Seals
Ringed Seal
There
are a wide array of Inuit names that are used to describe the ringed seal
(Phoca
hispida). Some of these
include: "netsiak" (whitecoat), "netsiavinerk" (silver jar), "netsilak"
(adult), and "tiggak" (breeding male).
The common name refers to the circular markings on the back of
the adult. The scientific
name refers to the seal's bristly coat.
 The
ringed seal is the smallest pinniped in the Canadian Arctic.
Newborn pups average 4.5 kg in weight and 65 cm in length.
When one year old, they are about 70 per cent of their mature
size. The average adult is
135 cm long and weighs about 70 kg.
Females tend to be slightly smaller than males. The
number of ringed seals in the Western Arctic, including Amundsen Gulf, is
approximately 650 thousand seals. The fluctuation of the ringed seal
population numbers are linked to polar bear population numbers. This
seal is found throughout the circumpolar regions of the Northern Hemisphere.
Its preferred habitat consists of the leads, pressure ridges and polynyas
in the land-fast ice of the Arctic Ocean. The
offshore pack ice is used irregularly.
 Primarily
solitary, the ringed seals occasionally travel in loosely organized groups. They tend to form aggregates at haul-out areas, such as ice cracks. Segregation by age occurs in winter when adults remain in
preferred breeding habitat under stable ice in bays and fiords and non-breeders
are found at the flow edge and move in response to food availability and
population pressures.
Ringed
seals have a varied diet composed primarily of the larger shrimp-like
crustaceans (e.g., Parathemisto, Mysis), small fish (e.g., arctic cod) and
planktonic krill. Fasting occurs
during the moulting and basking periods.
As
with most seals, physiological adaptations, such as a high red blood cell count,
the ability to reduce their heart rate from 80 - 90 beats per minute to 10 - 20,
and control over the blood flow to vital organs, have enabled ringed seals to
make deep and sustained dives. Feeding
dives average 3 minutes with 1½ minutes at the surface. Their maximum diving potential is about 90 m and 45 minutes.
Ringed seals dive vertically, tail first, rarely exposing their backs.
Breathing
holes in ice up to 2½ m thick are maintained by clawing the ice with the
foreflippers. Before surfacing, a
seal may blow bubbles into the hole to test for predators. The breathing hole is cone-shaped and covered with an ice
dome punctured by a small vent. If
snow drifts over the hole, a lair may be hollowed out of it.
Their
senses of vision, hearing, and smell are well developed.
Vocalizations include whines, moans and growls.They are curious and may investigate unfamiliar sights or sounds. Basking seals constantly alternate between lifting their heads up for
about seven seconds and laying flat for 26 seconds. They heed warnings from other seals.
Seal
pups are usually born on stable ice in a snow den from mid-March to early April.
The female finds a natural snow cave or excavates a birth lair in a
snowdrift over a breathing hole. The
den provides protection and warmth for the single pup during a five to eight
week nursing period. Only the
female cares for the pup. She
abandons it when the ice breaks up. Large
numbers of seals can be observed basking on the ice at this time, usually in
late June or early July.
The
pup is born with a fine-textured woolly white coat or lanugo, which keeps the
pup warm until it acquires an insulating layer of blubber. The lanugo is shed by the age of eight weeks.
The moulted pup, which is called a "silver jar", has a silvery
belly and a dark grey back of fine hair. The
adult's coat is made of stiff guard hairs and occurs in various colour patterns.
The underside may be silvery white to creamy yellow with a scattering of
black spots while the back is dark grey marked by grey-white rings.
By
counting annual growth rings in the dentine layers of their teeth, the oldest
recorded age for a ringed seal is 43 years.
Sexual maturity occurs between the ages of five and ten.
After ten years of age the females have a high annual pregnancy rate.
Breeding males have a strong, musky odour and may be territorial.
The peak of mating activity is in April and the embryo development is
delayed for 81 days followed with a 9-month gestation period.
Little
is known about diseases in seals. Some afflictions include skin diseases, pneumonia and numerous parasites. Residue concentration of
organochlorides, such as PCB's, DDT and DDE are
found in seal blubber at low levels. Seal liver may contain high levels of mercury.
Predators
of ringed seals include polar bears, arctic foxes, walrus, wolves, dogs,
wolverine, sharks, gulls and humans. About
26 per cent of the pups in their dens are eaten by arctic foxes. Ringed seals are the main prey of polar bears that catch about one seal
every six and a half days.
The
cultural development of coastal Inuit was supported by the ringed seal.
They were a reliable supply of heating oil, meat and skins. Various hunting techniques include the stalking of basking
seals, harpooning or shooting at breathing holes, and open water shooting. Sealing continues to be important for its nutritional and cultural values
to northerners.
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