Heard Douglas C, Zimmerman Kathryn L
Tithonus Wildlife Research, Prince George, British Columbia, Canada.
Ministry of Environment and Climate Change Strategy, Province of British Columbia, Kamloops, British Columbia, Canada.
PeerJ. 2021 Mar 9;9:e10708. doi: 10.7717/peerj.10708. eCollection 2021.
Most woodland caribou () populations are declining primarily because of unsustainable predation resulting from habitat-mediated apparent competition. Wolf () reduction is an effective recovery option because it addresses the direct effect of predation. We considered the possibility that the indirect effects of predation might also affect caribou population dynamics by adversely affecting summer foraging behaviour. If spring and/or summer nutrition was inadequate, then supplemental feeding in fall might compensate for that limitation and contribute to population growth. Improved nutrition and therefore body condition going into winter could increase adult survival and lead to improved reproductive success the next spring. To test that hypothesis, we fed high-quality food pellets to free-ranging caribou in the Kennedy Siding caribou herd each fall for six years, starting in 2014, to see if population growth rate increased. Beginning in winter 2015-16, the Province of British Columbia began a concurrent annual program to promote caribou population increase by attempting to remove most wolves within the Kennedy Siding and the adjacent caribou herds' ranges. To evaluate the impact of feeding, we compared lambdas before and after feeding began, and to the population trend in the adjacent Quintette herd over the subsequent four years. Supplemental feeding appeared to have an incremental effect on population growth. Population growth of the Kennedy Siding herd was higher in the year after feeding began ( = 1.06) compared to previous years ( = 0.91) and to the untreated Quintette herd ( = 0.95). Average annual growth rate of the Kennedy Siding herd over the subsequent four years, where both feeding and wolf reduction occurred concurrently, was higher than in the Quintette herd where the only management action in those years was wolf reduction ( = 1.16 vs. = 1.08). The higher growth rate of the Kennedy Siding herd was due to higher female survival (96.2%/yr vs. 88.9%/yr). Many caribou were in relatively poor condition in the fall. Consumption of supplemental food probably improved their nutritional status which ultimately led to population growth. Further feeding experiments on other caribou herds using an adaptive management approach would verify the effect of feeding as a population recovery tool. Our results support the recommendation that multiple management actions should be implemented to improve recovery prospects for caribou.
大多数林地驯鹿（）种群数量正在下降，主要原因是栖息地介导的表观竞争导致的不可持续捕食。减少狼（）的数量是一种有效的恢复措施，因为它解决了捕食的直接影响。我们考虑了捕食的间接影响也可能通过对夏季觅食行为产生不利影响来影响驯鹿种群动态的可能性。如果春季和/或夏季营养不足，那么秋季的补充喂养可能会弥补这种限制并促进种群增长。进入冬季时营养状况的改善以及身体状况的改善可以提高成年驯鹿的存活率，并在次年春季提高繁殖成功率。为了验证这一假设，从2014年开始，我们连续六年在每年秋季为肯尼迪 siding 驯鹿群的自由放养驯鹿提供高质量的食物颗粒，以观察种群增长率是否提高。从2015 - 16年冬季开始，不列颠哥伦比亚省启动了一项同期年度计划，试图通过捕杀肯尼迪 siding 及其相邻驯鹿群活动范围内的大多数狼来促进驯鹿种群数量增加。为了评估喂养的影响，我们比较了开始喂养前后的λ值，并与随后四年相邻的昆泰特鹿群的种群趋势进行了比较。补充喂养似乎对种群增长有增量效应。肯尼迪 siding 鹿群在开始喂养后的年份（λ = 1.06）的种群增长率高于前几年（λ = 0.91）以及未进行处理的昆泰特鹿群（λ = 0.95）。在随后四年中，肯尼迪 siding 鹿群同时进行了喂养和减少狼数量措施，其平均年增长率高于昆泰特鹿群，在那些年里昆泰特鹿群唯一的管理措施是减少狼的数量（λ = 1.16 对 λ = 1.08）。肯尼迪 siding 鹿群较高的增长率归因于较高的雌性存活率（96.2%/年对 88.9%/年）。许多驯鹿在秋季时状况相对较差。食用补充食物可能改善了它们的营养状况，最终导致了种群增长。对其他驯鹿群采用适应性管理方法进行进一步的喂养实验将验证喂养作为一种种群恢复工具的效果。我们的结果支持应实施多种管理措施以改善驯鹿恢复前景的建议。
