Narwhal

Monodon monoceros (Linnaeus, 1756)

English: Narwhal
German: Narwal
Spanish: Narval
French: Narval

Drawing of M. monoceros © Würtz-Artescienza

1. Description
Adult narwhals are completely mottled on the dorsum with increasingly white fields on the ventral side. Old males only maintain a narrow dark spotted pattern on the top of the back, whereas the rest of the body is white. As opposed to other cetaceans, the tail fluke is concave and the dorsal fin is replaced by a low ridge. In males, the left of two elongated maxillary teeth grows and protrudes through the maxillary bones and skin of the rostrum. During growth, the tusk spirals and grooves to the left. Females may sometimes attain a tusk as well, some males may lack even one whereas others may have two tusks. The largest tusk measured 267 cm, normal size is 200 cm. The tusk is believed to be a secondary sexual character determining social rank among males. Body length is 400 and 475 cm for adult males and females, respectively, and mass reaches 100 kg in females and 1600 kg in males (Heide Jorgensen, 2002).

According to Hay and Mansfield (1989) the narwhal has at present a discontinuous circumpolar range, since it is not abundant in the central Canadian Arctic and is rarely found in the western Canadian Arctic and in Alaskan and Siberian waters. According to Born (1994) it is unlikely that narwhals from the eastern Canadian Arctic have intensive contact with animals from eastern Greenland.

Palsboll et al. (1997) determined the nucleotide sequence of the first 287 base pairs in the mitochondrial control region from 74 narwhals collected in the North-West Atlantic. Their results suggest a recent expansion in abundance from a small founding population. Despite the low degree of variation, frequencies of the common haplotypes differed markedly between areas. This indicates isolation, even between geographically close areas, as well as fidelity to specific summer and autumn feeding grounds.

2. Distribution
The narwhal is discontinuously circumpolar and arctic. It is observed very infrequently south of 65°N in Greenland. However, during spring, when distributional ranges may overlap north of Greenland, its range may become circumpolar (Born, 1994). The main part of the population occurs in the eastern Canadian Arctic and west Greenland. Observations by Gjertz (1991) suggest that on Svalbard narwhals concentrate in the north-west area of Spitzbergen.

In the eastern Canadian Arctic the range extends from Lancaster Sound, and Kane Basin, south through Baffin Bay and Davis Strait as far as Cumberland Sound on Baffin Island and Disko off western Greenland; A possibly isolated population lives in Foxe Basin and northern Hudson Bay. Along the east coast of Greenland it ranges from Nordostrundingen (81°N) south to Umiivik (64°N), thence eastwards in the high arctic pack ice through the Greenland, Barents, Kara, Laptev and East Siberian Seas to about 165°E, and from about 85°N southward to Svalbard, Zemlya Frantsa Iosifa, Novaya Zemlya, Severnaya Zemlya, Novosibirskiye Ostrova, and Ostrova De-Longa (157°E) (Rice, 1998).

Narwhals are vagrant south to the coast of Labrador (Rice, 1998), rare to accidental south to Iceland, the Norwegian Sea, the North Sea (south to the British Isles, The Netherlands and Germany), the White Sea, and the arctic coast of mainland Eurasia, and east into the Chukchi Sea and the Bering Sea, as far south as Komandorskiye Ostrova and the north side of the Alaska peninsula (Rice, 1998).

Narwhal distribution (mod. From Heide-Jorgensen, 2002; ; ©CMS / GROMS).

3. Population size
According to IWC (2000), Hay and Mansfield (1989) and Strong (1988), the most recent population surveys were carried out in 1984 and yielded 18,000 narwhals in the four major summering areas south of Lancaster Sound (Eclipse Sound, Admiralty Inlet, Prince Regent Inlet and Peel Sound). A further 1,000 narwhals were estimated for the Repulse Bay - Frozen Strait area. Koski and Davis (cited in Born, 1994) recorded 34,000 narwhals in parts of Baffin Bay after the end of winter.

