Meet the Narwhal

Meet the Narwhal

Ingrid Schoonover

Fall 2020

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Meet the Narwhal

Classification and Taxonomy

Class: Mammalia

Order: Cetacea, but more recently Cetartiodactyla12

Suborder: Odontoceti

Family: Monodontidae

Genus/Species: Monodon monoceros

Common Names: Corpse Whale, Narwhal, Narwhale, Unicorn Whale, Moon Whale, Polar Whale.

Conservation: IUCN Species of Least Concern (2017) & CITES Appendix II.12

Evolutionary History

The Monodontidae fossil record dates to as early as the late Miocene. These extinct monodontids were found in much warmer latitudes24 including off the coast of Peru11, and it was not until the early Pliocene that they began migrating towards the North Atlantic11. Today there are only two living species8,13 in the Monodontidae family: Narwhals (Monodon Monoceros) and Belugas (Delphinapterus leucas)12. These two living species are restricted to Artic waters, they lack dorsal fins8, have broad rounded flippers8, blunt bulbous heads8, and have unique skeletal muscles25 adapted for cold-water swimming and diving.

Anatomy/Morphology

Weight: 3,500 to 4,200 pounds (1600-1900 kg) in males, and 2,000 to 3,400 pounds (900-1550 kg) in females.2,22,27

Length: 16.4 to 17.7 feet (5-5.4 m) in males, and 13.1 to 16.1 feet (4-4.9 m) in females.2,22,27

Appearance:* Adults have black6 and brown speckles throughout the top of their body and a lighter underside10. The head, neck, fluke, and flipper edges are black15. They develop white patches10 with age and seniors can be completely white22.  They have a dorsal ridge22 instead of a dorsal fin22. Males have a 10 f00t (3 m) long18,26 spiraled tusk13 that erupts from the left lip14.

Distribution and Habitat

Map Credit: Lowry et al., IUCN Red List, 2017.

There are approximately 170,00012 Narwhals worldwide in 12 distinct geographic populations12, which can be found between  70°N and 85°N15 in the Arctic waters6,12 around Canada, Greenland, the Russian Federation, Svalbard, and Jan Mayen. The have high site fidelity12 which means that populations follow the same 620-mile (1000 km)9 two-month12,15,22 migration routes between their summer and winter homes. They spend the winter under the deep-sea ice, feeding extensively at depths up to 1-mile (1500 m)12, and they gather near shallow-water coastlines during the summer9.

Behavior

Narwhals are social animals that travel in pods of 5 to 20 individuals14,15, but they migrate in much larger groups and during the winter12 the populations around ice holes can number in the hundreds or thousands14. They are very vocal and use echolocation to communicate with each other and hunt6, some have even speculated that their tusks play some role in echolocation15.  They have frequently been observed swimming upside down4, which can help them maneuver under sea ice and prevent injury to tusks.

Biology/Development

Lifespan: On average 50 years12,16,22 up to 12523.

Development: At birth calves are 5.2 feet (1.6 m) in length23 and weigh 176 pounds (80 kg)23. They are born with a blotchy gray coloration22. Females sexually mature at 6 years23 of age and 11.9 feet6 (3.6m)6, males mature later at 8 years23 and 13.8 feet6 (4.2 m)6 in length.

Reproduction: Breeding occurs12 during the winter3 and spring.6,22 Females give birth to a single calf every three years6 in the spring10 or summer6,20 after a 14 to 16-month gestation6,22 period and calves nurse for up to two years6.

Ecology

Diet: Narwhals feed predominantly during the winter months9,12, diving at a rate of 2 m/s15 to depths of (800-1,500 m)9,15 to hunt for fish5, squid, and shrimp9. Some examples of prey include Greenland halibut12, artic cod12, polar Cod12, capelin1,9, Gonatus fabricii squid1,6, redfish6, wolffish9, and sometimes skate eggs9.

Predators: Narwhals are among the dominant predators of the artic but they are still preyed upon by polar bears1,13, orcas11,15, Inuit people13, walruses14, and the Greenland shark9,11. This is especially true for entrapment events where narwhals become trapped by ice.13,4

Tooth Morphology

Narwhals have two vestigial teeth18 and two canine teeth;18 the left canine 13,14 develops into the “tusk” in males and 15% of females3,28, whereas the right canine usually remains embedded in the jaw28. This tusk is possibly a secondary sex characteristic3,14,26 that serves a purpose in dominance and mate selection. More likely, the tusks which contain 10 million nerve endings3,15,26 are used as sensory organs to detect temperature3, salt concentration3,17,23, and possibly for locating prey21,28.Unerupted teeth in females and juveniles are also connected to the nervous system and thus can serve a sensory function17.

Photo Credit: (Nweeia et al., 2012).

References

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