Narwhal characteristics, habitat, reproduction, behavior

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Sherman Hoover
Narwhal characteristics, habitat, reproduction, behavior

The narwhal (Monodon monoceros) is a cetacean that belongs to the Monodontidae family. Its main characteristic is that the male has a huge tusk in the upper jaw, which grows horizontally, in relation to the skull. This crosses the lip and projects out of the body of the animal.

This tooth can be up to 3 meters long and develops continuously throughout life. In the mouth, this placental mammal has another canine, but smaller.

Narwhal. Source: G. M. [Public domain]

The narwhal is an animal that needs to rise to the surface of the water to take in oxygen. Its body is robust and bluish-gray in color, a tone that becomes lighter as it ages. On the sides and back it has black spots, which give it a mottled appearance.

This species is distributed in the Arctic Circle. Thus, it mainly ranges from the Canadian Central Arctic to the Russian Central Arctic and Greenland..

The Monodon monoceros it is a seasonal migratory animal. In the summer, it travels in groups to coastal waters, while in the winter it moves to open regions, in whose waters there are masses of ice.

Article index

  • 1 Features
    • 1.1 - Coloring
    • 1.2 - Size
    • 1.3 - Body
    • 1.4 - Organic adaptations
    • 1.5 - Teeth
    • 1.6 - Predation
    • 1.7 - Communication
  • 2 Taxonomy
  • 3 Habitat and distribution
    • 3.1 - Seasonal migrations
  • 4 State of conservation
    • 4.1 Hunting
    • 4.2 Environmental degradation
    • 4.3 Climate change
    • 4.4 Actions
  • 5 Playback
    • 5.1 The breeding
  • 6 Food
    • 6.1 Factors
  • 7 Behavior
    • 7.1 Echolocation
  • 8 References 

Characteristics

Dr. Kristin Laidre, Polar Science Center, UW NOAA / OAR / OER [Public domain]

- Coloration

The newborn is a bluish-gray or gray hue. The coloration becomes lighter with age. Thus, in the adult stage, the ventral area of ​​the narwhal is creamy yellow or white, while black spots appear on the back and sides, giving them a mottled appearance..

Older animals are generally almost white, although they may maintain some black tones in the appendages. When they are sexually mature, clear patches appear on the genital cleft and navel.

- Size

Chris huh [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/)]

The narwhal is a medium-sized whale. The calf, at birth, weighs around 80 kilograms and is 1.6 meters long. The adult female is usually slightly smaller than the male. This can reach up to 5.5 meters in length and weigh approximately 1.94 kilograms.

On the other hand, the female has a length, considering her head and body, of 4.9 meters. As for its weight, it is 1.55 kilograms. In both sexes, about a third of the weight is adipose tissue.

In relation to the pectoral fin, it measures between 30 and 40 centimeters and the extension of the tail fins has a length of 100 to 120 centimeters.

- Body

The body is robust, with a relatively small head and a flattened muzzle. The cervical vertebrae are articulated, as occurs in land mammals. In contrast, in the vast majority of whales and dolphins, these bones, which are part of the neck, are fused.

The Monodon monoceros it lacks a dorsal fin, which could be due to an evolutionary adaptation to easily swim under ice. However, it usually has a slight dorsal ridge. This is irregular in shape and measures 5 centimeters high and between 60 and 90 centimeters long.

In the adult, the fins become somewhat concave and straight at the leading edge and convex towards the trailing edge..

The tail fin has convex posterior margins, rather than being straight or concave, as is the case in almost all cetaceans. In the female, the tail has front edges that are swept back, while in the male the margins are slightly more concave..

Specialists suggest that this characteristic of the tail contributes to reducing the resistance caused by the large tusk..

- Organic adaptations

Under the skin, this aquatic mammal has a thick layer of adipose tissue, which acts as an insulating element from the external cold, typical of the waters where it lives..

In addition, the fat tissue is a storehouse of nutrients, which the narwhal will use in case the availability of food decreases..

Another organic adaptation occurs in the fins. In these, the incoming arteries and outgoing veins are closely arranged, allowing countercurrent heat exchange.

In this way, when the narwhal swims in warmer waters, it can expel the heat generated by swimming to forage or during migrations..

