School of Environmental and Forest Sciences, University of Washington, Seattle, Washington, USA.
Washington Department of Fish and Wildlife, Spokane Valley, Washington, USA.
Ecol Appl. 2024 Jul;34(5):e3003. doi: 10.1002/eap.3003. Epub 2024 Jun 18.
Large terrestrial mammals increasingly rely on human-modified landscapes as anthropogenic footprints expand. Land management activities such as timber harvest, agriculture, and roads can influence prey population dynamics by altering forage resources and predation risk via changes in habitat, but these effects are not well understood in regions with diverse and changing predator guilds. In northeastern Washington state, USA, white-tailed deer (Odocoileus virginianus) are vulnerable to multiple carnivores, including recently returned gray wolves (Canis lupus), within a highly human-modified landscape. To understand the factors governing predator-prey dynamics in a human context, we radio-collared 280 white-tailed deer, 33 bobcats (Lynx rufus), 50 cougars (Puma concolor), 28 coyotes (C. latrans), and 14 wolves between 2016 and 2021. We first estimated deer vital rates and used a stage-structured matrix model to estimate their population growth rate. During the study, we observed a stable to declining deer population (lambda = 0.97, 95% confidence interval: 0.88, 1.05), with 74% of Monte Carlo simulations indicating population decrease and 26% of simulations indicating population increase. We then fit Cox proportional hazard models to evaluate how predator exposure, use of human-modified landscapes, and winter severity influenced deer survival and used these relationships to evaluate impacts on overall population growth. We found that the population growth rate was dually influenced by a negative direct effect of apex predators and a positive effect of timber harvest and agricultural areas. Cougars had a stronger effect on deer population dynamics than wolves, and mesopredators had little influence on the deer population growth rate. Areas of recent timber harvest had 55% more forage biomass than older forests, but horizontal visibility did not differ, suggesting that timber harvest did not influence predation risk. Although proximity to roads did not affect the overall population growth rate, vehicle collisions caused a substantial proportion of deer mortalities, and reducing these collisions could be a win-win for deer and humans. The influence of apex predators and forage indicates a dual limitation by top-down and bottom-up factors in this highly human-modified system, suggesting that a reduction in apex predators would intensify density-dependent regulation of the deer population owing to limited forage availability.
大型陆生哺乳动物越来越依赖于人类改造的景观，因为人类足迹在不断扩大。土地管理活动，如采伐木材、农业和道路，通过改变栖息地，可以影响猎物的种群动态，从而改变饲料资源和捕食风险，但在拥有多样化和不断变化的捕食者群体的地区，这些影响还不太清楚。在美国华盛顿州东北部，白尾鹿（Odocoileus virginianus）易受多种食肉动物的影响，包括最近返回的灰狼（Canis lupus），这些食肉动物生活在高度受人类改造的景观中。为了了解人类环境中捕食者-猎物动态的控制因素，我们在 2016 年至 2021 年间，为 280 只白尾鹿、33 只短尾猫（Lynx rufus）、50 只美洲狮（Puma concolor）、28 只郊狼（C. latrans）和 14 只狼佩戴无线电项圈。我们首先估计了鹿的生命参数，并使用了一个阶段结构矩阵模型来估计它们的种群增长率。在研究过程中，我们观察到鹿群数量稳定到减少（lambda=0.97，95%置信区间：0.88，1.05），74%的蒙特卡罗模拟表明种群减少，26%的模拟表明种群增加。然后，我们拟合了 Cox 比例风险模型，以评估捕食者暴露、使用人类改造的景观和冬季严重程度如何影响鹿的存活率，并利用这些关系来评估对总体种群增长的影响。我们发现，种群增长率受到顶级捕食者的直接负效应和木材采伐以及农业区的正效应的双重影响。美洲狮对鹿种群动态的影响大于狼，而中型捕食者对鹿种群增长率的影响较小。最近进行木材采伐的区域的饲料生物量比老林多出 55%，但水平可见度没有差异，这表明木材采伐并没有影响捕食风险。尽管与道路的接近程度没有影响总体人口增长率，但车辆碰撞导致了相当比例的鹿死亡，减少这些碰撞对鹿和人类来说都可能是双赢的。顶级捕食者和饲料的影响表明，在这个高度受人类改造的系统中，存在自上而下和自下而上因素的双重限制，这表明由于饲料供应有限，顶级捕食者的减少将加剧鹿种群对密度的依赖调节。
