Off-channel aquatic habitat use by river otters and other vertebrates in the Central Platte River Valley, NE

We employed a multi-camera non-linear array sampling design to understand river otter habitat-use patterns in natural and artificial off-channel wetlands along the Platte River. We surveyed 10 off-channel aquatic habitats between 13 February to 15 October 2019. The sites were comprised of 5 pond and 5 slough sites. Each site consisted of a 100-130-meter non-linear array of 3 camera traps placed on existing wildlife trails along the banks of an off-channel aquatic habitat. Individual cameras were spaced between 40 and 75 meters apart within each array, depending upon conditions (availability of animal trails and appropriate topography). Habitat variables were collected at two spatial scales including the macrosite (broader aquatic environment; n = 10) and the microsite (trail along terrestrial-aquatic boundary; n = 30). In addition to documenting river otter occurrences, we recorded all identifiable vertebrate species from camera trap surveys. Therefore, this database has habitat modeling value for a range of other species including mammals such as the American Mink (Neovison vison), American Beaver (Castor canadensis), and Muskrat (Ondatra zibethicus) as well as birds such as the Great Blue Heron (Ardea herodias) or Canada goose (Branta canadensis). Some habitat variables are congruent across spatial scales and others differ. Macrosite habitat variables included maximum and average water depth (m), total water surface area (ac), water pH, water total hardness, mean distance to the river (m), mean distance to dirt road (m), mean distance to paved road (m), mean distance highway (m), mean distance to building (m), mean distance to woodland (m), mean vegetation cover across multiple height classes, the proportional cover of graminoids, forbs, woody species, and groundcover as litter. Microsite variables included all the same distance and vegetation cover metrics but also included bank slope, bank height (m), and control variables like the trail camera height and distance of the camera to the trail. The wetland depth profile was not considered at the microsite level as it reflected features of the larger waterbody. We included river otter scat detection as a validation technique for our river otter relative use metrics which included river otter presence/absence, total river otter captures per camera month, river otter young presence/absence, and river otter young captures per camera month.

本研究采用多相机非线性阵列采样设计，旨在探明普拉特河（Platte River）沿岸自然与人工河道外湿地的水獭（river otter）栖息地利用模式。本研究于2019年2月13日至10月15日，对10处河道外水生栖息地展开调查，其中5处为池塘生境，5处为河漫滩沼泽（slough）生境。每处生境布设1组100~130米长的非线性阵列，阵列内沿河道外水生栖息地岸带的现有野生动物步道设置3台红外相机（camera trap）；每组阵列内的相机间距为40~75米，具体间距根据现场条件（野生动物步道可获得性与适宜地形）灵活调整。

本研究在两个空间尺度下采集生境变量：大尺度生境（macrosite，即广义水生环境，共10处）与微尺度生境（microsite，即水陆交界步道，共30处）。除记录水獭的出现情况外，本研究还通过红外相机调查记录了所有可识别的脊椎动物物种。因此，本数据集可为多个其他物种的生境建模提供支撑，涵盖哺乳类（如美洲水貂（Neovison vison）、北美海狸（Castor canadensis）、麝鼠（Ondatra zibethicus））及鸟类（如大蓝鹭（Ardea herodias）、加拿大黑雁（Branta canadensis））。

部分生境变量在两个空间尺度下具有一致性，其余变量则存在差异。大尺度生境变量包括：最大水深与平均水深（单位：米）、总水面面积（单位：英亩（ac））、水体pH值、水体总硬度、至主河道的平均距离（单位：米）、至土路的平均距离（单位：米）、至铺装路的平均距离（单位：米）、至高速公路的平均距离（单位：米）、至建筑物的平均距离（单位：米）、至林地的平均距离（单位：米）、多高度层平均植被盖度、草本植物（graminoids）、杂类草（forbs）、木本植物的占比盖度，以及枯落物地表覆盖度。微尺度生境变量除包含上述所有距离与植被盖度指标外，还包括岸坡坡度、岸高（单位：米），以及相机架设高度、相机至步道的距离等控制变量。由于湿地水深剖面反映的是更大水体的特征，因此未在微尺度生境下采集该变量。

本研究采用水獭粪便检测作为水獭相对利用强度的验证方法，水獭相对利用强度指标包括：水獭存在/缺失情况、单相机月均水獭触发次数、幼獭存在/缺失情况，以及单相机月均幼獭触发次数。