- Teeth

This species has only two canine teeth, located on the upper jaw. In the female, these are generally not functional and are embedded in the maxilla. On the contrary, in the male the right tooth is kept in the jaw, while the left one protrudes from the upper lip, growing forward.

The far end of these teeth has a polished appearance, while the rest may be covered in a reddish or greenish growth due to algae. This bone structure can be broken, however, the damaged area is usually replaced by growth of dentin..

Canine

The main characteristic of Monodon monoceros is that the male has a long tusk, which projects from the left area of ​​the upper jaw, through the lip, forming a helical spiral. This particular tooth grows throughout life, reaching an approximate length of 1.5 to 3.1 meters.

It is hollow and its weight is 10 kilograms. This does not grow curved down, as occurs in other mammals such as the walrus. Its development is completely horizontal, in relation to the skull, so it breaks the upper sage. The outer part is porous, with a hard enamel layer.

Only about 15% of females have a tusk, which is usually smaller and less noticeable spiral than that of the male..

Utility

The fang of the narwhal is a sensory organ. In the center of the tooth there is a pulp, rich in blood vessels and nerve endings, which are responsible for connecting the stimuli received from the outside environment with the brain.

Nearly ten million nerve connections tunnel from the central nerve of the tusk to the outer surface. Thus, the rubbing of these long canines with the water is a way for the narwhal to obtain information from the outside, such as depth, water pressure, salinity and temperature.

However, the researchers, while observing the feeding behavior of this mammal, observed that it used its tusk to hit and stun the Arctic cod. In this way, he was able to capture them more easily and then ingest them.

Another group of experts proposes that the tusk has an element of sexual selection. By displaying it during courtship, you may attract the female in heat. There is no reference that these are used in combative behavior, although sometimes the males touch their fangs, but not with fighting intentions..

- Predation

The main predator of the narwhal is the polar bear, which attacks it by inserting its powerful front legs into the breathing holes that exist in the Arctic ice. Other animals that pose a threat to this cetacean are Greenland walruses and sharks..

Also, killer whales often gather to stun groups of narwhals found in shallow water in closed bays. In one attack, orcas could kill dozens of these cetaceans.

To flee the attack, the Monodon monoceros can dive for a long time, thus hiding from predators.

- Communication

Like the vast majority of toothed whales, the narwhal uses sound to hunt and navigate. This occurs when the air passes through the chambers, close to the blow hole, reflecting in the frontal area of ​​the skull.

Some of these vocalizations are whistles, clicks, and thumps. The click is often used for echolocation and to locate obstacles that are at close range. To hunt, it first regularly emits several slow clicks. This first stage is associated with the search for the prey.

Once it finds it, the narwhal quickly vocalizes a series of very fast clicks, thus reducing the time in which it receives the location response from the prey. After this, nothing towards it to capture it.

Regarding the sound of blow, some specialists associate it with hunting, since they disorient the prey, making it easier to capture. As for the hiss, they are used infrequently, compared to those emitted by the beluga (Delphinapterus leucas).

Taxonomy

-Animal Kingdom.

-Subkingdom: Bilateria.

-Phylum: Chordate.

-Subfilum: Vertebrate.

-Superclass: Tetrapoda.

-Class: Mammalia.

-Subclass: Theria.

-Infraclass: Eutheria.

-Order: Cetacea.

-Suborder: Odontoceti.

-Family: Monodontidae.

-Genre: Monodon.

-Species: Monodon monoceros.

Habitat and distribution

Authorship: Pcb21, wikimediacommons

The Monodon monoceros it lives in arctic waters, generally those that are above 61 ° north latitude. Its main distribution ranges from the Canadian central Arctic to Greenland.

It also inhabits northeastern Canada, Nunavut, the western region of Greenland, the northern waters of Russia, and the eastern Siberian Sea. Although it is an arctic species, some wandering narwhals can be sighted off the coast of Newfoundland, in the Mediterranean Sea and in Europe.

They are rarely seen in the East Siberian Sea, western Arctic Canada, Chukchi, Bering, Alaska, and Beaufort.