Hay and Mansfield (1989) suggest from unpublished data, that in 1971 the Thule-district narwhal population in north-west Greenland was estimated ranging between 1,500 - 2,500. A more recent land-based count in 1984 (Born, 1994) showed the population in Inglefield Bay to number at least 4,000.

In the Eurasian sector of the arctic the only known estimate of narwhal numbers is from Scoreby Sound and Kung Oscar Fjord in eastern Greenland. A conservative figure of only 176 was obtained from an aerial line-transect survey carried out in September 1983 by F. Larsen (cited in Hay and Mansfield, 1989). Born (1994) confirms that more detailed data is lacking. He suggests that in this sector, narwhals prefer areas distant from the coast and may number at most a few thousand individuals.

4. Biology and Behaviour

Narwhal and kayak © Don McMichael
Habitat: Narwhals are considered deep-water cetaceans, associated with the pack ice (Hay and Mansfield, 1989). Other investigators, however, dispute their characterization as deep-water species, noting that they occur in waters of different depths. Born (1994) suggests that the occurrence of narwhals and belugas is mutually exclusive, since summering and wintering grounds differ both in location and time, which seems to exclude competition for food. When both species do occur in the same areas, they seem to reduce competition by foraging at different depths.

Schooling: Most pods consist of 2-10 individuals but they may aggregate to form larger herds of hundreds or even thousands of individuals (Jefferson et al. 1993). According to Hay (1985) segregation by age and sex within this population is evident, with summering groups consisting of mature females with calves, immature and maturing males, and large mature males.

Reproduction: The gestation period is estimated to be 15.3 months. The season of conceptions is March to May and calving occurs during July and August. Since the lactation period exceeds 12 months, the interval between successive conceptions is usually three years, but about 20% of females conceive at the first breeding season following birth of their calves. The annual population birth rate is calculated to be about 0.07. The basic life history features of the narwhal are similar to those of other medium-sized toothed whales (Hay, 1985).

Food: Prey items include Arctic cod (Boreogadus saida) and polar cod (Arctogadus glacialis), pelagic species associated with ice undersides. Demersal species found at great depths such as Greenland halibut (Reinhardtius hippoglossoides) and bottom-dwelling cephalopods are also taken (Heide-Jorgensen, 2002). Further prey items include squid (Gonatus fabricii), and the shrimps Pasiphaea tarda and Hymenodora glacialis. Narwhals feed heavily during migrations, but very little during the open water season (Hay and MansfIeld, 1989; Reyes, 1991 and refs. therein). Stomach content analyses suggest that these cetaceans feed over a wide range of depths, at least in the Baffin Bay area (Hay and Mansfield, 1989). The deepest recorded diving depth was 1164 m, and dive times usually amount to 20-25 min (Heide-Jorgensen, 2002).

5. Migration
Throughout the whole year, narwhals live in close contact to the arctic pack ice (Born, 1994). They follow the distribution of the ice and move towards coastal areas when these are ice free. During freeze-up, the coastal areas are abandoned and the narwhals move offshore (Heide-Jorgensen, 2002). Observations from airplanes suggest that narwhals overwinter in small groups within heavy pack ice, whereas only a few animals were observed in lose pack ice and open water (Koski and Davis, cited in Born, 1994).

In the Eurasian sector of the Arctic, narwhals probably overwinter in the Greenland Sea and the Barents Sea, althouh Gray (1931, cited in Hay and Mansfield, 1989) suggested Denmark Strait as the wintering area for this population.

Turl (1987) and McLaren and Davis (cited in Hay and Mansfield, 1989) suggest that most of the population of the eastern Canadian Arctic overwinters in both open and closed pack-ice in Davis Strait, especially in the area west and south west of of Disko Island.

The regular occurrence of narwhals at Repulse Bay in north-western Hudson Strait suggests that they may overwinter there as well, or possibly in Hudson Strait where they were also observed by McLaren and Davis (Hay and Mansfield, 1989).

