The importance of thermal resources to terrestrial ectotherms has been well documented but less often considered in larger-scale analyses of habitat use and selection, such as those routinely conducted using standard habitat features such as vegetation and physical structure. Selection of habitat based on thermal attributes may be of particular importance for ectothermic species, especially in colder climates. In Canada, Western Rattlesnakes (Crotalus oreganus) reach their northern limits, with limited time to conduct annual migratory movements between hibernacula and summer habitat. We radio-tracked 35 male snakes departing from 10 different hibernacula. We examined coarse-scale differences in migratory movements across the region, and then compared the route of each snake with thermal landscapes and ruggedness GIS maps generated for different periods of the animals’ active season. We observed dichotomous habitat use (grasslands versus upland forests) throughout most of the species’ northern range, reflected in different migratory movements of male snakes emanating from different hibernacula. Snakes utilizing higher-elevation forests moved further during the course of their annual migrations, and these snakes were more likely to use warmer areas of the landscape. In addition to thermal benefits, advantages gained from selective migratory patterns may include prey availability and outbreeding. Testing these alternative hypotheses was beyond the scope of this study, and to collect the data to do so will require overcoming certain challenges. Still, insight into migratory differences between rattlesnake populations and the causal mechanism(s) of migrations will improve our ability to assess the implications of landscape change, management, and efficacy of conservation planning. Our findings suggest that such assessments may need to be tailored to individual dens and the migration strategies of their inhabitants. Additionally, local and landscape-scale migration patterns, as detected in this study, will have repercussions for snakes under climate-induced shifts in ecosystem boundaries and thermal regimes.

中文翻译：

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响尾蛇迁徙和热景观的影响。

热资源对陆地变温动物的重要性已得到充分证明，但在栖息地使用和选择的大规模分析中很少考虑，例如那些常规使用标准栖息地特征（如植被和物理结构）进行的分析。基于热属性的栖息地选择对于变温物种可能特别重要，尤其是在较冷的气候中。在加拿大，西部响尾蛇 (Crotalus oreganus) 到达其北部极限，在冬眠和夏季栖息地之间进行年度迁徙活动的时间有限。我们对从 10 个不同冬眠区出发的 35 条雄性蛇进行了无线电跟踪。我们研究了该地区移民运动的粗略差异，然后将每条蛇的路线与动物活跃季节不同时期生成的热景观和崎岖 GIS 地图进行比较。我们在该物种的大部分北部范围内观察到二分栖息地使用（草原与高地森林），这反映在来自不同冬眠的雄性蛇的不同迁徙运动中。利用高海拔森林的蛇在其年度迁徙过程中移动得更远，这些蛇更有可能使用景观中较温暖的区域。除了热效益外，从选择性迁徙模式中获得的优势可能包括猎物可用性和近亲繁殖。测试这些替代假设超出了本研究的范围，为此收集数据需要克服某些挑战。仍然，深入了解响尾蛇种群之间的迁徙差异和迁徙的因果机制将提高我们评估景观变化、管理和保护规划有效性的影响的能力。我们的研究结果表明，此类评估可能需要针对个体巢穴及其居民的迁移策略进行调整。此外，本研究中检测到的局部和景观尺度迁移模式将对气候引起的生态系统边界和热状态变化下的蛇产生影响。我们的研究结果表明，此类评估可能需要针对个体巢穴及其居民的迁移策略进行调整。此外，本研究中检测到的局部和景观尺度迁移模式将对气候引起的生态系统边界和热状态变化下的蛇产生影响。我们的研究结果表明，此类评估可能需要针对个体巢穴及其居民的迁移策略进行调整。此外，本研究中检测到的局部和景观尺度迁移模式将对气候引起的生态系统边界和热状态变化下的蛇产生影响。