FIN WHALE: CHARACTERISTICS, HABITAT, FEEDING, REPRODUCTION - BIOLOGY - 2024

The fin whale (Balaenoptera physalus) is a marine mammal that is part of the Balaenopteridae family. This species is distinguished from the rest of the mysticetes by its slim body, which, in the dorsal area is brown or dark gray, while ventrally it is white. Also, he has a white spot on his lower right jaw.

Its snout is flattened and contains keratinized beards, which replace teeth. These structures function as filters, which allow the crustaceans and squid to be separated from the water when it enters the mouth of the cetacean.

Fin whale. Source: NOAA United States. National Marine Fisheries Service

Regarding its distribution, the fin whale is found in temperate and subpolar waters worldwide. Some have migratory behaviors. Thus, they move between feeding areas, at high latitudes, and reproductive areas, located at low latitudes.

Vocalizations

Male Balaenoptera physalus emit loud, long, low-frequency sounds between 16 and 40 Hz. They also produce patterned, simple pulses of 20 Hz. Each of these can last from one to two seconds. She is also capable of vocalizing various combinations, in sequences of 7 to 15 minutes.

Then, this cetacean repeats these calls when it is in the reproductive stage or during fighting.

In a study conducted, researchers indicated that fin whales use counter-call. This method used to communicate consists of a cetacean making a sound and another responding to it. In this way, they both obtain information about the environment.

characteristics

Beard plates

The fin whale lacks teeth. In replacement of these, it has two parallel rows of blades in the upper jaw, known as barbs. These are flexible, smooth and have frayed edges. Its main component is keratin, which gives it a certain degree of hardness.

In the fetal stage, this mysticete has small teeth. However, these disappear progressively during the development process. At birth, they have already been completely replaced by beards.

This species has between 350 and 400 barbs, which are used in the feeding process. Each plate measures up to 76 centimeters in length and 30 centimeters in width.

Body

The body of the Balaenoptera physalus is thin and long. In the lower area it has between 56 and 100 folds, which extend from the chin to the middle of the ventral region. These grooves allow the throat and mouth to expand during feeding.

The dorsal fin is curved and measures 26 to 75 centimeters. This is visible when the mammal comes to the surface. As for the tail, it is wide, pointed and has notches in the center.

Head

The head is flat and its size is approximately 1/5 of the total length of the body. The fin whale has two spiracles and a longitudinal crest, which extends from the snout to the spiracles. The rostrum is wide, flat and V-shaped.

Size

The finned whale, as this species is also known, is the second largest mammal, after the blue whale. In general, it grows up to approximately 20 and 25 meters long and its weight ranges from 70,000 kilograms. The size varies remarkably, according to the geographic region that the animal inhabits.

Thus, those that are distributed in the northern hemisphere measure from 18.5 to 20 meters, with an average weight of 38.5 to 50.5 tons. As for those of the southern hemisphere, their bodies have a length of 20.5 to 22 meters and the mass is from 52.5 to 63 tons.

Coloration

The dorsal area of ​​this species can be from leaden gray to dark brown. On the contrary, the ventral area is white. The muzzle or rostrum has an asymmetrical coloration. The right side is light, while the left is dark.

On the lower right jaw there is a light gray or white patch. Often this extends dorsally and laterally towards the upper jaw, reaching to the rear of the orifices.

On the other hand, it has two dark lines, which originate from the eye and the ear hole. One of these widens towards the anterior dorsal area, forming a large dark area.

State of conservation

Fin whale populations have been showing a progressive decline, due to various factors that affect them.

This situation, which occurs throughout the distribution of the mammal, puts the survival of this species at high risk. Because of this, the IUCN has categorized Balaenoptera physalus as a cetacean vulnerable to extinction.

Threats

In the 20th century, commercial hunting of fin whales caused a significant decline in their communities. This led to the enactment of protective measures, so that as of 1990 their captures ceased.