Narwhals display a pronounced annual migratory cycle. Hay and Mansfield (1989) summarise that after spending the winter in Davis Strait, they move northward through the pack ice, congregating in larger groups in May and June at the edge of the fast ice in the fjords of northern Baffin Island and north-western Greenland. A spectacular westward migration of several thousand narwhals through Lancaster Sound was observed by Tuck and by Greendale and Brousseau-Greendale (cited in Hay and Mansfield,1989). These narwhals migrate to the fjords of northern Baffin Island, Prince Regent Inlet, Barrow Strait, and Peel Sound.

After fast ice breaks up and disperses during late June and July, narwhals enter the fjords of northern Baffin Island and north-western Greenland in thousands. They remain there in August and September, sometimes in the bays at the heads of the fjords. Prior to the formation of new ice in October, narwhals leave the fjords and migrate southwards, appearing sporadically at locations on the east coast of Baffin Island and the west coast of Greenland. They spend the winter in the pack-ice of Davis Strait, west and south-west of Disko Island.

Recent satellite data confirm these findings. Satellite transmitters were mounted on 3 female and one male narwhal in the Melville Bay August 1994 (Anonymous, 1997). The females stayed in Melville Bay until the transmitters stopped transmission in September. The male left Melville Bay mid-October and, like the animals tagged in 1993, it headed toward deep water in Baffin Bay where it frequently divided down to 1000 metres. In the beginning of December it was located approximately 200 km west of Disko Island.

Heide-Jorgensen and Dietz (1995) collected dive data from nine narwhals instrumented with satellite-linked dive recorders in Northwest Greenland in August-September 1993 and 1994. Data were collected for periods ranging from a few weeks to 9 months. The narwhals made daily dives to depths of more than 500 m and frequently dived to 1000 m or more. However, most of the time spent below the surface was in the water column at depths of between 8 and 52 m.

At summering grounds in West Greenland and Canada, narwhals moved back and forth between glacier fronts, offshore areas and neighbouring fjords (Dietz et al. 2001). When fast ice formed, the whales moved out to deeper water, usually up to 1000 m water depth. In October, the whales moved southward toward the edge of the continental shelf where water depth increases over a short distance from 1000 to 2000 m. This slope in central Baffin Bay was also used as a wintering ground, and even though the whales seemed stationary in this area, they still conducted shorter movements along the steep continental slope. Narwhals satellite-tracked from Canada and West Greenland were within a few kilometres from each other at these wintering grounds. The importance of this witering ground in central Baffin Bay has also been confirmed by aerial surveys (Heide-Jorgensen, 2002).

The migratory cycle in east Greenland waters is not well known. Apparently narwhals migrate to the north and north-east into the ice fields of the Greenland Sea during May-July. Some whales migrate eastwards to the vicinity of Franz Josef Land and as far east as the new Siberian Islands. A few whales also visit the fjords of north-western Greenland. Their southward migrations in autumn lead them to the southern Greenland Sea, Barents Sea and Danmark Strait (Hay and Mansfield, 1989).

6. Threats

Drawing of M. monoceros by courtesy of North West Territories PAS

Direct catch: The narwhal has been hunted since the earliest times by the Inuit (Reyes, 1991). According to this source, the annual hunting mortality may be in the order of 1,000 animals to day. Heide-Jorgensen (2002) estimates annual catch rates at 550 and 280 between 1993 -1995 in Greenland and Canada, respectively. According to Reeves (1992) Inuit in Canada kill several hundred narwhals in most years. While male narwhal composed most of the landed catch, annual harvest statistics underestimated the total numbers of narwhal killed due primarily to the non-reporting of struck and killed but lost whales. The estimated total kill of narwhal exceeded the reported landed catch by 40% (Roberge and Dunn, 1990). Narwhals supplied various staples in the traditional subsistence economy. Today the main products are muktaaq and ivory. The large tusks of adult males are sold in the speciality souvenir market both inside Canada and in the global marketplace. The price of narwhal ivory has increased substantially over the past 25 yr, with steep increases in 1967, 1972, and the late 1970s to early 1980s. Canadian narwhal ivory traditionally was exported to the United Kingdom, then often re-exported. The EEC ban closed the direct link with the United Kingdom. Consequently, new markets developed in Japan and Switzerland. Narwhal hunting remains an important source of food and cash income for residents of some coastal communities in the eastern Canadian Arctic and Greenland. The international ivory trade provides an incentive to procure large tusks, and this may strongly influence the nature and intensity of the hunt (Reeves, 1992).

