Small mammal monitoring on Herschel Island and Komakuk Beach

We monitor lemming abundance using three methods. (1) Absolute abundance estimation by capture-mark-recapture. This involves live trapping animals using Longworth traps on three, 2 to 9 ha grids (50 to 256 traps/grid) in wetland and mesic habitats; trapping sessions last for 2-3 days and are repeated up to three times during the summer from early-June to mid-September. We also determine the reproductive condition of all captured animals. (2) Full counts and mapping of lemming winter nests after snow-melt (early June) on our absolute abundance live-trapping grids. (3) Relative abundance estimation by live-trapping (Longworth traps) on four 300 m long transects with 3 traps at stations 15 m apart along each transect. Transects are run for approximately 48 hours, in each of two seasons: spring (early to mid June) and fall (late August or Sept). We also investigate the role of snow cover and depth in habitat selection by lemmings using snow fencing to enhance snow depths on an experimental trapping grid. Snow fencing (1 m high) is erected in parallel lines c. 40 m apart and perpendicular to the prevailing wind, and traps a great deal of extra snow. The intensity of lemming habitat use is measured through the density of lemming winter nests as mapped on the experimental and a control grid just after snow melt in spring. ** If data are downloaded and used for analyses, it would greatly be appreciate that the principal investigator be informed.

本研究采用三种方法开展旅鼠种群丰度监测。
(1) 基于标记重捕法（capture-mark-recapture）的绝对丰度估算。该方法使用朗沃思诱捕笼（Longworth traps），在湿地与中生境（mesic habitats）内的3个2至9公顷样地（每个样地设置50至256个诱捕笼）中开展活体诱捕；诱捕周期持续2至3天，每年夏季（6月初至9月中旬）最多重复开展3次。同时，我们将对所有捕获个体的繁殖状态进行检测。
(2) 在上述绝对丰度活体诱捕样地中，于融雪后（6月初）开展旅鼠冬季巢穴的全计数与测绘工作。
(3) 基于活捕法的相对丰度估算：设置4条长300米的样线（transects），每条样线上每间隔15米设置1个捕位点，每个捕位点放置3个朗沃思诱捕笼。每条样线的诱捕时长约为48小时，分别在两个季节开展：春季（6月初至6月中旬）与秋季（8月末或9月）。
此外，本研究通过在实验性诱捕样地中布设雪障以增加积雪深度，探究积雪覆盖与积雪深度对旅鼠生境选择的影响。雪障高1米，以与盛行风向垂直的方向平行布设，间距约40米，可截留大量额外积雪。在春季融雪后，通过对实验样地与对照样地的旅鼠冬季巢穴进行测绘并统计其密度，以此量化旅鼠对生境的利用强度。
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