Whales of a tusk swim together.

Paul Nicklen/National Geographic/Getty Images

Narwhal Behavior

Narwhals, like other toothed whales, have big brains in relation to their body size. In fact, the size of an odontocete's brain is second only to yours [source: National Science Foundation]. Toothed whales such as the narwhal display humanlike behavior we associate only with apes, like recognizing themselves in the mirror and understanding abstract ideas [source: National Science Foundation]. The narwhal is one smart cookie.

Interestingly, the first big jump in whale brain size seems to have happened when cetaceans first started using echolocation, the ability to locate objects with sound. The narwhal swims through deep waters in search of its prey, and as you might imagine, it's a bit murky down there. Bats, who hunt at night, use echolocation to find their prey, too.

First, the whale has to produce a sound. Toothed whales don't have anything exactly like our vocal cords, although they have similar structures. It's thought that they produce their sounds in their nasal passages [source: Hebridean Whale and Dolphin Trust]. The melon, the fatty structure we mentioned before, then focuses these sounds into a beam before sending them out. The sound waves then travel until they hit something, at which point the echoes bounce back to the whale. The whale receives these echoes either in the lower jaw or directly in the skull, depending on the frequency of the sound [source: Hebridean Whale and Dolphin Trust]. Each species has a different range of frequencies, depending on what they need echolocation for -- low-frequency sounds go farther, while high-frequency sounds are suited to short distances. From the echoes, the whales can determine where their food is, among other things.

How low can you go? A mile, actually.

Paul Nicklen/National Geographic/Getty Images

Odontocetes don't make whale songs -- you've probably heard a dolphin's clicks and whistles before. Narwhals whistle and produce a combined pulsed/tonal sound [source: ScienceDaily]. Researchers think the narwhals use echolocation to communicate as well as hunt.

The diving patterns of narwhals aren't completely understood. They're recognized as one of the deepest-diving cetaceans, descending more than a mile (1.6 km) into the ocean, but a mile isn't the norm. A study recorded one narwhal making regular deep dives, with long breaks at the surface, while the other subject made lots of shallow dives with less time at the surface [source: Laidre]. The same study, conducted in Tremblay Sound and Creswell Bay, reported a dive pattern: a steep descent with a short stop at the bottom, then a slower ascent to the surface [source: Laidre]. But diving behavior depends on what time of year it is and therefore the whale's location due to migration -- during the winter in a place like Baffin Bay, the narwhals dive deeper and longer in search of polar cod and other fish that don't like to hang out near the surface. In the summer when narwhals migrate to a more hospitable clime, it's not necessary to go so deep.

And now let's look at the narwhal's distinguishing feature: its tusk.