Department of Fisheries and Wildlife, Oregon State University, Corvallis, OR, United States of America.
Arctic National Wildlife Refuge, United States Fish and Wildlife Service, Kodiak, AK, United States of America.
PLoS One. 2019 Sep 10;14(9):e0222085. doi: 10.1371/journal.pone.0222085. eCollection 2019.
Aerial surveys are often used to monitor wildlife and fish populations, but rarely are the effects on animal behavior documented. For over 30 years, the Kodiak National Wildlife Refuge has conducted low-altitude aerial surveys to assess Kodiak brown bear (Ursus arctos middendorffi) space use and demographic composition when bears are seasonally congregated near salmon spawning streams in southwestern Kodiak Island, Alaska. Salmon (Oncorhynchus spp.) are an important bear food and salmon runs are brief, so decreases in time spent fishing for salmon may reduce salmon consumption by bears. The goal of this study was to apply different and complementary field methods to evaluate the response of bears to these aerial surveys. Ground-based counts at one stream indicated 62% of bears departed the 200m-wide survey zone in response to aerial surveys, but bear counts returned to pre-survey abundance after only three hours. Although this effect was brief, survey flights occurred during the hours of peak daily bear activity (morning and evening), so the three-hour disruption appeared to result in a 25% decline in cumulative daily detections by 38 time-lapse cameras deployed along 10 salmon streams. Bear responses varied by sex-male bears were much more likely than female bears (with or without cubs) to depart streams and female bears with GPS collars did not move from streams following surveys. Although bears displaced by aerial surveys may consume fewer salmon, the actual effect on their fitness depends on whether they compensate by foraging at other times or by switching to other nutritious resources. Data from complementary sources allows managers to more robustly understand the impacts of surveys and whether their benefits are justified. Similar assessments should be made on alternative techniques such as Unmanned Aerial Vehicles and non-invasive sampling to determine whether they supply equivalent data while limiting bear disturbance.
航空调查通常用于监测野生动物和鱼类种群,但很少记录对动物行为的影响。30 多年来,科迪亚克国家野生动物保护区一直在进行低空航空调查,以评估科迪亚克棕熊(Ursus arctos middendorffi)在阿拉斯加科迪亚克岛西南部鲑鱼产卵溪流附近季节性聚集时的空间利用和种群组成。鲑鱼(Oncorhynchus spp.)是熊的重要食物,鲑鱼洄游时间短暂,因此捕鱼时间减少可能会减少熊对鲑鱼的消耗。本研究的目的是应用不同的和互补的野外方法来评估熊对这些航空调查的反应。一条溪流的地面计数表明,62%的熊在航空调查时离开 200 米宽的调查区,但在仅三小时后,熊的数量就恢复到调查前的丰度。虽然这种影响是短暂的,但调查飞行发生在熊每天活动的高峰时间(早晚),因此三小时的干扰似乎导致沿 10 条鲑鱼溪流部署的 38 个延时摄像机的累积日检测次数减少了 25%。熊的反应因性别而异,雄熊比雌熊(有或没有幼崽)更有可能离开溪流,而带有 GPS 项圈的雌熊在调查后没有离开溪流。虽然被航空调查驱赶的熊可能会减少鲑鱼的摄入量,但这对它们的适应度的实际影响取决于它们是否通过在其他时间觅食或转向其他营养丰富的资源来补偿。来自补充来源的数据可以让管理者更全面地了解调查的影响,以及它们的好处是否合理。还应该对替代技术(如无人机和非侵入性采样)进行类似的评估,以确定它们在限制熊干扰的同时是否提供了等效的数据。
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