Reindeer feeding after a heavy snowfall.
Photo: Inger Marie Gaup Eira/www.ealat.org
The snow-loving deer of the Arctic
movement during spring migrations. Under severe conditions,
calves are born before the herds arrive at the calving grounds.
Reindeer and caribou (Rangifer tarandus) have been called In such years, up to 40 per cent of calves can die before they are
chionophiles, snow loving. In fact, Arctic island subspecies of a month old
76
. In northwestern North America, recent warming
Rangifer are associated with a snow environment for up to ten has led to a dramatic increase in the number of days of above
months out of the year. Rangifer are the most dominant large freezing temperatures during the Rangifer migration period.
mammal species in Arctic environments. The species has spe- Thawing and subsequent re-freezing of snow results in ice lay-
cialized adaptations in order to thrive in a cold environment. ers in the snow pack which hinder travel of Rangifer and make
Their diet is energy rich winter lichen, which they obtain mostly it harder to crater for food
76
. There have been catastrophic de-
by digging (cratering) under the snow
70,71
. Large hooves aid in clines in the Peary caribou on the Arctic islands of North Amer-
the cratering and allow Rangifer to better travel through snow
72–74
. ica and they are now considered endangered (Figure 4.9). The
Rangifer are the only member of the deer family in which both formation of ice layers that prevent the caribou from accessing
males and females grow antlers. Pregnant females retain their food has been identified as the chief cause of the declines
77,78
.
antlers until after spring-time calving, allowing them to domi-
nate the social hierarchy in late winter. This dominance allows
them to displace lower ranked animals from feeding craters,
Population
saving valuable energy
75
. The large migratory herds of Rangifer
size
migrate north into regions of rapidly melting snow in spring
40 000
during the calving period. The pregnant and birthing cows
feed along the snow-melt line, and the newly emerged forage
30 000
that they ingest is highly digestible, protein-rich and critical for
milk production.
20 000
Although under normal conditions Rangifer are able to thrive
10 000
in snow environments, snow can also severely limit the annual
productivity of herds. During deep snow years, more energy is
expended in digging to the lichens than is derived from eat-
0
1961 1975 1989 2004
ing them, so caribou limit cratering or move in search of more
favourable snow conditions
75
. Under deep snow conditions,
Figure 4.9: Population size of Peary caribou in the Canadian Arc-
Rangifer severely deplete their fat and protein reserves to meet
tic islands from 1961 to 2004, showing major declines.
their daily energy needs. Late snow melt and deep snow stalls Source: Based on data from D. Russell
52 GLOBAL OUTLOOK FOR ICE AND SNOW