Natural regeneration on seismic lines influences movement behaviour of wolves and grizzly bears

Across the boreal forest of Canada, habitat disturbance is the ultimate cause of caribou (Rangifer tarandus caribou) declines. Habitat restoration is a focus of caribou recovery efforts, with a goal to finding ways to reduce predator use of disturbances, and caribou-predator encounters. One of the most pervasive disturbances within caribou ranges in Alberta, Canada are seismic lines cleared for energy exploration. Seismic lines facilitate predator movement, and although vegetation on some seismic lines is regenerating, it remains unknown whether vegetation regrowth is sufficient to alter predator response. We used Light Detection and Ranging (LiDAR) data, and GPS locations, to understand how vegetation and other attributes of seismic lines influence movements of two predators, wolves (Canis lupus) and grizzly bears (Ursus arctos). During winter, wolves moved towards seismic lines regardless of vegetation height, while during spring wolves moved towards seismic lines with higher vegetation. During summer, wolves moved towards seismic lines with lower vegetation and also moved faster near seismic lines with vegetation <0.7 m. Seismic lines with lower vegetation height were preferred by grizzly bears during spring and summer, but there was no relationship between vegetation height and grizzly bear movement rates. These results suggest that wolves use seismic lines for travel during summer, but during winter wolf movements relative to seismic lines could be influenced by factors additional to movement efficiency; potentially enhanced access to areas frequented by ungulate prey. Grizzly bears may be using seismic lines for movement, but could also be using seismic lines as a source of vegetative food or ungulate prey. To reduce wolf movement rate, restoration could focus on seismic lines with vegetation <1 m in height. However our results revealed that seismic lines continue to influence wolf movement behaviour decades after they were built, and even at later stages of regeneration. Therefore it remains unknown at what stage of natural regeneration, if any, wolves cease to respond to seismic lines. To reduce wolf response to seismic lines, active restoration tactics like blocking seismic lines and tree planting, along with management of alternate prey, could be evaluated.

在加拿大北方针叶林中，生境干扰是北美驯鹿（Rangifer tarandus caribou）种群数量下降的根本原因。生境修复是北美驯鹿种群恢复工作的核心方向，其目标为探索降低捕食者对干扰生境的利用、减少驯鹿与捕食者遭遇概率的可行路径。加拿大阿尔伯塔省境内北美驯鹿活动范围内，分布最广泛的干扰生境之一是为能源勘探修建的地震勘探线（seismic lines）。此类勘探线会便利捕食者的移动；尽管部分地震勘探线上的植被已开始自然恢复，但目前仍不清楚植被的恢复程度是否足以改变捕食者的行为响应。本研究借助激光雷达（Light Detection and Ranging，LiDAR）数据与全球定位系统（Global Positioning System，GPS）点位数据，探究了地震勘探线的植被及其他属性如何影响灰狼（Canis lupus）与灰熊（Ursus arctos）两种捕食者的移动模式。冬季时，无论植被高度如何，灰狼均会向地震勘探线移动；春季时，灰狼则会趋向植被更高的勘探线。夏季时，灰狼会选择植被更低矮的勘探线，且在植被高度低于0.7米的勘探线附近移动速度更快。春季与夏季，灰熊更偏好植被低矮的地震勘探线，但植被高度与灰熊的移动速率并无关联。上述结果表明，夏季灰狼会将地震勘探线作为移动通道；但冬季灰狼相对于勘探线的移动行为，除移动效率外，还可能受其他因素影响——例如更便捷地进入有蹄类猎物常出没的区域。灰熊既可能将地震勘探线作为移动路径，也可能将其作为获取植物性食物或有蹄类猎物的场所。若要降低灰狼的移动速率，修复工作可优先针对植被高度低于1米的地震勘探线开展。但本研究结果显示，即便在修建数十年后、植被处于较晚恢复阶段时，地震勘探线仍会对灰狼的移动行为产生影响。目前仍不清楚，在自然恢复的哪个阶段（若存在这样的阶段），灰狼会停止对地震勘探线产生行为响应。为降低灰狼对地震勘探线的响应，可评估封堵勘探线、植树造林等主动修复策略，以及替代猎物管理方案的实施效果。