por He 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 is projected towards the outside of the animal’s body.
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.
The narwhal is an animal that needs to come 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.
He Monodon monoceros It is a seasonal migratory animal. In the summer, it travels in groups towards coastal waters, while in the winter it moves to open regions, in whose waters there are masses of ice.
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Characteristics
– Coloring
The newborn is a bluish-grey or gray shade. The coloration becomes lighter with increasing 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 retain some shades of black on the appendages. When they are sexually mature, light patches appear on the genital cleft and on the umbilicus.
– Size
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 its head and body, of 4.9 meters. As for her weight, it is 1.55 kilograms. In both sexes, about a third of the weight is adipose tissue.
Regarding the pectoral fin, it measures between 30 and 40 centimeters and the extension of the tail fins is 100 to 120 centimeters long.
– Body
The body is stout, with a relatively small head and a flattened snout. The cervical vertebrae are articulated, as in terrestrial mammals. On the contrary, in the vast majority of whales and dolphins, these bones, which are part of the neck, are fused together.
He Monodon monoceros it lacks a dorsal fin, which could be due to an evolutionary adaptation to easily swim under the 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 caudal fin has convex trailing margins, rather than being straight or concave in shape, as is the case in most 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.
Furthermore, fatty tissue is a storehouse of nutrients, which the narwhal will use in case food availability decreases.
Another organic adaptation occurs in the fins. In these, the incoming arteries and the outgoing veins have a very close arrangement, which allows 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 in the upper jaw. In the female these are generally non-functional and embedded in the maxilla. On the contrary, in the male the right tooth remains in the jaw, while the left protrudes from the upper lip, growing forward.
The distal end of these teeth has a polished appearance, while the rest may be covered with a reddish or greenish growth due to algae. This bone structure can break down, however the damaged area is often replaced by dentin growth.
Canine
The main feature of the 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 downwards, as occurs in other mammals such as the walrus. Its development is completely horizontal, in relation to the skull, which is why it breaks the upper sage. The external part is porous, with a hard enamel layer.
Only about 15% of females have a tusk, which is usually smaller and less noticeably spiraled than the male’s.
Utility
The tusk 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.
Almost ten million nerve connections make a kind of tunnel from the central nerve of the tusk to the outer surface. Thus, the friction 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 strike and stun 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, it could attract the female in heat. There is no reference that these are used in combative behaviors, although sometimes the males touch their fangs, but not with fighting intentions.
– Predation
The narwhal’s main predator is the polar bear, which attacks it by inserting its powerful front paws into breathing holes in the arctic ice. Other animals that pose a threat to this cetacean are walruses and Greenland sharks.
Also, killer whales often gather to stun pods of narwhals in shallow water in enclosed bays. In one attack, orcas could kill dozens of these cetaceans.
To escape the attack, the Monodon monoceros It can submerge for a long time, thus hiding from its predators.
– Communication
Like the vast majority of toothed whales, the narwhal uses sound for hunting and navigation. This is produced 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 hissing, clicking, and thumping. Clicking is often used for echolocation and locating obstacles within a short distance. To hunt, it first regularly emits several slow clicks. This first stage is associated with the search for the prey.
Once found, the narwhal quickly vocalizes a series of very rapid clicks, thus reducing the time in which it receives a location response from prey. After this, swim towards it to capture it.
Regarding the sound of a blow, some specialists associate it with hunting, since it disorients the prey, making it easier to capture. As for the whistle, they are used infrequently, compared to those emitted by the beluga (Delphinapterus leucas).
taxonomy
-Animal Kingdom.
-Subkingdom: Bilateria.
-Filum: Chordate.
-Subphylum: Vertebrate.
-Superclass: Tetrapoda.
-Class: Mammalia.
-Subclass: Theria.
-Infraclass: Eutheria.
-Order: Cetacea.
-Suborder: Odontoceti.
-Family: Monodontidae.
-Genus: Monodon.
-Species: Monodon monoceros.
Habitat and distribution
He Monodon monoceros lives in arctic waters, generally those above 61° north latitude. Its main distribution ranges from the Canadian central Arctic to Greenland.
Also inhabits northeastern Canada, Nunavut, western Greenland, northern Russian waters, and eastern Siberian Sea. Although it is an arctic species, some wandering narwhals can be seen off the coast of Newfoundland, in the Mediterranean Sea and in Europe.
They are rarely seen in the East Siberian Sea, Canada’s western Arctic, 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 ice density. Narwhals are rarely found far from loose ice, where there are holes that allow them to breathe. Also, they prefer deep water.
– Seasonal migrations
He Monodon monoceros It has annual migrations. During the summer it moves in groups of 10 to 100 narwhals towards coastal waters. In the winter it migrates to deep open water, which is under a thick layer of ice.
When spring arrives, these ice masses open up, forming channels, allowing the animal to return to coastal bays.
Winter
The narwhal found in western Greenland and Canada winters in Davis Strait and Baffin Bay. This marine mammal has a remarkable fidelity to these wintering areas.
During the fall and winter, this animal is vulnerable to ice entrapment. This occurs when weather conditions change abruptly, causing the open water to freeze over and trap you. This could cause the death of the cetacean by suffocation.
Summer
In the summer, the ice cover reduces, leading the narwhal to move to smaller bodies of water, such as the headwaters of fjords. The largest, and probably best known, population at this time of year is in northeast 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 parts of this summer range, it may aggregate at the various tidal glacier fronts. In the fall, the…