Geoscience Reference
In-Depth Information
arate. The stock from the Front is twice as large as the gulf stock, a difference probably related to the available
whelping habitat.
Formation of ice at the Front is a complex process. It thickens gradually, transformed from pancake ice and
a slushy mixture called “northern slob” into young ice, still too thin to support seals, and finally into the regu-
lar winter ice. This first winter ice provides both the necessary stability as well as leads, which the seals re-
quire to penetrate to whelping sites. Breathing holes are found in these leads between floes and are kept open
by the seals until the ice becomes thick enough for them to climb out onto it. Whelping ice is normally 50 cen-
timeters (20 inches) thick and somewhat hummocked. It appears that harp seals prefer this type of ice to thin
flat ice, since the hummocks and hollows provide protection for the pups from the wind. The females haul out
onto the winter pack ice in late February or early March and give birth several days later. Individual herds usu-
ally divide into two main “patches,” covering an area of 20 to 200 square kilometers (8 to 80 square miles) and
containing as many as two thousand adult females per square kilometer.
The newborn pups weigh about 11 kilograms (24 pounds) and are yellowish. Within three days, their fur
turns to a fluffy white, earning them the nickname “whitecoats.” Young harp seals are among the fastest grow-
ing and most precocious of young mammals. During the brief nursing period of twelve days, they triple their
weight on the 45 percent fat content of their mother's milk. Mothers frequently leave their pups during this
period but relocate them by odor and perhaps by the distinctive call of the pup. Once abandoned, the pups be-
gin to molt, replacing their white coat with a short silvery one flecked with dark spots. Following weaning, the
pups fast for four to five weeks and may lose a third of their body weight. It is believed that this period is a ne-
cessary developmental stage, allowing the pups time to develop the physical and behavioral skills necessary
for them to forage on their own.
As soon as the females leave the “whelping patch,” they are courted by males that have been waiting nearby.
The fertilized embryo is not implanted until early August, however, which ensures that the pups will be born at
the time of year when ice conditions are likely to be favorable. Ice conditions likely trigger whelping, since in
years of reduced ice formation whelping is delayed. Whelping also occurs as the winter ice formation is ending
and lasts only long enough to sustain the pups while they grow and become self-sufficient. In years when there
is poor ice formation in the Gulf of St. Lawrence, gulf breeders move northward as far as the Front to find suit-
able ice conditions.
A month after whelping, in early April, both mature and immature seals undergo the annual molt, at the
southern edge of the icefields, to replace their fur. Adult males and the young molt first, followed by the ma-
ture females. During the molting period, adults rarely eat and may lose up to 20 percent of their body weight.
Once the molting process has finished, they depart for their summer feeding grounds, working their way along
the Labrador coast and feeding on capelin as they go. Small numbers will summer in northern Labrador, but
most will move farther north, arriving along the southwest coast of Greenland in early summer, where they be-
gin to feed heavily on capelin to replenish lost stores of fat. Younger animals appear to move farther northward
along the coast as the season progresses, and in fact, most of the summering animals in Greenland are either
juveniles or young of the year. Some animals also pass through Hudson Strait into Hudson Bay, penetrating as
far as the Belcher Islands, at the top of James Bay. More seals move up the west side of Davis Strait, however,
to utilize shore leads such as in Cumberland Sound, on the west side of Baffin Island.
When these inner sounds begin to freeze up in early November, they retreat to southern Cumberland Sound.
Numbers build in Frobisher Bay in late November and early December, and by late December both adults and
juveniles are again passing through northern Labrador waters, on their way to the whelping grounds.
Harp seals were the basis of an intensive seal industry beginning in the early 18th century. The heyday of
the seal hunt was in the early 19th century, when it was not uncommon for a half million pelts to be harvested
annually. Most were whitecoat harp seals, though some adult and juveniles were taken as well as a small num-
ber of hooded seals. Catches declined in the late 19th century, despite the advent of steam-powered ships. By