Natural enemies: Natural enemies include Greenland sharks (Somniosus microcephalus), orcas, polar bears and walrus, although the mortality rates inflicted by these species do not seem to be very high (Born, 1994). The same author reports that narwhals do occasionally become trapped in fast forming ice and may die during the winter because of exhaustion in an attempt to keep the breathing hole open.

Habitat degradation: Because of their prevalence for high-density pack-ice, narwhals are susceptible to man-made as well as natural climatic changes influencing the water currents and ice formation in the Arctic (Heide-Jorgensen, 2002).

Pollution: Anthropogenic threats include pollution via heavy metals and organochlorines. Cadmium concentrations seem to be significantly higher in narwhals than in other cetaceans (Born, 1994 and references therein). Highest Cadmium concentrations were reported from narwhals living along the Canadian coast, whereas lead concentrations were higher in west Greenland animals. According to Muir et al. (1992) narwhals had 1.4-to 8.6-fold higher ratios of tetra- and pentachlorobiphenyls to PCB-153 (2,2′,4,4′,5,5′-hexachlorobiphenyl), lower 4,4′-DDE/ total DDT ratios and lower proportions of trans-nonachlor to total chlordane components than reported for odontocetes living in more contaminated environments. Mean total PCB concentrations in narwhal were 6- to 15-fold lower than in dolphins from the Canadian east coast and belugas from the St Lawrence River estuary, respectively, while PCC levels were from 4- to about 2-fold lower, and total HCH, dieldrin and total CBs differed by <2-fold. Organochlorine concentrations seem to suggest that narwhals are more exposed to volatile components of these and that they have a reduced capacity to detoxify these substances as opposed to other odontocetes (Muir et al. 1992). Norstrom and Muir (1994) obtained data on the temporospatial distribution of PCBs and other contaminants in ringed seal, beluga, polar bear and narwhal. On a fat weight basis, the sum of DDT-related compounds (S-DDT) and PCB levels are lowest in walrus (<0.1 µg/g), followed by ringed seal, (0.1-1 µg/g range). Levels are an order of magnitude higher in beluga and narwhal (1-10 µg/g range). It appears that metabolism and excretion of S-DDT and PCBs may be less efficient in cetaceans, leading to greater biomagnification.

7. Remarks
According to Reyes (1991) the Fisheries Act of 1976 set out the Narwhal Protection Regulations for protection of habitat and management of the species in Canada. Regulations include the setting of quotas and confer total protection to mothers and calves, but due to inadequate enforcement, quotas are exceeded and nursing females are taken. Hunters are required to make full use of the carcasses and to attach tags to every tusk obtained and to every toothless female or young male killed. However, this regulation is only partially observed. There are no specific regulations for narwhal hunting in Greenland, although Inuit have themselves forbidden the use of motor boats in the narwhal hunting areas in summer. Narwhals are protected in the United States, with some exemptions for subsistence hunting. Full protection is also provided in the USSR and Norway (Reyes, 1991).

At the international level, the IWC Scientific Committee (2000) recommended that genetic and telemetric studies are needed to identify stocks, and improved catch-reporting (including estimation of hunting loss) should be conducted in Canada and Greenland.

Information on life history, distribution, abundance and actual hunting loss rates are needed to assess and manage the stocks. The probable effects of pollution, industrial development and climatic change should be fully studied, since these may represent a potential threat.

The narwhal is categorized as ‘Insufficiently Known” (DD) by the IUCN (see “links”. The species is included in Appendix II of CMS.

Range States are Canada, Denmark (Greenland), Iceland, Norway (Svarlbard), the United States (Alaska) and the USSR (CMS, 1988).