Although some hunting events have occurred sporadically, it currently seems unlikely that the figures will return to the high percentages of the past.

One of the threats of this species is the collision with large ships. The researchers point to the concern of these shocks when they occur in the waters of the Mediterranean. This is due to the fact that this area has a high population density of the cetacean during the summer.

In addition, fin whales tend to become entangled in nets, pots and meshes used in various commercial fishing gear. On the other hand, experts point out that the noise produced by military sonars, ships and radars can affect their reproduction.

The sound waves emitted by such equipment could interrupt the signal sent by males to females, thus interfering with their mating.

Actions

Balaenoptera physalus is included in Appendix I of CITES, except those that live in Norway, Iceland and Japan. It is also listed in Appendices I and II of the Convention on the Management of Migratory Species. On the other hand, this species is protected by the Agreement for the Conservation of Cetaceans in the Mediterranean and Black Seas.

Habitat and distribution

The fin whale is distributed worldwide, mainly in the coastal waters of the subpolar and temperate regions. Although it can be considered absent or infrequent in the tropics, in the 20th century they existed in Ecuador, Peru and the Gulf of New Guinea. At present, it has been sighted in Peru.

Some species are migratory, moving to colder waters during the summer and spring to feed. In the fall, they return to the tropical or temperate oceans.

On the contrary, other populations show sedentary habits, thus remaining in the same area throughout the year. This last group is generally found in the Gulf of California and the Mediterranean Sea.

The fin whale usually lives both in coastal platform waters and in the open sea, at depths of no less than 200 meters. During the summer, the habitat is strongly associated with dense populations of their favorite prey, such as krill, squid, and Atlantic herring (Clupea harengus).

Feeding

Balaenoptera physalus is a generalist feeder that feeds mainly on crustaceans and squid, including krill and some copepods.

Also, you can include in your diet a wide variety of fish, among which are the sand eel (Ammodytes americanus) and some species of the genera Clupea, Engraulis, Theragra and Mallotus.

Filter feeding

In filter feeding, this cetacean opens its mouth, while swimming at 11 km / h. In this way it gobbles up up to 18,000 US gallons of water. Then it closes its jaws, using the tongue and throat to push out the water that entered the oral cavity.

When the water comes out through the barbs, which causes fish and crustaceans to get trapped in them. Each drink could provide around 10 kilograms of food. Because fin whales consume up to 1,800 kilograms daily, it spends around three hours a day feeding.

In the event that its prey populations are not dense enough, or are too deep, this cetacean uses other hunting techniques. One of these is to swim at high speed and go around schools of fish. Thus, once all are agglomerated, the fin whale turns and devours the mass of fish.

Reproduction

Sexual maturity occurs between 4 and 8 years. In general, the male can mate when he is around 18.6 meters tall, while the female reproduces at a body length of about 19.9 meters.

Mating takes place during winter, in low latitude temperate seas. At this time, the fin whale forms a monogamous pair. During courtship, the male chases the female, while emitting vocalizations, which he repeats at a low frequency.

As for gestation, it lasts between 11 and 12 months. The calf is born measuring 6 meters and weighs 3,500 to 3,600 kilograms. The female suckles the young for 6 to 7 months. After this, the juvenile travels with the mother to the feeding area. In this he learns to capture the prey, allowing his independence from the mother.

References

1. Cooke, JG (2018). Balaenoptera physalus. The IUCN Red List of Threatened Species 2018. Recovered from iucnredlist.org.
2. NOAA Fisheries (2019). End whale. Recovered from fisheries.noaa.gov.
3. EDGE (2019). End whale. Recovered from edgaofexistence.org.
4. Peter Rudolph, Chris Smeenk, (2009). Indo-West Pacific Marine Mammals. Recovered from sciencedirect.com
5. Wikipedia (2019). End whale. Recovered from en.wikipedia.org.
6. Mahalingam, P. and M. Silberstein (2010). Balaenoptera physalus. Animal Diversity Web Retrieved from animaldiversity.org.