In March 1999, we selected starting points for each point count transect. In June 1999, we completed laying out the remainder of each transect. To mark each transect, we used a measuring tape and a compass to walk a straight course for 250-300 m from the chosen starting point. At the end point, the map was checked to verify that the location was correct by referencing recognizable landmarks such as fence lines, road intersections, and topography. We then marked each point with a wooden stake and plastic tag on which the transect name and point number were written. A non-differentially corrected GPS fix was obtained for each point to facilitate relocating the points even if the stakes are removed.
The small mammal component was surveyed using live trap grids and transects. Spacing of live traps along transects enabled broader coverage of the area and facilitated identification of specific microhabitats which proved to be important to the successful capture of all species present.
Small mammal mark-recapture plots were established in the major coarse scale variations of the plant community: (1) a heavily grazed area close to the canal with an open tree canopy, but many shrubs (plots 1-2-3), (2) a lightly grazed area close to the gas pipeline right-of-way with high tree density and many shrubs (plots 4-5-6), and (3) a lightly grazed area, burned in the past, with low tree density, but many shrubs (plots 7-8-9) (Plate 2). Three plots were located within each variation in plant community, and placed to avoid habitat interfaces by at least 50 m. The location of each plot was random within the habitat variation, but believed representative of the overall plant community with respect to plant species composition, vegetative height and density, etc., and did not include anomalous or unique attributes. Thus, the habitat structure was homogeneous within each trapping plot. Each small mammal plot measured 40 m x 40 m, and was oriented to magnetic north. The southwest corner was marked with a wooden stake and plastic tag labeled with plot number and GPS coordinates. Within each plot, wire flags were placed at 10-m intervals resulting in a 25-point grid with the (x, y) coordinate of (1, 1) occurring at the southwest corner.
We also placed a line transect in each of the habitat variations already being sampled by plots to examine the relative effectiveness of each method. Each transect originated near a road side, and extended away from the road in a straight line for 100-110 m, with traps spaced 10 m apart, for a total of 10 or 11 traps per transect. The starting point of each transect was marked with a wooden stake and plastic tag with transect name and GPS coordinates.
Certain areas of special interest were also sampled with line transect placement of small mammal traps. These were small areas with unique plant communities, or places that due to their physical shape, did not lend themselves to plot sampling. Examples of transects include those placed along the main canal and associated seepages. These line transects consisted of 10-15 traps positioned at ~10 m intervals.
Specific areas of interest were opportunistically sampled for small mammals with small and medium (Tomahawk® #105 or similar) sized box traps placed for Neotoma species or Spermophilus species. Other sampling sites such as those used for infrared monitoring, were established after reconnaissance for suitability and animal activity.
Small Mammal Mark-Recapture Small mammal sampling was conducted in May, June, and July, and followed the guidelines of the American Society of Mammalogists (1987). One of the three plots from each variation of the plant community and selected transects were re-sampled in October 1999 to detect seasonal variation. Small Tomahawk® live-traps (Tomahawk Trap Company, Tomahawk, WI) were positioned near the corresponding wire flag denoting the 10-m spacing, and were placed facing runways, burrows, or adjacent to structures such as logs. Traps were baited with a mix of rolled oats, rolled wheat, and peanut butter, and the doors locked in the open position. In order to document species which may have been wary of the traps, an acclimation period spanning 5-6 nights preceded trapping. After acclimation, the traps were re-baited, set, and placed in exactly the same position (as during the acclimation period) for four trap nights. Traps were checked once each day at least two hours after daylight ensuring that diurnal and crepuscular species had capture opportunities. Each captured animal was identified to species, sex, and age class, and a numbered #1 monel ear tag was attached (National Band and Tag Co., Newport KY). All information was recorded on field data forms. Processing time for newly captured animals averaged three minutes from trap check to release. All recaptured animals were released after recording of tag number and capture coordinates. Capture methods and data recorded were the same for plot and transect trapping.
Infrared Monitoring We placed Trailmaster® TM1500 active infrared monitors (Trail Master, Lenexa, KS), and fully automatic 35 mm Olympus® DLX camera units (Olympus America Inc., Woodbury, New York) loaded with 24 exposures, ASA 200 slide film at several locations. Monitoring sites included wooded and open areas which were chosen after initial reconnaissance, and consisted of game trails, rock outcrops, and water sources. Monitoring began in June 1999 and continued intermittently through March 2000, during times when relatively mild weather was predicted. The transmitter and the receiver with a camera unit were attached to trees, existing posts, or stakes on opposite sides of the target area, and partially concealed with natural vegetation. The infrared beam was adjusted to pass approximately seven inches above the ground. The receiver was programmed to record an event when the pulsed infrared beam was interrupted for 0.20 seconds. This timing was to allow the legs of walking deer or pronghorn to usually pass through the beam without recording an event or activating the camera, yet still record the passing of a body approximately 10 to 20 inches tall. The receiver was also programmed for a delay of two minutes between transmitted camera signals to eliminate multiple photographs of one slow-moving target. The monitors recorded events 24 hours/day, but cameras were programmed to only accept input signals from the receivers from late afternoon until midmorning. Monitors were activated for one to sixteen nights per station (Kucera and Barret 1993, Hernandez et al. 1997). Scent and/or bait were used to attract carnivores and cause them to hesitate in the target area to permit a clear photograph. The scent was a commercially prepared compound (M&M Fur Co., Bridgewater, SD), placed on low vegetation. The bait was a large beef bone wired to a stake in the ground. Each unit was checked at least weekly to check alignment and to record event data from the receiver onto data forms. The receiver recorded date and time of each event; the camera also recorded this information on the film. By synchronizing clocks on the receiver and camera, the two systems could be integrated to match a recorded event with the corresponding photograph. This provided a back-up method for identifying the location, date, and time of each photograph.