Tuesday, 28 December 2010

Narwhal: Unicorns of the Sea

Image showing four narwhals tusking
Male Narwhals
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Monodontidae
Genus: Monodon
Species: Monodon monoceros
Conservation Status: Near Threatened
Common Name(s): Narwhal

The Narwhal, or the unicorn of the sea as it is sometimes called, is a medium-sized toothed whale and one of the two surviving representatives of the family Monodontidae. The other member is the beluga whale (Delphinapterus leucas).

As you can see on the article's images and videos, these magnificent creatures are easily distringuished by the long straight tusks that males have.

Distribution
Narwhals occur predominantly in the Atlantic and Russian areas of the Arctic Ocean. They are commonly sighted in the northern part of Hudson Bay, Hudson Strait, Baffin Bay; off the east coast of Greenland and in a strip running east from the northern end of Greenland round to eastern Russia (170° East). Lands falling under this strip include Svalbard, Franz Joseph Land, and Severnaya Zemlya. The northernmost recordings come from the north of Franz Joseph Land, at about 85° North latitude. Most individuals are concentrated in the fjords and inlets of Northern Canada and western Greenland.

Narwhals can reach depths of 1,500 m (~4921 ft).


Map showing the distribution of Narwhals
Frequent (solid blue) and rare (striped blue) sightings of narwhals

Description
Narwhals are medium-sized whales, with a body length ranging from 3.3 to 5.5 m (~13 to 18 ft). Generally, males are slightly larger and heavier than females. Males have an average length of 4.1 m (~13.5 ft 5) and females an average length of 3.5 m (~11.4829 ft). Males have an average weight of 1,600 kg (~3,527 pounds) whereas females have an average weight of 1,000 kg (~2.204 lb).

Adults have a bluish-gray cylindrical body with white blotches. Newborns are darkest when born, becoming whiter and whiter as they age. Old males are almost entirely white.

Size comparison between a human and a narwhal
Narwhal size compared to an average human

The species has no dorsal fin, most probably an evolutionary adaptation that allows it to swim under the ice with greater ease. The neck vertebrae are jointed, instead of being fused like in most whales. Both these traits are shared by the closely related beluga whale.

The head is round, featuring a small mouth and a blunt snout. The narwhal’s compact body shape along with the thick layer of blubber (fat) helps the species to retain heat in the icy Arctic waters it inhabits.

Males reach sexual maturity at 11 to 13 years of age, when they are about 3.9 m (~13 ft) long, whereas females attain sexual maturity when they are 5 to 8 years old, at a length of about 3.4 m (~11 ft). Narwhals have a maximum lifespan of 50 years.


Tusks and Their Purpose
The long hollow tusk that males have is surely the most unique and distinctive trait of these strange animals. Each tusk is essentially an enlarged, canine tooth that protrudes from the left side of the upper jaw, through the lip, forming a left-handed helix spiral. The right incisor typically stays small. The tusk grows throughout the narwhal's entire life, commonly reaching lengths of 1.5 to 3.1 m (~5 -10 ft).

Interestingly, in about one in every 500 males, the right canine grows as well and the male gets to have two tusks! In rare occasions, females also have a tusk, which however is shorter and less-spiraled. It's possible for females to have two tusks as well, although this is extremely rare. Actually, there has been only one recorded dual-tusked female as of 2014.

One tusk skull vs two tusk skull (narwhal)
Normal narwhal skull with one tusk (left)
Narwhal skull with two tusks

The exact purpose(s) of the tusks has yet to be unveiled, although there are some good theories on the table. In most mammals, horns, tusks and other similar structures are a secondary sexual characteristic used by males to attract females (like a sign of manliness) and to assert dominance among other male competitors. Asserting dominance is probably excluded in this case, as males rarely use them for fighting or other aggressive behaviors. However, they may help determine social rank, maintain dominance hierarchies, or help young males develop skills necessary for performance in adult sexual roles.

In the past, it was hypothesized that tusks are used for breaking the ice. But similarly to fighting, this occurs very rarely.

Recent research has shown that the tusk is an innervated sensory organ with millions of patent nerve endings connecting the external ocean waters with the brain. We still don't know what kind of information narwhals get through their tusks. One assumption is that they can sense changes in water temperature, pressure, and salinity gradients.


