Form and Function
Narwhals are well adapted to the arctic marine environment in
which they live. Narwhals have a streamline body with two dorsal
flippers and lack a dorsal fin. Propulsion comes from their
tail. They have a thick layer of blubber to protect their bodies
from the cold (Williams et al. 2011).
Their bodies are specially adapted for deep dives. Narwhals have a
compressible rib cage that s
upports their organs in deep water where
pressures are extreme (Heide-Jorgensen & Garde 2011). Two other
keys to the narwhal’s remarkable diving ability can be found in
their muscles. First, narwhal muscles fibers contain twice the
amount of myoglobin of other oceanic mammals, which allows their
muscles to work longer (Williams et al. 2011). The composition of
the narwhal muscle also assists them on long, deep dives. Narwhal
muscle is made of primarily slow-twitch muscle fibers. These muscles
fibers use oxygen more efficiently and are used for endurance
instead of speed (Williams et al. 2011). These adaptations allow
narwhals to go 25 minutes between breaths and to record some of the
deepest dives ever recorded for a mammal at 1800m deep, which is
greater than one mile (Williams et al. 2011).
The scientific name for narwhal, Monodon monoceros, means
“one tooth”, “one horn” (Heide-Jorgensen & Garde 2011). This name
refers to the narwhal’s most recognizable feature, the tusk. Unlike
other toothed whales, narwhals only have two teeth. These two teeth
are both in the upper jaw. In males, the right tooth usually remains
small and does not grow out of the mouth, while the left tooth grows
into a tusk that can be 3 meters long (Curry 2010). A small
percentage of males have two tusks, in which both teeth have grown
into tusks, known as "bidental" narwhals. The tusks are spiraled
with a counter clockwise
rotation, relative to the narwhal (Curry 2010).
Ordinarily, females lack tusks. The purpose and function of
their tusks has been widely speculated. Originally, it was believed
that the tusks helped them hunt for food, or break breathing holes
in the ice (Curry 2010). Today, researchers believe that the tusks
are important in sexual selection. For example, the narwhal with the
largest tusk would have the right to mate first (Curry 2010). Other
researchers believe that the tusk is also filled with neurons and
sensory cells that help the narwhal determine the conditions of its environment
(Curry 2010; Williams et al. 2011). This would be advantageous to
the narwhal during deep dives where there is no light and hunting
would be primarily done by touch (Laidre 2004).