Boreal whale characteristics, habitat, feeding, reproduction

1589
Anthony Golden

The boreal whale or from Greenland (Balaena mysticetus) is a placental mammal that is part of the Balaenidae family. This species has very particular characteristics, such as the lack of the dorsal fin, the triangular head and its enormous size..

However, the most outstanding feature of this cetacean is the morphology of its jaws. The lower one is U-shaped, while the upper one is narrower and, viewed from above, resembles a V. The body coloration is predominantly black, but the chin is white with dark gray or black spots..

Boreal whale. Source: NOAA United States. National Marine Fisheries Service [Public domain]

The Arctic whale, as this mysticete is also known, is endemic to cold Arctic and sub-arctic waters. Their populations have decreased, due to various factors such as ocean acidification. This has caused the UIN to include it in its list of species at risk of extinction.

Article index

  • 1 Behavior
  • 2 General characteristics
    • 2.1 Size
    • 2.2 Head
    • 2.3 Coloring
    • 2.4 Body
    • 2.5 Maxillary corpus cavernosum
  • 3 Conservation status
    • 3.1 - Threats
    • 3.2 - Actions
  • 4 Habitat and distribution
    • 4.1 Current populations
  • 5 Food
    • 5.1 Feeding methods
  • 6 Playback
  • 7 References

Behaviour

The Greenland whale is not a social animal. It generally travels alone or in small herds. It is able to dive and stay submerged for up to an hour. According to experts, this species does not make deep dives, but can reach 150 meters.

Balaena mysticetus It is a slow swimmer, normally moving between 2 and 5 km / h. While feeding, the speed increases from 3.96 to 9 km / h. When you are in danger, you can do it faster, at 10 km / h.

These cetaceans are very vocal, using low-frequency sounds to communicate while socializing, feeding, or during migrations. In the breeding season, the males emit complex songs. These mating calls are long and varied. They are used mainly to attract females.

General characteristics

Size

This species is the second largest in the world, surpassed by the blue whale (Balaenoptera musculus). The female of the boreal whale is slightly larger than the male.

Thus, these measure from 16 to 18 meters, while the male reaches a length between 14 and 17 meters. In relation to weight, it ranges from 75,000 to 100,000 kilograms.

Head

The Balaena mysticetus It has a large head, with a skull that measures about a third of the total length of the body. This bone structure is asymmetric and is used to break up the Arctic ice masses, in order to be able to go out to breathe.

The mouth is long and arched, and can measure up to 4.3 meters. Inside is the tongue, which weighs around 907 kilograms. As for the upper jaw, it is narrow and V-shaped, while the structure of the lower jaw is similar to a U. The eyes are located above the vertex of the mouth..

The Greenland whale has two spiracles on the top of its head. Through these, when breathing, a blow of water up to 6.1 meters high can be thrown.

This cetacean lacks teeth. Instead, it has between 230 and 360 beard plates, which are up to 30 centimeters wide and 4.3 long. The beards are made of keratin, are black or dark gray in color and end in long, fine fringes..

Coloration

The boreal whale has a black body, with a large white spot with dark gray dots on the lower jaw. Also, it has a white or light gray stripe on the edge of the tail and around the fins. These bands expand with age, so that, in the adult, the tail can become almost white.

Body

The Balaena mysticetus It is characterized by having a large and robust body. This species lacks a dorsal fin and the pectoral fin is small, measuring less than 2 meters..

On the other hand, it has a thick layer of insulating grease, which can be up to 50 centimeters thick. This allows the animal to survive in the cold waters where it lives.

Maxillary cavernous body

This reticular palatal organ is located along the rostral palate, thus forming two lobes. Research results indicate that it is made up of highly vascular tissue, similar to the corpus cavernosum of the mammalian penis..

Experts presume that this structure works as a cooling mechanism for the organism of this cetacean. During the physical efforts of swimming, the Greenland whale must cool down, to avoid hyperthermia and possible brain damage.

This presumably is accomplished when the maxillary corpus cavernosum fills with blood, causing the animal to be forced to open its mouth. In this way, the cold water from the sea enters the oral cavity, which, when flowing over the organ, cools the blood.

State of conservation

Boreal whale populations are exposed to various threats, such as ocean acidification and collisions with large vessels. Such accidents can cause serious injury or kill the animal.

This has caused the communities to be declining, which is why the IUCN has included this species in the list of animals at risk of extinction..

- Threats

Incidental hunting

About 12% of the species that inhabit the western Arctic are scarred, usually caused by fishing gear. Greenland whales swim with their net tangled around their bodies or they may stay anchored somewhere. This can cause serious injury or death..

Contamination

Pollutants, such as DDT and oil, reach the ocean through the discharge of wastewater, oil spills and through maritime transport, among others..

Thus, toxic substances accumulate in the prey, which, when consumed by the cetacean, is progressively deposited in some organs. This can cause damage to the immune and reproductive systems, causing the death of the animal..