In relation to Canada, there are two populations, based on their distribution during the summer. One of these is in Baffin Bay, where it occupies the northern area. The other grouping of narwhals is in Hudson Bay, located in the south of the region..

Some of the factors that influence habitat selection are its quality and the density of the ice. Narwhal is rarely found far from loose ice, where there are holes that allow them to breathe. Also, they prefer deep waters.

- Seasonal migrations

Dr. Kristin Laidre, Polar Science Center, UW NOAA / OAR / OER [Public domain]

The Monodon monoceros presents annual migrations. During the summer it moves in groups of 10 to 100 narwhals towards coastal waters. In the winter it migrates to open and deep waters, which are under a thick layer of ice.

When spring arrives, these ice masses open up, forming channels, allowing the animal to return to the coastal bays..

Winter

Narwhal that inhabit western Greenland and Canada winters in Davis Strait and Baffin Bay. This marine mammal has a remarkable fidelity to these winter areas.

During the fall and winter, this animal is vulnerable to ice traps. This occurs when weather conditions change abruptly, causing the open waters to freeze and trap you. This could lead to the death of the cetacean by suffocation..

Summer

In the summer, the ice cover is reduced, leading the narwhal to move to smaller bodies of water, such as the headwaters of the fjords. The largest, and probably best known, population at this time of year is northeast of Greenland and east of the Canadian Arctic..

During the summer period, the Canadian Arctic is home to approximately 90% of the world's population of Monodon monoceros. Thus, they can congregate north of Ellesmere Island and Hudson Bay, where they feed and pregnant females give birth to their young..

In some parts of this summer range, it can aggregate on the various tidal glacier fronts. In the fall, narwhals move to the winter areas, in deep, ice-covered waters, located along the entire continental slope..

State of conservation

In earlier times, the population of the narwhal was below 50,000 thousand animals, so the IUCN had classified this species as near threatened.

However, recently estimates indicate that the communities present higher numbers, which is why this organization currently considers it as less concern of becoming extinct..

In relation to Canada, this species is considered by COSEWIC among the species with special extinction concerns. Likewise, the pertinent evaluations are being carried out to include it in the Federal Law of Species at Risk..

Some of the main threats this species faces are:

Hunting

The narwhal is hunted, because the man trades some of the parts of his body. For example, meat and fat are consumed and the skin is considered an important source of vitamin C. Likewise, the long tusk and vertebrae are sold natural or carved..

This species is not subject to large-scale hunting, except in the Canadian Arctic region in the early 20th century. In the first decades of that century, this cetacean was opportunistically hunted by explorers and commercial whalers..

At present, the Monodon monoceros It is hunted only in some indigenous communities in Greenland and Canada, both for its consumption and to market its tusk.

Degradation of the environment

Globally, the oceans are polluted by industrial waste. Thus, the presence of mercury, cadmium and organochlorine substances in the water, cause the accumulation of these elements in the animal's body. This seriously affects their health and reproductive performance..

Another pollutant is underwater noise. Narwhals move away from feeding and calving areas when large vessels are found in these areas.

The development of oil and gas areas, together with the transportation of their commercial products, are altering and degrading the natural habitat. In this sense, some regions of Arctic Russia and Greenland are subject to the development of oil and gas complexes. This entails seismic studies, artificial island construction and offshore drilling..

According to scholars of the matter, the noise produced by these activities could increase the susceptibility of the narwhal to being trapped in ice blocks..

Climate change

According to specialists, the Arctic is warming twice as much as the rest of the planet. This situation puts the narwhal at risk.

For decades, sea ice has been reduced by around 13.4%, which directly affects this cetacean. It uses the masses of ice to evade predators and to hunt, in addition to being its habitat during winter.

In this sense, research on the sensitivity of marine mammals that inhabit the Arctic, classifies the narwhal within the three most sensitive species. This is due to its narrow geographical distribution, its high fidelity to migratory areas and its highly specialized diet..

An indirect threat of snowmelt is increased exposure of the animal to open water. This increases the chance of being caught by hunters..

Actions

The Monodon monoceros It is within the group of species that are protected by CITES, as contemplated in Appendix II. Because of this, the governments of Greenland and Canada are required to document records of catch, abundance, trade, and population trends of this cetacean..

