Distribution and Abundance of Predators that Affect
Duck Production: Prairie Pothole Region
Predator Surveys
Livetrapping Striped Skunks
This survey was conducted in early May and consisted of setting one single-door, wire-mesh livetrap (23 x 23 x 66 cm) for 5 days in each quarter section along the center road for a maximum of 200 trap-nights (one trap set for 1 night) per study area. Traps were moved each day; trap sites in the same quarter section were >100 m apart. Trapping in each study area was conducted on consecutive days. If it was interrupted by inclement weather, it was resumed when conditions improved. Traps were baited with canned sardines and set in the most suitable sites (e.g., field edge, culvert, marsh edge, road ditch), usually <50 m from the center road. Because striped skunks are largely nocturnal (Jones et al. 1983), traps were set daily between 1700 h and sunset and checked the next morning between sunrise and 0900 h. Caught animals were released at capture sites when traps were checked. The index from this survey was capture rate (the sum of caught skunks divided by the sum of trap-nights).Livetrapping Franklin's Ground Squirrels
This survey was conducted in early July and consisted of setting four livetraps (same trap described for striped skunks) for 5 days in a cluster along each linear 1.6 km of the center road of each study area for a maximum of 200 trap-days (one trap set for 1 day) per study area. Traps were moved each day to a new site; traps in a cluster were >20 m apart and trap sites were >200 m apart. A trap site was defined as an area less than or equal to 2 ha. Trapping was conducted on consecutive days. If it was interrupted by inclement weather, it was resumed when conditions improved. Traps were baited with canned sardines and set in the most suitable sites (e.g., brush or densest available upland vegetation) <400 m from the center road. Traps were set daily between sunrise and 0900 h, left overnight, and checked the next morning during the same time period. We assumed all captures occurred during daytime because Franklin's ground squirrels are diurnal (Choromanski-Norris et al. 1989). Caught animals were released at capture sites when traps were checked. The most useful index from this survey was capture rate (the sum of caught Franklin's ground squirrels divided by the sum of trap-days). The percentage of 2.6 km2 units of each study area in which Franklin's ground squirrels were caught was useful for describing distribution in study areas.
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