Dataset of how animal movement paths in a landscape vary due to wildfire

AbstractAnimals navigate landscapes based on perceived risks vs. rewards, as inferred from features of the landscape. In the wild, knowing how strongly animal movement is directed by landscape features is difficult to ascertain, but widespread disturbances such as wildfires can serve as natural experiments. We tested the hypothesis that wildfires homogenize the risk/reward landscape, causing movement to become less directed, given that fires reduce landscape complexity as habitat structures (e.g., tree cover, dense brush) are burned. We used satellite imagery of a research reserve in Northern California to count and categorize paths made primarily by mule deer (Odocoileus hemionus) in grasslands. Specifically, we compared pre-wildfire (August 2014) and post-wildfire (September 2018) image history layers among locations that were or were not impacted by wildfire (i.e., a Before/After Control/Impact design). Wildfire significantly altered spatial patterns of deer movement: more new paths were gained and more old paths were lost in areas of the reserve that were impacted by wildfire; movement patterns became less directed in response to fire, suggesting that the risk/reward landscape became more homogenous, as hypothesized. We found evidence to suggest that wildfire affects deer populations at spatial scales beyond their scale of direct impact and raises the interesting possibility that deer perceive risks and rewards at different spatial scales. In conclusion, our study provides an example of how animals integrate spatial information from the environment to make movement decisions, setting the stage for future work on the broader ecological implications for populations, communities, and ecosystems, an emerging interest in ecology.
MethodsAnimal paths were traced from satellite imagery before and after a wildfire, in areas impacted by fire and in unimpacted areas (i.e., a BACI design). Paths were then counted, categorized by size, and assessed to see whether paths were persistent or were formed or lost dynamically over time. This was a pandemic project.

摘要：动物会基于对景观特征的推断，权衡感知到的风险与收益，以此导航穿越各类景观。在野外环境中，明确景观特征对动物移动的引导强度极具挑战，但野火等大范围扰动可作为天然实验载体。我们提出研究假设：野火会烧毁树木覆盖、茂密灌丛等栖息地结构，降低景观复杂度，进而同质化风险与收益景观，导致动物移动的方向性减弱。我们利用北加州某研究保护区的卫星影像，对草原区域内以骡鹿（Odocoileus hemionus）为主形成的移动路径进行计数与分类。具体而言，我们采用前后对照影响（Before/After Control/Impact, BACI）设计，对比了受野火影响与未受影响区域在野火前（2014年8月）与野火后（2018年9月）的影像历史图层。结果显示，野火显著改变了鹿群移动的空间格局：受野火影响的保护区区域内，新增路径数量更多，原有路径消失比例更高；鹿群移动的方向性随野火发生显著减弱，印证了野火会使风险-收益景观趋于同质化的假设。本研究发现，野火对鹿群种群的影响范围超出其直接受影响的空间尺度，同时提示鹿群对风险与收益的感知可能存在不同的空间尺度，这一发现颇具研究价值。综上，本研究展示了动物如何整合环境空间信息以做出移动决策，为后续开展种群、群落与生态系统层面的广泛生态影响研究奠定了基础，这亦是当前生态学领域的新兴研究方向。

方法：我们基于野火发生前后的卫星影像，分别在受野火影响区域与未受影响区域（即前后对照影响（Before/After Control/Impact, BACI）设计）追踪动物移动路径。随后对路径进行计数、按规模分类，并评估路径是否持续存在，或是随时间动态形成或消失。本研究为新冠疫情期间开展的项目。