plots in Henden et al. 2020 in Journal of Applied Ecology. Data on willow ptarmigan are based on line transect distance sampling. Small rodent data are based on an abundance index from sampling using the small quadrat sampling scheme. Carcass data comes from a national database of dead reindeer found Harvest data comes from detailed records from the main management and landowner, FeFo, in Finnmark. Data on red foxes comes from an ongoing fox decimation program on Varanger Peninsula.
Abstract from accepted paper in Journal of Applied Ecology Increasing populations of mesopredators are suspected to cause declines in vulnerable wildlife to the extent that mesopredator decimation actions (culling) have become commonplace. Design constraints, especially a lack of spatial replication, often hamper the assessment of the impact of such actions. However, extensive temporal replication (i.e. time series) and accounting for potentially confounding variables may alleviate this problem. In alpine-arctic tundra, the red fox Vulpes vulpes is increasing, while many bird species are declining, likely due to increased predation. Here, we assessed the impact of a long-term (12-year) and spatially extensive (~3500km2) red fox culling action on the red listed willow ptarmigan Lagopus lagopus in the Norwegian Arctic. Ptarmigan populations were monitored annually in the impact area and in an adjacent no-action area, including a 5-year period before the action commenced. While logistical constraints prohibited monitoring of red fox population densities, the number of culled foxes and three influential food web covariates were monitored after the onset of the culling action. A Before-After-Control-Impact-Paired-Series (BACIPS) analysis without food web covariates indicated that red fox culling curbed the decline of the population in the impact area, and that ptarmigan population density became ~25 % higher than in the reference area. Spatially and temporally variable drivers within the food web confounded the simple BACIPS analysis. Accounting for three food web drivers as covariates in a linear mixed model after the onset of action, yielded a more unbiased impact estimate that amounted to ~40 % higher ptarmigan population density (4.3 more ptarmigan/km2) in the red fox impact area. Synthesis and applications. We provide the first evidence of the role of the recent expansion of red fox in the decline of bird populations in tundra. We also show that red fox culling may be able to curb such declines, given that management actions are large-scale and long-term. As mesopredator culling campaigns are often expensive and controversial, it is important that their impacts are accurately assessed. We demonstrate that the accuracy of impact assessments can be profoundly increased by monitoring drivers of food web dynamics that impinge on the target species so that such drivers can be included as covariates in the analysis. This applies in particular to declining bird populations in boreal and arctic food webs ruled by strong multi-annual interaction cycles.

本数据集旨在复现《应用生态学杂志》中Henden等人在2020年的分析及图表。其中关于柳雷鸟的数据基于线状样条距离抽样法收集。小型啮齿类动物的数据则基于小样方抽样方案所获得的丰度指数。尸体数据来源于全国范围内的死鹿数据库。收获数据则源自芬马克地区主要的管理者和土地所有者FeFo的详细记录。关于赤狐的数据则来自Varanger半岛的赤狐灭绝计划。摘要摘自《应用生态学杂志》已接受论文：中值捕食者数量的增加疑似导致了易受伤害野生动物数量的下降，以至于中值捕食者灭绝行动（捕杀）已变得司空见惯。设计限制，尤其是空间重复性的缺乏，通常阻碍了对这类行动影响的评估。然而，广泛的时序重复（即时间序列）以及考虑潜在的混杂变量可能有助于缓解这一问题。在高山-北极苔原中，赤狐（Vulpes vulpes）的数量正在增加，而许多鸟类物种的数量正在下降，这很可能是因为捕食压力的增加。在本研究中，我们评估了在挪威北极地区对赤狐进行长期（12年）且空间广泛（约3500平方公里）的捕杀行动对红色柳雷鸟（Lagopus lagopus）的影响。雷鸟种群在行动影响区域及其相邻的无行动区域进行了年度监测，包括行动开始前5年。由于后勤限制，无法监测赤狐种群密度，但在捕杀行动开始后，监测了捕杀的狐狸数量和三个影响食物网的关键协变量。在没有食物网协变量的情况下进行的“前-后-控制-影响-配对系列”（BACIPS）分析表明，赤狐捕杀行动抑制了影响区域雷鸟种群数量的下降，并且雷鸟种群密度比参考区域高出约25%。食物网中的空间和时间变化的驱动因素混淆了简单的BACIPS分析。在行动开始后，将三个食物网驱动因素作为协变量纳入线性混合模型，得到了一个更加公正的影响估计，即在赤狐影响区域内雷鸟种群密度提高了约40%（每平方公里增加4.3只雷鸟）。综合与应用。我们提供了关于赤狐近期扩张导致苔原鸟类数量下降的第一手证据。我们还表明，如果管理行动是大规模且长期的，赤狐捕杀可能能够抑制这种下降。由于中值捕食者捕杀行动通常成本高昂且颇具争议，因此准确评估其影响至关重要。我们证明，通过监测影响目标物种的食物网动态驱动因素，可以在分析中将这些驱动因素作为协变量，从而显著提高影响评估的准确性。这尤其适用于受强大多年交互周期统治的北方和北极食物网中正在下降的鸟类种群。