Data from: A test of the green wave hypothesis in omnivorous brown bears across North America

<b>Abstract</b><br/><p>Herbivorous animals tend to seek out plants at intermediate phenological states to improve energy intake while minimizing consumption of fibrous material. In some ecosystems, the timing of green-up is heterogeneous and propagates across space in a wave-like pattern, known as the green wave. Tracking the green wave allows individuals to prolong access to higher-quality forage. While there is a plethora of empirical support for such behavior in herbivorous taxa, the green wave hypothesis (GWH) is nuanced based on factors such as body morphometrics and digestive capacity. Furthermore, little is known about whether other taxa, such as omnivores, track the green wave. Our objective was to assess whether the GWH can be extended to explain the movements of omnivores. Using GPS collar data from seven populations (n = 127 individuals) of brown bears (<em>Ursus</em> <em>arctos</em>) across their entire North American range, we first tested whether bears tracked the green wave. Using conditional resource selection functions, we found that variation in proxies of vegetative forage quality better-explained movement and habitat selection than proxies of forage biomass in over half of the bears in our study, providing evidence of green wave tracking. Second, we assess factors that explained variation in green wave tracking using linear mixed-effects models. Green wave tracking in brown bears was explained by the variation in availability of green-up within spring home ranges, and how green-up transitioned across those home ranges. Our results demonstrate that the GWH can partially explain movement of a non-migratory omnivorous species, extending the generality of the GWH as a broad predictor of animal space use. The green wave is another resource wave brown bears track, and our findings help predict brown bear space use, which can be used to guide conservation and habitat restoration efforts.</p>

摘要<br/><p>草食动物往往会选择处于物候中期的植物，以在提升能量摄入的同时减少纤维物质的摄取。在部分生态系统中，植被返青的时间分布具有异质性，并以波状模式在空间中扩散，该现象被称为绿浪（green wave）。追踪绿浪能够让动物延长获取高质量草料的时段。尽管已有大量实证研究支持草食类群的这类行为，但绿浪假说（green wave hypothesis, GWH）会因身体形态特征、消化能力等因素而呈现出复杂差异。此外，对于杂食类等其他类群是否会追踪绿浪，目前尚缺乏足够的研究。本研究旨在评估绿浪假说能否用于解释杂食动物的移动行为。我们使用了分布于北美全境的7个棕熊（*Ursus arctos*）种群（共127头个体）的GPS项圈数据，首先检验了棕熊是否会追踪绿浪：采用条件资源选择函数（conditional resource selection functions）分析发现，在超过半数的研究个体中，植被草料质量的替代指标对移动与栖息地选择的解释力优于草料生物量的替代指标，这为棕熊追踪绿浪提供了实证证据。其次，我们通过线性混合效应模型（linear mixed-effects models）分析了绿浪追踪行为的变异影响因素。结果显示，棕熊的绿浪追踪行为可通过春季家域内返青资源的可获得性，以及返青过程在该家域内的扩散特征进行解释。本研究证实，绿浪假说可部分解释非迁徙杂食物种的移动模式，拓展了绿浪假说作为动物空间利用通用预测因子的普适性。绿浪是棕熊追踪的又一类资源波动，本研究结果有助于预测棕熊的空间利用模式，可用于指导相关保护与栖息地修复工作。</p>