The
narwhal is a "toothed whale" and a relative to the sperm whale, pilot
whales and dolphins and porpoises. It is unusual among the whales, as it
has no dorsal fin, and its neck vertebrae, instead of being fused together,
are joined like those of land mammals. The dorsal fin may have been lost
because it was a hindrance under the ice. It has small rounded, up-curved
flippers. Among the toothed whales, the narwhal is large: average males
weigh about 1.6 tonne and are about 4.6 m long, females weigh about 0.9
tonne and are about 4.0 m long. Narwhals have blunt heads and small mouths.
The narwhal is insulated from the freezing waters by a layer of blubber
- fatty tissue under the skin - up to 10 cm thick,
Narwhals
have no functional teeth. Two elongated teeth develop in the upper jaw,
but they point forwards, not down into the mouth. In females, both usually
remain embedded in pockets in the maxillary bone and grow no longer than
15 cm or so, but in males and very few females, the left one erupts through
the lip and develops as a straight, spiral tapered tusk, with a left-hand
twist, 2.0 - 2.8 m long. Monodon monocerus means "the one toothed animal
that looks like a unicorn". Some males also grow a tusk on the right side.
Usually shorter than the other one, an abnormal tusk grows out of the tip
of the lower jaw of the narwhal. |
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Copper engraving of twin narwhal tusk.
"News from Iceland, Greenland
and the Strait
of Davis by Johan Anderson,
Hamburg, 1746" |
After the
tusk has reached its final length, its walls continue to thicken inwardly,
as the living pulp runs the full length of the hollow tusk.
Perhaps
narwhal tusks arriving in Europe by little used trade routes originated
the legend of the unicorn; certainly as trade routes improved in the Middle
Ages, thousands of narwhal tusks were sold for more than their weight in
gold in Europe as unicorn horns or "alicorns", for their supposed magical
properties, by traders who were at some pains to suppress the knowledge
that these fabulous panaceas were no more than whales' teeth.
It
is still uncertain whether the tusk is more to the male narwhal than an
advertisement of mature sexuality. |
It
has been suggested that the narwhal uses it for spearing fish, stirring
up the bottom, breaking ice, as a wave guide for its underwater vocalizations
and even for popping itself on an ice flows to go to sleep. Broken and
worn tusks are common, but this probably shows no more than the difficulty
of taking care of 7 feet of ivory when chasing food near the bottom
in dark water. That it is not needed for survival is shown by the female'
s not having one. It may be used by the males in fighting for females,
but as mating takes place in spring when narwhals are in the offshore pack
ice, their mating behavior is unknown. Some scars found on the foreheads
of mature males have been cited as evidence for this use, and so have such
findings as a tusk point once discovered embedded in a male' s jaw beside
the root of the growing tusk. Males are seen in summer lifting their tusks
out of the water and crossing them with the tusks of one or two other males;
but whether this "tusking" has to do with establishing social dominance,
or just passing a summer afternoon, is unknown.
Females
probably start bearing calves at 6 - 8 years of age. They mate in April
- May, and gestate for 14 months, bearing their calves in June - August
of the following year. Like all other marine mammals, narwhals have only
one calve at a time. The newborn calves have only very thin blubber, but
mother' s milk is rich in fat and a thicker blubber layer is soon laid
down. Calves are nursed for 20 months. The association of mother and calve
is usually close, and when the whales are traveling the calf remains close
to the mother' s back, where it may get hydrodynamic assistance. The newborn
calves, 1.6 m long, are uniform dark gray; white patches later appear on
the ventral surface and spread with increasing age to the flanks and back.
The
death rate among adults is probably quite low - 7 to 9 % a year - and the
mortality of the young unknown. The late and slow reproductions means that
numbers of narwhals, once reduced, could only increase slowly. |
| The
narwhal inhabits ice covered Arctic seas, and only rarely wandering into
temperate waters. In icier waters, it is more likely to be preyed upon
by killer whales, and would have to compete for food with other species
of whales better adapted to warmer conditions. It has no dorsal fin
in hindering it in swimming under the ice, and can break several centimeters
of ice with its forehead. Narwhals can travel miles under the ice between
breathing opportunities, and can use even the breathing holes made in the
ice by the Arctic seals, seals surfacing head first and then sliding back
underwater. In Canadian waters, narwhals winter in the close pack ice of
baffin Bay and Davis Strait, between Baffin Island and Greenland. As the
ice melts in spring, they migrate northward up the east coast of Baffin
Island. Herds of hundreds, heading north and west round Bylot Island off
the northern end of Baffin Island and crowd at the edges of the fast ice
in Pond Inlet, Lancaster Sound and Jones Sound. |
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As
these ice edges retreat with the onset of summer, narwhals penetrate leads
and cracks into Eclipse Sound, Navy Board Inlet, Admiralty Inlet, and Price
Regent Inlet, and as the ice melts, they tend to stay associated with it.
About 1200 narwhals are also found in summer in in northwest Hudson Bay.
They are probably a separate group wintering in Hudson Strait. Photographic
aerial surveys of the main summering areas have estimated the total number
of inhabiting Canadian waters in summer to be about 20 000. Narwhals summer
in the Thule area of northern West Greenland, and over 4000 have been counted
there. It is not known whether the groups in the different fjords in summer
are always the same, or whether they exchange members on the wintering
grounds.
At
the height of summer, narwhals are found in greatest numbers in the
fjords of northern Baffin Island, moving place from place to in herds of
hundreds, but other groups are also regularly found in Peel Sound between
Somerset Island and Prince of Wales Island, and narwhals have been seen
in summer as far northwest as Lougheed Island. It seems as though, by choosing
particular areas in these restricted waters, they can find shelter from
rough seas (which perhaps, living in pack ice of other times of the
year, they are not accustomed to) or places to stay away from killer whales,
from which at other times of the year the ice offers some protection. When
the days shorten in September, and seas start to freeze, narwhals head
out again into Baffin Bay. Herds are sometimes trapped in the forming ice;
then tens or hundreds may crowd at a single contracting hole in the ice,
where they may become prey for polar bears or Inuit.
The
narwhal is also found in other parts of the Arctic: in the waters of
West Greenland, and in the northern Atlantic. Although not unknown, it
is uncommon in the Bering, Beaufort and Chukchi seas, and in the seas to
the north of Siberia.
Excerpt
from "The Narwhal" by Michael Kingsley, Department of Fisheries and Oceans.
For
pictures of narwhal tusks for sale see: Narwhal
Tusks |
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