They create a direct link from the narwhal nervous system to the outside world. In the teeth of other animals, the tubules abruptly end in the layer before the outermost enamel covering.
To figure out why the narwhal evolved such a unique sensory tool, scientists turn to clues from the environment. Some researchers believe tusks might help the whales survive the harsh and ever-changing conditions in the Arctic.
Freezing temperatures and shifting ice floes can occur unexpectedly, covering the few breathing holes narwhals rely on to survive. When the weather shifts quickly, narwhals can die from exhaustion and starvation.
In , the largest entrapment on record killed more than 1, narwhals at once. Living in such a hazardous place, it would be highly beneficial for narwhals to have a way of predicting when ice shifts will occur. One study found that the sensory capabilities of the tusk may be strong enough to detect changes in the ocean salt concentration. Ocean saltiness is related to sea ice cover —as ocean water freezes salt gets left behind in the surrounding water.
Perhaps a narwhal uses its tusk to check the weather forecast and then steer clear of the colder and saltier water. Scientists are still puzzled by the discovery of the unique tusk anatomy. Scientists only just discovered the sensory capabilities in , so for now, we can only speculate. Perhaps the tusk is used to locate females in heat by pinpointing hormones levels in the water.
Or, perhaps, the sensory capability is a newly evolved trait that emerged after the tusk became a male-only trait. A recent drone video shows a group of particularly handy narwhals using their tusks to stun fish with a quick strike before eating them. The discovery was quite a surprise to scientists who were using the drones to estimate current narwhal populations. More research is needed to tease out how this discovery fits in with the larger picture of tusk evolution.
In fact, the tusk might be used in multiple ways involving both natural and sexual selection, as is the case for African elephants. Adult male narwhals grow to be about 15 feet 4. The tusk — which is a long, straight tooth — grows up to 9 feet long 3 m out of the male's mouth, according to the Polar Science Center at the University of Washington.
Although narwhals are considered toothed whales, their mouths don't contain any functioning teeth. In males, the right canine tooth remains in the skull and never grows out, while the left canine is the one that shoots out through the gums in a counterclockwise, spiral pattern to form the tusk. Rarely, both teeth protrude, giving the narwhal two tusks. Females are much smaller than males, growing to be about 13 feet 4 m long and weighing about 2, lbs.
Experts have long speculated about why narwhals have this bizarre, elongated tooth. Some theories suggest that the tusk is a tool for survival, as the whales could possibly use it to break up ice at the surface, spear fish for dinner or dig for meals in the seafloor. But the vast majority of female narwhals don't have tusks, and females tend to live longer than males.
Therefore, experts think the tusk is probably not an advantage for survival but rather a primarily male sex characteristic that serves as a formidable weapon for competing with other males for mates. But the tusk may also have another purpose. A study published in the journal The Anatomical Record found that the narwhal's mysterious tusk is full of sensitive nerve endings that allow the whale to detect changes in the environment, such as fluctuations in temperature and salinity.
These findings suggest that the tusk might also be a sensory organ. As for the rest of the narwhal body, their heads are relatively small and round compared with those of other cetaceans.
Narwhals' fins are also short and round, and they have a short ridge along their back in place of a dorsal fin. Their tail fluke is also convex, rather than concave as with other cetaceans. They can be found in the coastal areas during the summer and farther out at sea during the winter.
Narwhals are the deepest divers in their family and can swim to depths of at least 4, feet 1, m , where no light can reach and water pressure exceeds 2, psi atmospheres , according to NOAA. These skilled divers stay under the water for about 25 minutes per dive, on average.
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Closest relatives The Narwhal is most closely related to the beluga. A tusk or a tooth? Diet Narwhals feed mainly on Greenland halibut, Arctic and polar cod, squid and shrimp. Changing colours Narwhals change colour with age. Great divers Narwhals commonly dive to metres, though they can dive in excess of 1, metres for more than a 25 minute period. They are pretty big They can weigh up to 1. Affected by climate change Like polar bears , narwhals depend on sea ice and are directly impacted by rapid climate change —studies have shown that they are one of the species most vulnerable to the ecological effects of climate change because of increased predation by killer whales, changes to their prey base, and likely increased risks of entrapment in unpredictable ice conditions.
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