Great narwhal footage by National Geographic

Diving
Narwhals are capable of really deep dives, amongst the deepest compared to other marine mammals, like whales and dolphins. They routinely go 800 meters (~2,625 ft) deep, 15 or more times per day. Occasionally, they will go even deeper, reaching depths of at least 1,500 meters (~4,921 feet). These deep dives last for about 25 minutes each, including the time spent at the bottom and the transit down and back from the surface.

Diet
These specialized Arctic predators have a relatively restricted diet, primarily based on Greenland halibut (Reinhardtius hippoglossoides), Arctic cod (Boreogadus saida), cuttlefish, shrimps and armhook squid. Other prey researchers have found in their stomachs include:
  • Wolffish 
  • Capelin 
  • Skate eggs 
Rocks have also been observed, probably accidentally ingested when feeding near the bottom.

Short clip about the tusks of Narwhals


Predators
Humans excluded, narwhals have very few natural enemies, with predation accounting for a relatively small number of deaths. Polar bears sometimes swipe young narwhals out of breathing holes whereas orcas can group together to hunt and kill a single narwhal. Additionally, Greenland sharks and walruses prey occasionally on juveniles and wounded or ill adults.

When it comes to escaping aquatic predators like killer-whales, narwhals prefer to use their prolonged submergence to hide under the ice rather than relying on their speed.

Behavior & Communication
Narwhals tend to stay in groups comprised of five to ten individuals. During the summer, many such groups come together and form even larger aggregations, ranging from 500 to over 1000 narwhals. Male narwhals are known to rub each other's tusks every now and then. This activity is called tusking and possibly functions as a means of maintaining social dominance hierarchies.

Like most toothed whales, the species uses sound to communicate, navigate and hunt for food, including "clicks", "whistles" and "knocks". Other sounds include trumpeting and squeaking door-like sounds.

Reproduction
Very little is known about the reproductive patterns of the species.This is because breeding takes place in remote and hard to reach areas. Adult narwhals mate from March to May.

Gestation lasts 14 months. Each female gives birth to a single young. The calves are born between June and August. They are dark grey, have no white spots and have an average length of 1.5 meters (~5 ft). They weigh about 80 kg (~176 pounds).

Newborns begin their lives with a thin layer of blubber that thickens as they nurse their mother's full-of-fat milk. Lactation lasts for about 20 months. During this period, they learn all the skills necessary for survival. Mothers and youngs stay close while travelling.

Conservation status and threats
Today narwhals are listed by the IUCN as "Near Threatened", with their total population estimated to be about 75,000 individuals, with a declining trend. They are primarily threatened by human-related activities. In short, the three major threats are hunting, climate change, and industrial activities.
The IUCN notes:
"Narwhal populations are potentially threatened by hunting, climate change, and industrial activities. Narwhals were never the targets of large-scale commercial hunting except for a brief period of perhaps several decades of the early 20th century in the eastern Canadian Arctic (Mitchell and Reeves 1981). They were hunted opportunistically by commercial whalers, explorers and adventurers in many areas. For many centuries, narwhals have been hunted by the Inuit for human food, dog food and tusk ivory (Born et al. 1994). The mattak (skin and adhering blubber) is highly prized as food and provides a strong incentive for the hunt (Reeves 1993), but in recent years the cash value of ivory and the need for cash to buy snowmobiles have both greatly increased. Potential future threats include habitat degradation from oil exploration and development (e.g., in West Greenland) and increased shipping in the high Arctic (NW and NE passages), all of which is bound to increase with the dramatic, ongoing reduction in sea ice. 
In West Greenland, catches have declined since 1993 with no significant sex bias. Heide-Jorgensen (2002) estimated the annual catch rate at 550 between 1993 and 1995. In 2004, the estimated catch in West Greenland was 294 (NAMMCO/JCNB 2005), including whales that were struck and lost. In contrast to West Greenland, there has been an 8% increase in catches in East Greenland since 1993 (NAMMCO/JCNB 2005).
The narwhal is actively hunted only in Canada and Greenland. In the eastern Canadian Arctic, the average reported landed catch per year from selected communities was 373 between 1996 and 2004 (NAMMCO/JCNB 2005). In Canada the majority of the communities take a greater proportion of males than females throughout the seasons. Annual catch statistics in Canada substantially underestimate the total numbers of Narwhals killed due primarily to the incomplete reporting of whales that are struck and killed but lost (IWC 2000; NAMMCO/JCNB 2005; Nicklen 2007).

