LTREB: TESTING FOR FACULTATIVE SWITCHING BETWEEN MIGRATORY STRATEGIES IN A PARTIALLY MIGRATORY, LONG-LIVED LARGE HERBIVORE POPULATION

动物迁徙是最壮观的自然现象之一，从迁徙长达 3,000 英里以在温暖气候中越冬的帝王蝶，到每年在北极和南极之间迁徙的北极燕鸥。由于人类干扰、栖息地丧失和气候变化，全球迁徙物种正在减少。在这些持续变化的情况下，移民生态已成为一个重要的管理问题。这项研究扩展了对麋鹿长达 15 年的研究，以了解为什么在不同的迁徙物种中，同一种群中存在会迁徙的个体和不迁徙的个体。该项目将有助于了解麋鹿迁徙决策的原因以及迁徙行为改变对麋鹿保护和管理的影响。研究人员将让新闻专业的研究生参与进来，他们将开发多种媒体渠道来广泛传播结果；研究人员将吸引地理专业的研究生开发网络界面，让公众以虚拟方式观看麋鹿的迁徙。该项目将通过蒙大拿大学的美国原住民自然资源项目为美国原住民学生提供实习机会。人们对迁徙动物的普遍迷恋，加上麋鹿对自然资源保护主义者、猎人和美洲原住民的广泛吸引力，保证了有效的公民宣传和参与。研究人员将使用部分迁徙的麋鹿种群作为模型系统，以了解部分迁徙的环境相关成本和收益。 该项目建立在对 300 多只已知年龄、单独标记的雌性麋鹿的人口统计、个体繁殖率和幼年存活率的长期了解基础上，并结合全球定位系统 (GPS) 项圈测量的迁徙行为的空间分析。研究人员将监测年龄和繁殖史等内在因素以及饲料和捕食风险等外在因素，以测试竞争和相互作用的假设，以了解为什么长寿的哺乳动物在面对环境变化时会在迁徙策略之间切换。接下来，他们将把关于转换原因的结果纳入人口模型，该模型明确测试转换对人口动态的影响。贝叶斯状态空间种群模型、贝叶斯模型选择以及具有和不具有不同切换函数的竞争模型的交叉验证将测试部分迁移对种群动态影响的两种替代假设，以及自下而上（觅食）与自上而下（捕食）力量对种群增长率的相对重要性。

Animal migrations figure among the most spectacular natural phenomena, ranging from Monarch butterflies that migrate up to 3,000 miles to over-winter in warm climates to Arctic terns that travel each year between the Arctic and the Antarctic. Migratory species are declining worldwide due to human disturbance, habitat loss, and climate change. In the presence of these ongoing changes, the ecology of migration has become an important management issue. This research extends a 15-year study of elk to understand why, across migratory species, there are individuals that migrate and those that do not migrate within a single population. The project will help understand the causes of migratory decision-making among elk and the implications of altered migratory behavior for elk conservation and management. The researchers will engage graduate students in journalism, who will develop diverse media outlets to communicate results broadly, and in geography, who will develop web interfaces for the public to view elk migration virtually. The project will offer internships to Native American students through the Native American Natural Resource Program at the University of Montana. General fascination with migratory animals along with the broad appeal of elk to conservationists, hunters, and Native Americans alike promise effective citizen outreach and engagement. The researchers will use a partly-migratory population of elk as a model system to understand the context-dependent costs and benefits of partial migration. The project builds on long-term knowledge of the demography of more than 300 individually marked female elk of known age, individual reproductive rates, and juvenile survival rates, combined with spatial analyses of migratory behavior measured by Global Positioning System (GPS) collars. The researchers will monitor both intrinsic factors such as age and reproductive history and extrinsic factors such as forage and predation risk to test competing and interacting hypotheses to understand why a long-lived mammal switches between migratory strategies in the face of environmental change. They will next incorporate results on the causes of switching into a population model that explicitly tests for the effects of switching on population dynamics. A Bayesian state-space population model, Bayesian model selection, and cross-validation of competing models with and without different switching functions will test between two alternate hypotheses for the population dynamic effects of partial migration as well as the relative importance of bottom-up (forage) versus top-down (predation) forces on population growth rates.