Flower Charles E, Dalton Jennifer E, Whelan Christopher J, Brown Joel S, Gonzalez-Meler Miquel A
Department of Biological Sciences, University of Illinois at Chicago, 845 West Taylor Street, Chicago, IL, 60607, USA.
USDA Forest Service, Northern Research Station, 359 Main Rd, Delaware, OH, 43015, USA.
Oecologia. 2019 May;190(1):243-254. doi: 10.1007/s00442-019-04400-5. Epub 2019 Apr 23.
We investigated the roles of vegetation structure, micro-topographic relief, and predator activity patterns (time of day) on the perception of predatory risk of arctic ground squirrels (Urocitellus parryii), an abundant pan-Arctic omnivore, in Arctic Circle tundra on the North Slope of Alaska, where tundra vegetation structure has been predicted to change in response to climate. We quantified foraging intensity by measuring the giving-up densities (GUDs) of the arctic ground squirrels in experimental foraging patches along a heath-graminoid-shrub moist tundra gradient. We hypothesized that foraging intensity of arctic ground squirrels would be greatest and GUDs lowest, where low-stature vegetation or raised micro-topography improves sightlines for predator detection. Furthermore, GUDs should vary with time of day and reflect 24-h cycles of varying predation risk. Foraging intensity varied temporally, being highest in the afternoon and lowest overnight. During the morning, foraging intensity was inversely correlated with the normalized difference vegetation index (NDVI), a proxy for vegetation productivity and cover. Foraging was additionally measured within landscapes of fear, confirming that vegetative and topographic obstructions of sightlines reduces foraging intensity and increases GUDs. We conclude that arctic ground squirrels may affect Arctic Circle vegetation of tundra ecosystems, but these effects will vary spatially and temporally.
我们研究了植被结构、微地形起伏和捕食者活动模式（一天中的时间）对北极地松鼠（Urocitellus parryii，一种分布广泛的泛北极杂食动物）在阿拉斯加北坡北极圈冻原上对捕食风险感知的作用，在该地区，冻原植被结构预计会因气候而发生变化。我们通过测量北极地松鼠在沿着石南 - 禾本科植物 - 灌木湿润冻原梯度的实验觅食斑块中的放弃密度（GUDs）来量化觅食强度。我们假设，在低矮植被或微地形较高从而改善捕食者检测视线的地方，北极地松鼠的觅食强度会最大，而GUDs会最低。此外，GUDs应随一天中的时间变化，并反映出不同捕食风险的24小时周期。觅食强度随时间变化，下午最高，夜间最低。在早晨，觅食强度与归一化植被指数（NDVI，植被生产力和覆盖度的一个指标）呈负相关。我们还在恐惧景观中测量了觅食情况，证实了视线的植被和地形阻碍会降低觅食强度并增加GUDs。我们得出结论，北极地松鼠可能会影响北极圈冻原生态系统的植被，但这些影响会在空间和时间上有所不同。
