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，从在温暖气候下迁徙3000英里过冬的帝王蝶到每年在北极和南极之间飞行的北极燕鸥。由于人类干扰、栖息地丧失和气候变化，世界范围内的迁徙物种正在减少。在这些持续变化的存在下，移民生态已成为一个重要的管理问题。这项研究延续了一项为期15年的麋鹿研究，以了解为什么在不同的迁徙物种中，单个种群中有迁徙的个体，也有不迁徙的个体。该项目将有助于了解麋鹿迁徙决策的原因，以及改变迁徙行为对麋鹿保护和管理的影响。研究人员将招募新闻专业的研究生，他们将开发多样化的媒体渠道来广泛传播研究结果，而地理专业的研究生将开发网络界面，让公众可以虚拟地观察麋鹿的迁徙。该项目将通过蒙大拿大学的印第安人自然资源项目为印第安人学生提供实习机会。对迁徙动物的普遍迷恋，以及麋鹿对自然资源保护主义者、猎人和印第安人的广泛吸引力，都保证了有效的公民宣传和参与。研究人员将使用部分迁移的麋鹿种群作为模型系统，以了解部分迁移的环境依赖成本和收益。该项目建立在对已知年龄的300多只单独标记的雌性麋鹿的人口统计、个体繁殖率和幼崽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生殖史等内在因素和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，以理解为什么长寿哺乳动物在面对环境变化时在迁移策略之间切换。接下来，他们将把转换原因的结果纳入一个人口模型，该模型将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检验部分迁移的种群动态效应以及自下而上（觅食）与自上而下（捕食）力量对种群增长率的相对重要性的两种替代假设。

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.