1973 as shown in Table 1. Estimates of the 
cohort and herd dry matter intakes for 1972 and 
1973 are shown in Fig. 12. Thus, in 1972 when 
the average population on the study area was 
155 animals, an estimated 25,000 kg of dry 
matter was consumed during the study period 
(21 June to 10 August). In 1973, the population 
was considerably lower, averaging 55 animals, 
400 
200 2=-0-== 
Average Population 
(no. of animals) 
\ 
$ 
800 
600 
400 
Cumulative Harvest of Herbage (kg) 
Average Herbage Removal (kg ad!) 
20 30 10 20 30 10 
June July Aug 
Fig. 12. Predicted cumulative herbage consump- 
tion by caribou in the Prudhoe Bay study area in 
the summer of 1972 and 1973. 
ts 
and the amount of herbage consumed in the 
study period was approximately 5,400 kg. 
(d) Estimation of size of study area. The 
interpretation given to harvest values has more 
meaning to the ecosystem as a whole if intake or 
harvest is expressed per unit area and in relation 
to primary production. As stated in the methods 
section, caribou populations at Prudhoe Bay 
were usually assessed by visual observation from 
the road system. The area under surveillance, 
1.5 km on either side of the road, amounted to 
530 km? and lay between the approximate 
boundaries of 149°05’ W in the east, 148°08’ W 
in the west, 70°08’ N in the south, and 70°22’ 
N in the north (Fig. 1). However, this area 
included riverbeds, ponds, and lakes as well as 
vegetated land. To estimate the relative amounts 
of each land type in the study area, 13 transects 
(6 north-south and 7 east-west) were drawn ona 
topographic map, and the relative occurrence of 
each area noted. The results, shown in Table 16, 
indicate that approximately 54% of the study 
area (i.e., 288 square km), was vegetated in late 
July and hence was available for grazing by 
caribou. 
An effort was also made to calculate the 
total area of continuous habitat available to the 
caribou at Prudhoe Bay. An examination of 
topographic maps of the Prudhoe Bay/Beechey 
Point area suggested that the coastal tundra was 
bounded by the Kuparuk and Sagavanirktok 
rivers, on the W and E respectively, and by the 
White Hills (approximately 75 km away) and 
Table 16 
Approximate size of study areas and land classification. 
Available River bed 
Total for grazing Lakes and dunes 
Proportional 0.54 0.23 0.22 
distribution (4SE) +0.03 +0.03 40.04 
Study site (km?) 532 288 124 119 
(Prudhoe Bay) 
Kuparuk/Sagavanirktok 2842 1540 665 637 
River drainages (km?) 
Proportional distribution of land type was determined as fractional occurrence of each on 13 line transects drawn on a 
topographical map. 
Study site includes all land visible 1.5 km either side of the Prudhoe Bay road system. 
River drainage is bounded by the White Hills and Franklin Bluffs to the SE and S. 
