170 
Table 13 
Mean rates of forage collection from esophageal fistulated reindeer. A collection period was 
started when the reindeer terminated its lying period; esophageal samples were collected 
over a timed interval of 14-20 min. 
Mean (+SE) rate of 
Vegetation Sample Number of dry matter collection CV 
type identification observations (g/min) (%) 
Eriophorum polygon marsh 1-7 7 2.54+0.35 36 
Dryas heath and snowbeds 9-12 4 3.24 + 0.94 58 
Dupontia brook/meadow 14-17 4 2.36 + 0.40 34 
Carex marsh Sas 2 2737 + Ae26 75 
Sand dunes (Salix ovalifolia) 19, 20 2 5.30+1.76 47 
Total 1-7, 9-20 19 2'92:+0)35 52 
CV = coefficient of variation (SDx100/mean). 
Fig. 10. Relationship between rate of eating, as 
estimated by collection of esophageal egesta, 
and available live biomass (a). Forage samples 
were collected over a 10 min period following 
3-4 hr fasting. Theoretical relationships between 
percentage of day spent eating and availability 
of live biomass (b). The general relationship was 
adapted from data for grazing sheep (---, Young 
and Corbett, 1972). YZZZ,, average available live 
biomass at Prudhoe Bay in July (see Fig. 9). 
Esophageal Egesta Collection 
g DM (100 kg BW)! min"! 
O 20 40 60 80 
Live Biomass (g DM m2 ; 
2 ) Unfortunately, we have no comparable detailed 
estimates for adult males. However, we have 
estimates of the grazing intensities of these 
cohorts (Table 14) which show that lactating 
caribou graze more intensively than non-lactat- 
ing female caribou and caribou bulls. If it ts 
assumed that all cohorts spend the same propor- 
tion of the day grazing (where grazing time = 
eating time + searching time), then estimates can 
be made of the relative amount of time spent 
eating (Table 14). This may be an oversimplifica- 
tion of grazing behavior under natural condi- 
tions, for it is known that the amount of time 
ruminants spend grazing decreases exponentially 
with increasing available biomass (Young and 
f) 20 40 60 80 100 Corbett 1972). Since we were unable to deter- 
Live Biomass (g DM m2) mine this parameter, the general form of a 
relationship between grazing time and biomass 
Percentage of Day Spent Eating 
