Balaenoptera physalus, Linnaeus, 1758

Identification

The fin whale is the second largest animal on Earth (after the Blue whale). A distinctive feature is the asymmetric pigmentation of the head, in which the right side is white (lower “lip”,mouth cavity and some baleen plates) and the left side is uniformly grey. The dorsal fin is small and tilted back. It has a longitudinal edge on the head. They feature a white-grey variable “insignia” on each side of the back of the head. They have 260-480 baleen plates, dark grey or black in colour, except in the first third of the right jaw, where they have a yellow or cream colour. The long, aerodynamic body has a silvery grey or dark grey colour on the back and a white colour on the lower area. The tail stock is thick and the flippers are relatively short, pointed and dark, but white on the inside. They have 50-100 throat grooves in the neck, ending normally behind the navel. It is rare to see the fluke, as well as the dorsal fin is rarely seen on the surface at the same time as the blowhole, when they emerge.
The blow appears as a column of splashes very high and narrow (4-6 meters high).

Biology

The calf is born with 2 tons and 6-6.5m. Adults can weigh between 30 and 80 tons and measure between 18-22m in length, and males are smaller than females. Females give birth in winter, probably in tropical and subtropical waters after an 11-12 month gestation period. Fin whales feed on krill and various species of small pelagic fish, swimming quickly towards clusters of prey.They usually migrate in the spring and autumn, alternating between breeding zones in the winter and feeding zones in the summer, where they can be seen in cold and polar temperate waters. Average life expectancy is at least 80 years.

Behavior

The fin whale jumps a few times, being typical to “land” on the belly, with a tremendous impact. They can also twist at half height and dive on a flank. It is usually indifferent in the presence of boats. The immersion movement depends on whether it moves slowly to the surface or emerges from a deep dive. It typically blows between 2 to 5 times, at intervals of 10 to 20 seconds, before diving for 5 to 15 minutes. Dives to depths of at least 230m. The way the whale swims on the right side while feeding it might be related to asymmetrical pigmentation. Fast swimmer, capable of reaching speeds over 30km/h. It is more commonly seen in small groups (3-7 individuals).

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