Sonic pollution, produced by seismic explorations and by vessels, disrupts the normal behavior of the boreal whale. Also, it moves the animal away from regions important for its survival..

- Actions

The Balaena mysticetus It is legally protected since 1948 by the International Convention for the Regulation of whaling. In addition, since 1975 it has been included in Appendix I of the Convention on International Trade in Endangered Species.

On the other hand, the boreal whale is under the national legislation of threatened species in Canada, the United States and the Russian Federation.

Habitat and distribution

This species is the only baleen whale that lives its entire life in subarctic and arctic waters. Their home range varies according to climate change and the formation or melting of the ice sheet..

The Greenland whale winters in the areas near the southern edge of the ice. When it breaks, it moves north. Thus, the Alaskan population lives during the cold months in the southwestern Bering Sea. This group migrates north in the spring, after the ice has opened in the Beaufort and Chukchi Seas..

The historical distribution during the 16th and 17th centuries may have been much more extensive and southern. This is supported by reviews of the presence of this marine mammal in Newfoundland and Labrador, in eastern Canada, and in the Gulf of Saint Lawrence, in eastern Canada..

However, fossil records indicate that in the Pleistocene they lived much further south, inhabiting North Carolina and Italy..

Current populations

Currently, experts recognize five populations worldwide. One of these is located west of Greenland, in Hudson Bay and in the Foxe Basin. A group is found in eastern Canada, in Davis Strait and Baffin Bay.

Also, it extends from the waters of eastern Greenland and Spitsbergen to eastern Siberia. In the northwestern Pacific Ocean it lives in the Sea of ​​Okhotsk.

The only community that is distributed in the waters of the United States is the western Arctic. This is known as the Bering- Beaufort- Chukchi population..

Feeding

The diet of the boreal whale is mainly made up of crustaceans and benthic and epibenthic organisms These include copepods, opossum shrimp (order Mysidacea), krill (order Euphausiacea) and amphipods.

In relation to the copepods, they are not the main source of nutrients in the young, but their nutritional importance increases as the animal becomes an adult. At this stage of life, this cetacean can filter around 50,000 of these crustaceans every minute.

Feeding methods

Daily, this species consumes about two short tons of food. To capture prey, it can be done alone or sometimes in groups of two to ten cetaceans. The members of this group swim at the same speed, organizing themselves in a staggered way, in the shape of a V.

The Balaena mysticetus it captures its prey in the columns of water and on the surface. However, recent research indicates that it also does so in areas close to the seabed. But, unlike the gray whale, it does not ingest food directly from the ocean floor..

The Greenland whale is filter feeder. For this, the cetacean has hundreds of baleen plates, which hang from the upper jaw. In addition, the mouth has a large lip on the lower jaw, which is oriented upwards..

This strengthens and supports the beards. Also, it prevents them from sagging or breaking, due to the pressure exerted by the water that passes through the barbs..

To feed, the animal swims forward with its mouth open, thus allowing a large amount of water to enter the oral cavity. The tongue then pushes the water against the baleen plates, trapping the prey inside the mouth.

Reproduction

The boreal whale reaches sexual maturity between 10 and 15 years, when its body measures 12.3 to 14.2 centimeters. Mating generally occurs in pairs, but can eventually occur between one male and two females..

The male exhibits behaviors associated with courtship, attracting the female through vocalizations. The beginning of the reproductive season occurs between the end of winter and the beginning of spring. Shortly after mating, northward migration occurs.

After a gestation period, which lasts between 13 and 14 months, the calf is born. This is about 4 to 4.5 centimeters long and weighs about 1,000 kilograms. Its growth is rapid, since during the first year of life they increase 8.2 meters.

Breastfeeding lasts about a year. After weaning, the growth rate noticeably slows down. To survive the low temperatures of the water, the young are born with a thick tissue of fat. So after 30 minutes of being born, the baby swims alone.

References

  1. Justice, J. (2002). Balaena mysticetus. Animal Diversity Web. Recovered from animaldiversity.org.
  2. Wikipedia (2019). Bowhead whale. Recovered from en.wikipedia.org.
  3. NOAA Fisheries (2019). Bowhead W Recovered from fisheries.noaa.gov.
  4. FAO (2020). Balaena mysticetus (Linnaeus, 1758). Recovered from fao.org.
  5. MARINEBIO (2019). Bowhead Whales, Balaena mysticetus. Recovered from marinebio.org.
  6. Cooke, J.G., Reeves, R. (2018). Balaena mysticetus. The IUCN Red List of Threatened Species 2018. Recovered from iucnredlist.org.
  7. Outi M. Tervo, Mads F. Christoffersen, Malene Simon, Lee A. Miller, Frants H. Jensen, Susan E. Parks, Peter T. Madsen (2012). High Source Levels and Small Active Space of High-Pitched Song in Bowhead Whales (Balaena mysticetus). Recovered from journals.plos.org.
  8. David J. Rugh, Kim E.W.Shelden (2009). Bowhead Whale: Balaena mysticetus. Recovered from sciencedirect.com.

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