8. Sources
- Anonymous (1997) Greenland - progress report on marine mammal research 1994. Annu Rep Nammco 1996, pp. 185-188.
- Born EW (1994) Monodon monoceros Linnaeus, 1758 - Narwhal. In: Handbuch der Säugetiere Europas. Meeressäuger. Teil IA: Wale und Delphine 1 (Robineau D, Duguy R and Klima M, Eds.) Aula-Verlag, Wiesbaden. pp. 209 - 240.
- Dietz R, Heide-Joergensen MP, Richard PR, Acquarone M (2001) Summer and fall movements of Narwhals (Monodon monoceros) from northeastern Baffin Island towards northern Davis Strait. Arctic 54: 244-261
- Gjertz I (1991) The narwhal, Monodon monoceros , in the Norwegian High Arctic. Mar Mamm Sci 7 (4): 402-408.
- Gray RW (1931) The colour of the Greenland Sea and the migration of the Greenland whale and narwhal. Geogr J 78: 284-290.
- Hay KA (1985) The life history of the narwhal (Monodon monoceros L.) in the eastern Canadian Arctic. Diss Abst Int Pt B Sci and Eng 45 (10).
- Hay KA, Mansfield AW (1989) Narwhal - Monodon monoceros Linnaeus, 1758. In: Handbook of Marine Mammals (Ridgway SH, Harrison SR eds.) Vol. 4: River Dolphins and the Larger Toothed Whales. Academic Pres, London, pp. 145 - 176.
- Heide-Jorgensen MP (2002) Narwhal- Monodon monoceros. In: Encyclopedia of marine mammals (Perrin WF, Würsig B, Thewissen JGM, eds.) Academic Press, San Diego, 783-787.
- Heide-Jorgensen MP, Dietz R (1995) Some characteristics of narwhal, Monodon monoceros, diving behaviour in Baffin Bay. Can J Zool 73 (11): 2120-2132.
- IWC, 2000. Report of the Scientific Committee from its Annual Meeting 3-15 May 1999 in Grenada. J. Cetacean Res. Manage. 2 (Suppl)
- Jefferson TA, Leatherwood S, Webber MA (1993) FAO Species identification guide. Marine mammals of the world. UNEP / FAO, Rome, 320 pp.
- Muir DCG, Ford CA, Grift NP, Stewart REA, Bidleman TF (1992) Organochlorine contaminants in narwhal (Monodon monoceros) from the Canadian Arctic. Environ Pollut 75 (3): 307-316.
- Norstrom RJ, Muir DCG (1994) Chlorinated hydrocarbon contaminants in Arctic marine mammals. Sci Total Environ 154 (2-3) 107-128.
- Palsboll PJ, Heide Jorgensen MP, Dietz R (1997) Population structure and seasonal movements of narwhals, Monodon monoceros, determined from mTDNA analysis. Heredity 78(3): 284 292.
- Reeves RR (1992) Recent developments in the commerce in narwhal ivory from the Canadian Arctic. Arct Alp Res 24 (2): 179-187.
- Reyes JC (1991) The conservation of small cetaceans: a review. Report prepared for the Secretariat of the Convention on the Conservation of Migratory Species of Wild Animals. UNEP / CMS Secretariat, Bonn.
- Rice DW (1998) Marine mammals of the world: systematics and distribution. Society for Marine Mammalogy, Special Publication Number 4 (Wartzok D, Ed.), Lawrence, KS. USA.
- Roberge MM, Dunn JB (1990) Assessment of the subsistence harvest and biology of narwhal (Monodon monoceros L.) from Admiralty Inlet, Baffin Island, N.W.T., 1983 and 1986-89. Can Tech Rep Fish Aqaut Sci 1747, 38 pp.
- Strong JT (1988) Status of the narwhal, Monodon monoceros , in Canada. Can Field Nat 102 (2): 391-398.
- Turl CW (1987) Winter sightings of marine mammals in Arctic pack ice. Arctic 40: 219-220

- A Special Thanks to Boris Michael Culik at WCMC http://www.wcmc.org.uk/cms/reports/small_cetaceans/comments.htm