Narwhals supplied various staples in the traditional subsistence economy. Today the main products are mattak and ivory (Reeves 1993, Reeves and Heide-Jørgensen 1994, Heide-Jørgensen 1994, Nicklen 2007). Narwhal tusks from Canada and Greenland are sold in specialty souvenir markets domestically and also have been exported. However, in Greenland, the export of tusks is currently banned. In Canada, the quota system that had been in place since the 1970s was replaced by a community-based management system implemented in the late 1990s and early 2000s (COSEWIC 2004). The hunt is managed by local hunter and trapper organizations with harvest limits established in some communities. Compliance has been questionable (COSEWIC 2004). Under this system, removals from some summering aggregations are probably sustainable, however, there is concern that removals from other summering aggregations may not be (NAMMCO/JCNB 2005). In Greenland, a quota system was introduced in 2004 by the Greenland Ministry of Fisheries and Wildlife. The quota was set at 300 Narwhals (of which 294 were taken), divided among municipalities of West Greenland. Compliance reportedly has been good (NAMMCO/JCNB 2005) although there is concern that catch limits may be set too high (IWC 2007, p. 52).

The effects of climate change on Narwhals are uncertain. Narwhals are well adapted to a life in the pack ice as indicated by the fact that there is very little open water in their winter habitat (Laidre and Heide-Jørgensen 2005b). They spend much of their time in heavy ice and are vulnerable to ice entrapments where hundreds can become trapped in a small opening in the sea ice (savssat) and die. This occurs when sudden changes in weather conditions (such as shifts in wind or quick drops in temperature) freeze shut leads and cracks they were using. When entrapped whales are discovered by hunters, they normally are killed. A recent assessment of the sensitivity of all Arctic marine mammals to climate change ranked the narwhal as one of the three most sensitive species, primarily due to its narrow geographic distribution, specialized feeding and habitat choice, and high site fidelity."

A male narwhal is captured and satellite tagged
Photo of a male narwhal as it is captured and satellite tagged.

In captivity
Some animals are not meant to be caged and the Narwhal is one of them. Many attempts to keep the species in captivity were made in the past, all unsuccessful. All captive individuals die in a matter of days or months, for unknown reasons.

In 1969, an orphaned calf was caught in the Grise fjord in Canada. The calf was airlifted to the New York aquarium and died after a month. A year later, the Vancouver Aquarium captured 6 narwhals, all again died within a few months.

Narwhal and the myth of unicorns
According to modern historians, many medieval Europeans believed that narwhal tusks were horns removed from the legendary unicorn. Back then, unicorn horns were believed to have magical powers, such as neutralizing poison and curing melancholia. As a result, Vikings and other northern traders made quite a lot of money, routinely selling tusks for many times their weight in gold!

It wasn't until the Age of Exploration that the true origin of these tusks begun to unfold, as explorers and naturalists began to visit the Arctic regions.

Other Interesting Facts About Narwhals
- The word narwhal is believed to derive from old Norse for "corpse whale," probably due to the species' mottled, splotchy coloring, reminiscent of the grayish, blotched color of drowned sailors. The species' scientific name, Monodon monoceros, is derived from Greek and roughly translates to "One-tooth, One-horn".
- A high number of narwhals die every year due to suffocation, typically after they fail to leave before the surface of the Arctic waters freezes Open water is formed in ice-covered water by fracturing events induced by strong winds, but when these conditions are absent ice can quickly form. The events can trap groups comprised of up to 600 individuals! Most entrapment events occur in narwhal wintering areas like the Disko Bay. The largest entrapment event occurred in 1915 in West Greenland. In this event, more than 1,000 narwhals got trapped and died under the ice!

