Off-channel aquatic habitat use by river otters and other vertebrates in the Central Platte River Valley, NE
Description
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.
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Steps to reproduce
Off-channel aquatic habitat included excavated ponds, resulting from sand and gravel mining, and groundwater fed sloughs. All sites assessed during the study were at the Crane Trust’s main conservation complex in Hall County, Nebraska, USA (Easternmost site = 40.794331°N, -98.401224°W, 579 m elev.; Westernmost site = 40.780611°N, -98.477476°, 586 m elev.). Microsite survey locations were selected via preliminary visual assessments of off-channel habitats outside of the growing season as this allowed for easier identification of semi-aquatic mammal trails. Cameras were placed within 5 m of aquatic habitats along these trails. We utilized ten types of trail cameras for reasons of availability including Reconyx HyperFire HC600 and UltraFire XR6 (Reconyx, Holmen, WI, USA), Muddy Pro-Cam 14 (GSM Outdoors, Irving, TX, USA), Stealth Cam STC-1890 (GSM Outdoors, Irving, TX, USA), Moultrie M-50i and M-880 (Moultrie Feeders, Calera, AL, USA), Cuddeback F2 (Cuddeback, De Pere, WI, USA), Browning SpecOps Extreme (Browning Trail Cameras, Birmingham, AL, USA), Busnell HD Trophy Cam (Bushnell, Overland Park, KS, USA), and Wildgame Innovations Micro Crush X8 (GSM Outdoors, Irving, TX, USA). Cameras took 1 image with a 1-minute delay between images per motion sensor trigger, with a subset of cameras set to record time-lapse photos (interval = 15 min) as well as a validation. We placed multiple camera types within each array to account for differences in wildlife detection capabilities. Vegetation data was collected every meter across three different height classes (<0.5 m, 0.5 < 2.0 m, > 2.0 m) along parallel transects on either side of the wildlife trail using a line-point-intercept vegetative survey method. Transects ran from the water’s edge to 5 m inland. Growth habits were derived from USDA classifications for particular species. Habitat distance measurements within 400 meters were estimated with a Nikon Laser 800 (6 x 216.0°) rangefinder (Nikon, Tokyo, Japan). Longer distance and area measurements were made using 2016 Landsat imagery and the measure tool in Google Earth Pro version 7.3. Several water-related variables were only collected at the macrosite level including maximum and mean water depths. Slough depths were estimated by sampling every 10 m from a random starting location down the center of sloughs for the length of trapping arrays. Pond depths were sampled every 10 m via multiple transects placed every 50 m across the length and width of ponds using a kayak and weighted measuring tape. Water pH and total hardness were assessed using “multi-purpose 6-way test [water quality indicator] strips” (HTH brand, Sigura, Alpharetta, GA, USA). All efforts were made to keep trail camera height and the distance of cameras to wildlife trails constant. However, we included trail camera height and its distance to each wildlife trail as independent variables in our microsite investigations. Bank height and bank slope were only recorded at the microsite level.
Institutions
- Auburn University
- International Crane Foundation