Feast to famine: Sympatric predators respond differently to seasonal prey scarcity on the low-Arctic tundra

Resource fluctuation is a major driver of animal movement, influencing strategic choices such as residency vs nomadism, or social dynamics. The Arctic tundra is characterized by strong seasonality: resources are abundant during the short summers but scarce in winters. Therefore, expansion of boreal-forest species onto the tundra raises questions on how they cope with winter-resource scarcity. We examined a recent incursion by red foxes (Vulpes vulpes) onto the coastal tundra of northern Manitoba, an area historically occupied by Arctic foxes (Vulpes lagopus) that lacks access to anthropogenic foods, and compared seasonal shifts in space use of the two species. We used 4 years of telemetry data following 8 red foxes and 11 Arctic foxes to test the hypothesis that the movement tactics of both species are primarily driven by temporal variability of resources. We also predicted that the harsh tundra conditions in winter would drive red foxes to disperse more often and maintain larger home r..., Capture and satellite telemetry. – Between 2017 and 2019, we captured 10 red foxes and 13 Arctic foxes using Tomahawk (Model 208, Tomahawk Live Trap Co., WI) and padded leghold traps (Softcatch # 1.5, Oneida Victor Ltd, USA). Traps were placed on active dens or by protruding features (e.g., driftwood or spruce islets) and remained open continuously for up to one week. We checked the traps every 4–6 hours and closed them during extreme weather conditions (e.g., blizzard or temperatures below -25°C). We captured adult foxes from March to May when snow still covered the ground and facilitated travel over large distances, except for two adult foxes caught near our field camps in June 2018. We did not anesthetize the foxes, which were easily handled without chemical restraint. Foxes were first wrapped in a blanket and released from the traps, then we assessed sex and body condition, deployed an Iridium satellite collar (#4170 or 4270, Telonics, Mesa, Arizona, USA; ~100g, i.e., 2–4% of a fox ...,资源波动是驱动动物运动的核心驱动因子，可影响定居与游牧等生存策略选择，同时对种群社会动态产生调控作用。北极苔原具有极强的季节周期性：短暂夏季时资源丰沛，而冬季则资源极度匮乏。因此，北方森林物种向苔原的扩张引发了关键科学问题：这些物种如何应对冬季的资源短缺困境。本研究聚焦于红狐（Vulpes vulpes）近期对加拿大曼尼托巴省北部沿海苔原的侵入现象——该区域历史上仅由北极狐（Vulpes lagopus）栖息，且无法获取人为来源食物，并对比了两种狐狸的空间利用季节变化模式。我们依托追踪8只红狐与11只北极狐的4年遥测数据，验证了“两种狐狸的运动策略主要受资源的时间变异性驱动”这一研究假说。同时我们还预测，苔原冬季的严酷环境会促使红狐更频繁地扩散，并维持更大的家域…… 【捕获与卫星遥测方法】 2017年至2019年间，我们使用汤姆霍克（Tomahawk，型号208，美国威斯康星州Tomahawk Live Trap Co.）与软垫式夹腿陷阱（Softcatch #1.5，美国Oneida Victor Ltd）捕获了10只红狐与13只北极狐。陷阱被布设至活跃的狐穴周边或突出地标（如浮木、云杉小岛）处，并可持续开放长达一周。我们每4至6小时检查一次陷阱，且在极端天气（如暴风雪、气温低于-25℃）时关闭陷阱。我们于3月至5月间捕获成年狐狸——此时地面仍被积雪覆盖，便于长距离移动，仅2只成年狐狸于2018年6月在野外营地附近捕获。我们未对狐狸实施麻醉，所有个体均可在无需化学约束的情况下安全处置：首先用毛毯包裹狐狸并将其从陷阱中放出，随后评估其性别与身体状况，并安装了铱星（Iridium）卫星项圈（型号#4170或4270，美国亚利桑那州梅萨市Telonics公司，重量约100g，约占狐狸体重的2%至4%……