. The Canadian field-naturalist. Figure 3. Schematic diagram illustrating routes of Caribou involved in 10 pipeline encounter episodes from 23 July to 2 August 1971. Detailed routes are shown to illustrate avoidance of higher ( m) berms in south- east sector and pools of water in subsidence craters in northwest sector. that of Caribou encountering "topographic confine- ment" at a nearby study area (Child 1974). These areas were reclaimed by adding topsoii during April 1972, so that the Caribou then used the areas regularly (Figure 4). Most Caribou appeared wary of deflection poles
. The Canadian field-naturalist. Figure 3. Schematic diagram illustrating routes of Caribou involved in 10 pipeline encounter episodes from 23 July to 2 August 1971. Detailed routes are shown to illustrate avoidance of higher ( m) berms in south- east sector and pools of water in subsidence craters in northwest sector. that of Caribou encountering "topographic confine- ment" at a nearby study area (Child 1974). These areas were reclaimed by adding topsoii during April 1972, so that the Caribou then used the areas regularly (Figure 4). Most Caribou appeared wary of deflection poles, thermocouple planes, and boardwalks and usually avoided them. However, during 1972 a large-antlered bull walked atop the east berm for a distance of 130 m, tilting his antlers to avoid the crossarms of eight deflection poles in his path. Clearance under the cross- arms ranged from to m. He then continued a course toward an elevated ( m) effluent line, which he coursed for 56 m before lightly touching his antlers to the wooden housing 2 3 times at a point where clearance was m. He then continued to a point where clearance increased to m and passed under the line. The animal was under moderate to severe insect harassment during the episode. PRUDHOE BAY TEST SITE CARIBOU-PIPELINE ENCOUNTERS 1972. Figure 4. Schematic diagram illustrating routes used by Caribou in the 21 encounters from 15 July to 4 August 1972. Large open arrows indicate number of Caribou and direction of crossing berms, small dark arrows represent individual animal paths. Numbers in center of pipeline berms indicate maximum height (m) above grade. Note increased use of northwest sector following reclamation of subsidence craters, apparent selection of north and west berm sectors for entry, and east berm for exit. Two bull Caribou in 1971 (Figure 3) obviously avoided the combination of thermocouple housing and boardwalk in the static test area. They reacted by adopting the alarm stance, uri
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