Predation risk drives long-term shifts in migratory behavior and demography in a large herbivore population

Migration is an adaptive life-history strategy that helps individuals across taxa maximize fitness by obtaining forage and avoiding predation risk. The mechanisms driving migratory changes are poorly understood, and links between migratory behavior, space use, and demographic consequences are rare. Here, we use a nearly 20-year record of individual-based monitoring of elk (Cervus canadensis) to test hypotheses for changing patterns of migration in a large herbivore, elk (Cervus canadensis), in and adjacent to a large protected area in Banff National Park (BNP), Canada. We test whether bottom-up (forage quality) or top-down (predation risk) factors explained trends in i) the proportion of individuals using 5 different migratory tactics, ii) differences in survival rates of migratory tactics during migration and whilst on summer ranges, iii) cause-specific mortality by wolves and grizzly bears, and iv) population abundance. We found dramatic shifts in migration consistent with behavioral ...

迁徙是一种适应性生活史策略，可帮助不同类群的生物个体通过获取食物资源、规避捕食风险来最大化自身适合度。目前学界对驱动迁徙行为变化的机制尚缺乏深入认知，且迁徙行为、空间利用与种群统计特征之间的关联研究亦较为稀缺。本研究依托加拿大班夫国家公园（Banff National Park, BNP）及其周边大型保护区域内近20年的加拿大马鹿（Cervus canadensis）个体监测记录，针对这种大型植食性动物的迁徙模式变化验证相关假说。我们将验证上行效应（bottom-up，即食物质量）与下行效应（top-down，即捕食风险）这两类因子能否解释下述趋势：① 采用5种不同迁徙策略的个体占比变化；② 不同迁徙策略个体在迁徙过程中及夏季活动区的存活率差异；③ 由灰狼与灰熊导致的特定死因死亡率；④ 种群丰度变化。本研究发现迁徙行为发生了显著变化，该变化与行为学……（原文未完整展示）