References & Further Reading-
- Nweeia MT, Eichmiller FC, Hauschka PV, Tyler E, Mead JG, Potter CW, Angnatsiak DP, Richard PR, Orr JR, & Black SR (2012). Vestigial tooth anatomy and tusk nomenclature for monodon monoceros. Anatomical record (Hoboken, N.J. : 2007), 295 (6), 1006-16 PMID: 22467529
- Nweeia MT, Eichmiller FC, Hauschka PV, Donahue GA, Orr JR, Ferguson SH, Watt CA, Mead JG, Potter CW, Dietz R, Giuseppetti AA, Black SR, Trachtenberg AJ, & Kuo WP (2014). Sensory ability in the narwhal tooth organ system. Anatomical record (Hoboken, N.J. : 2007), 297 (4), 599-617 PMID: 24639076
- Heide-Jørgensen, M., & Acquarone, M. (2014). Size and trends of the bowhead whale, beluga and narwhal stocks wintering off West Greenland NAMMCO Scientific Publications, 4 DOI: 10.7557/3.2844
- Laidre, K., & Heide-Jorgensen, M. (2005). Winter feeding intensity of narwhals Marine Mammal Science, 21 (1), 45-57 DOI: 10.1111/j.1748-7692.2005.tb01207.x
- Finley, K., & Gibb, E. (1982). Summer diet of the narwhal (Monodon monoceros) in Pond Inlet, northern Baffin Island Canadian Journal of Zoology, 60 (12), 3353-3363 DOI: 10.1139/z82-424
- Laidre, K., Heide-Jørgensen, M., Dietz, R., Hobbs, R., & Jørgensen, O. (2003). Deep-diving by narwhals Monodon monoceros: differences in foraging behavior between wintering areas? Marine Ecology Progress Series, 261, 269-281 DOI: 10.3354/meps261269
Watkins, W. (1971). Underwater Sounds of Monodon (Narwhal) The Journal of the Acoustical Society of America, 49 (2B) DOI: 10.1121/1.1912391
- Williams, Terrie M.; Noren, Shawn R.; Glenn, Mike (2011). Extreme physiological adaptations as predictors of climate-change sensitivity in the narwhal, Mondon monceros Marine Mammal Science : 10.1111/j.1748-7692.2010.00408.x
- Laidre, K., Heide-Jørgensen, M., Stern, H., & Richard, P. (2011). Unusual narwhal sea ice entrapments and delayed autumn freeze-up trends Polar Biology, 35 (1), 149-154 DOI: 10.1007/s00300-011-1036-8
- Heide-Jørgensen, M., Hansen, R., Westdal, K., Reeves, R., & Mosbech, A. (2013). Narwhals and seismic exploration: Is seismic noise increasing the risk of ice entrapments? Biological Conservation, 158, 50-54 DOI: 10.1016/j.biocon.2012.08.005
- Watt, C., Heide-Jørgensen, M., & Ferguson, S. (2013). How adaptable are narwhal? A comparison of foraging patterns among the world's three narwhal populations Ecosphere, 4 (6) DOI: 10.1890/ES13-00137.1
- Laidre, K., & Heide-Jørgensen, M. (2005). Arctic sea ice trends and narwhal vulnerability Biological Conservation, 121 (4), 509-517 DOI: 10.1016/j.biocon.2004.06.003
- Jefferson, T.A., Karczmarski, L., Laidre, K., O'Corry-Crowe, G., Reeves, R.R., Rojas-Bracho, L., Secchi, E.R., Slooten, E., Smith, B.D., Wang, J.Y. & Zhou, K. (2008). Monodon monoceros. IUCN Red List of Threatened Species. 

6 comments:

  1. best animal in the world

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  2. I used to think they were mythical creatures and that they didn't exist. people should be more aware of there awesomeness

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  3. narwhals are so legitiment i love them so much

    narwhals narwhals swimmin in the ocean causin a cmotion cuz they are so awesome narwhal narwhals swimmin in the ocean pretty big and pretty white theyd beat a polar bear in a fight

    animal taken by Kristin F

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  4. These animals are like unicorns that live in the ocean but are like whales

    ReplyDelete
  5. Magical unicor of the sea!

    ReplyDelete