Models ACTIVE and GRAZE have been 
used in preliminary investigations (F. L. Bunnell, 
R. G. White, and D.E. Russell, unpub. obs.). 
From gaming runs with model ACTIVE, we 
predict that periods of severe insect harassment 
of more than 2 hr duration could increase the 
daily heat production by 1.6 to 3 times the 
average daily metabolic rate estimated for an 
insect-free day. It will be used in future studies 
to investigate harassment problems and, hope- 
fully, to predict energy costs of harassment by 
human, vehicle, and aircraft interference in 
theoretically ‘‘habituated” and ‘‘non-habituat- 
ed”’ caribou populations. 
Model GRAZE is being used to investigate 
the range of possibilities that exist for caribou to 
select vegetation types, plant groups, and plant 
species at Prudhoe Bay. For example, what 
would be the expected change in grazing pattern 
and food intake if caribou were selectively graz- 
ing plants high in protein, phosphorus, or energy 
rather than selecting those of highest digestibil- 
ity? Model GRAZE will also be useful in predict- 
ing the rate of diminution of plant biomass in 
the event of inadvertent or planned holding of 
caribou on the Prudhoe Bay development. 
Model GROWTH is still in the coding stage. 
As soon as it has been interfaced with models 
ACTIVE and GRAZE, an attempt will be made 
to set limits on the upper stocking capacity 
which will ensure, firstly, a sustained population 
and, secondly, a sustained yield for this area. 
Discussion 
This project did not aim at determining the 
year-round population dynamics and movement 
of caribou at Prudhoe Bay. Hence, the herd or 
herds (Arctic or Porcupine) to which these 
caribou belong in the study years remains un- 
known. Our own studies on behavioral patterns, 
combined with local observations on the pres- 
ence of animals on a year-round basis, indicate 
that there are two caribou populations at Prud- 
hoe Bay. One may be considered resident, the 
other migratory. The resident herd is probably 
small in number, perhaps 5-30 being visible from 
the road system during most seasons. They also 
appear to become habituated to traffic on the 
road system, unlike the migratory animals. 
Based on an extrapolation of 55 animals in the 
study area, it is suggested that the maximum 
181 
“resident’’ population may be 300 animals oc- 
cupying the draining basin of the Kuparuk and 
Sagavanirktok rivers and bordered on the south 
by the Franklin Bluffs and. the White Hills 
(Fig. 1). This is a total tundra area of approxi- 
mately 2,840 km? (Table 18). The approximate 
stocking rate would be 0.1 caribou km? (0.3 
caribou mile?) or 10 km? (3.9 mile?) per cari- 
bou. This density is low compared with esti- 
mates of 1-3 caribou mile? for the Arctic, 
Porcupine, and Kaminuriak herds (Calef 1974), 
and must be considered a minimal estimate for it 
does not include the peak influx of migratory 
animals. The upper limit may be set by the 
availability of winter range because separate 
studies at Prudhoe Bay show that although there 
are a large number of lichen species, their actual 
distribution is limited to the dry habitats, and 
except for a peak biomass on one habitat of 88 g 
m2 the biomass is generally low (0-55 g m*) 
(Williams et al., this volume). Therefore, resident 
caribou would have to supplement their winter 
diet with sedges, grasses, herbs, and willows in 
the more exposed communities. Again, the 
biomass would be small; plant material of high 
digestibility may be available at only 7-20 g m°. 
Dead material of much lower nutrient status 
would be present at 60-110 g m? (Table 12). A 
possible alternative source of winter range may 
be available on the Franklin Bluffs and in the 
White Hills. 
In previous years large groups of caribou 
have been observed overwintering in the central 
arctic region (Collins 1937, cited by Skoog 
1968: Olsen 1959, cited by Child 1973), and the 
same region is a calving area (Skoog 1968; Child 
1973). Hence, in some years the “‘resident’”’ 
population of caribou may be up to 10 times the 
assumed number (ca. 300) in this study. 
In summer 1972 an average of 155 caribou 
were noted in the study area, and by extrapola- 
tion to the entire river drainage system, it was 
suggested that ca. 900 used the coastal plain at 
Prudhoe Bay. This number is only one-third of 
the peak numbers (ca. 3,000) reported by Child 
(1973). However, these latter reports were for 
animals moving through the area under insect 
harassment and presumably originating from 
outside the Kuparuk/Sagavanirktok drainage 
area. While it is not appropriate to base foraging 
and energy flow calculations on this peak num- 
ber of animals, it may be appropriate to extrap- 