Reproduction

The male is sexually mature approximately between 11 and 13 years, when his body measures around 3.9 meters. As for the female, it reaches maturity when it is 5 to 8 years old and has an approximate length of 3.4 meters long..

Mating generally occurs in spring, usually in the month of May. During courtship, males show their fangs to females in heat, with the intention of attracting them and forming a mate..

As for copulation, it occurs in the water. The male and female stand upright, joining their bellies. In a high percentage, the fertilized ovum implants in the left uterine horn.

Gestation lasts between 13 and 16 months, so delivery occurs from July to August of the following year. As in the case of the vast majority of marine mammals, only one calf is born. In childbirth, the first part that is expelled from the womb is the tail.

The brood

The newborn is approximately 1.5 to 1.7 meters long and weighs approximately 80 kilograms. At birth, your body already has adipose tissue, with a thickness of 25 millimeters. This thickens as they feed on breast milk, which is rich in fat..

Shortly after being born, the young man is able to swim. The female suckles it for 20 months, during which time the calf learns the skills necessary to survive in the environment that surrounds it..

Feeding

The narwhal's diet is very varied. This includes mollusks, crustaceans, cephalopods, squid, and fish, including the Greenland halibut (Reinhardtius hippoglossoides) and arctic cod (Boreogadus saida).

Also, eat salmon, sole, turbot (Reinhardtius hippoglossoides), the polar cod (Arctogadus glacialis), cuttlefish and herring. Likewise, it includes deep-sea fish such as halibut and red fish (Sebastes marinus), which indicates that this species can dive deeper than 500 meters.

Due to its poor dentition and the poor functionality of the tusks, experts suggest that the narwhal sucks its prey, after pursuing them by swimming..

In addition, as a feeding strategy, to discover the prey that are on the ocean floor, it could produce a strong jet of water with its mouth. The flexibility of its neck allows it to visualize wide areas, in search of its food. It also uses echolocation to find its prey.

Factors

Their diet is seasonal and also depends on the region where they live. In the spring, he usually eats cod, which he takes from the edges of the sea ice. During the summer season, food consumption decreases significantly. However, it tends to capture prey opportunistically.

Foraging resumes in the fall, while the Monodon monoceros moves south, reaching its maximum feeding point in winter. In this season of the year, it feeds on species that live on the seabed, however, some subpopulations could feed on pelagic prey.

The diet could also vary periodically. Thus, according to studies carried out, in 1978 the Arctic cod (Boreogadus saida) constituted 51% of the diet, followed by Greenland halibut (Reinhardtius hippoglossoides), which was consumed by 37%.

After one year, these percentages varied. Arctic cod accounted for 57%, while Greenland halibut for 29%.

Behaviour

The Monodon monoceros it is a gregarious species that generally forms groups of up to 20 animals. These are usually segregated according to sex. Thus, they can be formed only by females, young or adult males, although it could also be the case that they are mixed.

During migrations, smaller groups join with others, thus forming large herds. These can contain from 500 to more than 1000 narwhals.

On occasion, the male may rub his large tusk against that of another male. Some experts consider that this exhibition is intended to establish the domain hierarchy in the group. However, others attribute it to the use of the tusk as a sensory and communication organ.

Echolocation

The narwhal has the ability to emit sounds that allow it to know the environment around it. When the emitted beam bounces off an object, specialized sensory organs pick up the echo, which is interpreted by the brain.

In this way, the animal can know the distance in which the other body is, by measuring the delay suffered by the emitted and received signals.

In an investigation carried out in Baffin Bay, Greenland, the echolocation signals emitted by the narwhal were recorded. The data showed that these had a beamwidth of approximately -3 dB of 5.0 °.

This makes this biosonar signal the most directional currently reported in any species. Likewise, another characteristic of the echolocation signals emitted is the evidence of a ventral-dorsal asymmetry, with a narrower beam on the axis..

This particularity could constitute an evolutionary advantage, since it contributes to the reduction of the echoes from the surface of the water or sea ice. During the swim, while the narwhal moves ascending and descending, it performs a vertical scan at the same time, for which it uses the sonar beam..

References

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