158 
Table 2b 
Comparison of activity patterns of calf and adult 
cohorts at Hardangervidda and Prudhoe Bay. 
Calves, Calves, 
reindeer caribou 
(1-10 d) (3-4 wk) 
Grazing 7% 24% 
Lying 66% 55% 
Standing 9% 5% 
Walking 12% 11% 
Trotting 2% 5% 
Running 2% 2% 
Suckling 4% <1% 
Reference: 
Hardangervidda 
Thomson (1973) (Table 2a) 
reindeer in Norway; Thomson 1973). The gradu- 
al development of the Aangifer calf activity 
towards an adult pattern is illustrated in Table 
2b. 
Nursing behavior 
A total of 55 successful suckling events were 
observed over the 6 wk study period in 1972, 
35% of which were timed at between 10 to 85 
sec duration (mean 33.3 sec). At the start of the 
study, calves were approximately 2-4 wk of age, 
assuming calving to be approximately June 8 
(Lent 1966; Calef and Lortie 1973), and they 
were suckled significantly (P <0.05) longer than 
calves at 6-7 wk of age (Table 3). These data 
confirm observations on wild reindeer in Nor- 
way and domesticated reindeer in Sweden. The 
general ontogeny of nursing behavior for mem- 
bers of the genus Rangifer is shown in Fig. 3. 
Unlike reindeer, in which a lactating female may 
nurse several calves at one event, only single 
nursing events were observed in caribou. 
In a separate study on milk production of 
reindeer (White, Holleman, and Luick, unpub. 
Table 3 
Duration of single nursing events (4SD) of caribou 
calves at Prudhoe Bay. 
Age of calf Duration Significance of 
(wk) (sec) difference 
3-4 36.0+7.3 
P<0.05 
6-7 26.7+4.4 
Prudhoe Bay 
Adult Adult 
caribou reindeer 
(insect-free, July) (insect-free, August) 
53% 49% 
33% 30% 
1% 3% 
11% 14% 
2% 3% 
<1% 3% 
Hardangervidda 
Thomson (1971) 
Prudhoe Bay 
(Figure 4) 
obs.), it was shown that milk intake of reindeer 
calves was 1.5-2 1d°' for the first 2 weeks of 
age, after which it declined exponentially, viz. 
M=2.1 Be 0.01 16A 
where M = milk intake (1d°') and A = age of calf 
(d). 
Insect harassment 
(a) Relationship of insect harassment with 
wind and temperature. Insect harassment was 
observed to have a dominant influence on cari- 
bou social behavior, as evidenced by changes in 
gregariousness, activity times, speed of move- 
ment, and habitat selection. The presence and 
degree of insect harassment on caribou could be 
recognized (and classified as moderate or severe) 
© Sweden, Espmark (1971) 
100 OD Norway (Hardangervidda) 
@ USA (Prudhoe Bay) Interval 
80 between successful 
: sucklings 
Duration (min) 4 
of 60 300 
suckling 
(sec) 
(ela! ) 40 200 
20 100 
(0) O 
(0) 4 8 l2 16 20 
Approximate age of calves (wk) 
Fig. 3. Comparison of the ontogeny of suckling 
behavior in domesticated (0) and wild (Q) 
reindeer and caribou (@). 
