Giant bottle-nosed whale, North Pacific bottlenose whale, Northern four-toothed whale, Berardius, Four-toothed whales, Giant beaked whales
Four-toothed whales or giant beaked whales are beaked whales in the genus Berardius. They include Arnoux's beaked whale (Berardius arnuxii ) in cold Southern Hemisphere waters, and Baird's beaked whale (Berardius bairdii ) in the cold temperate waters of the North Pacific. A third species, Sato's beaked whale (Berardius minimus ), was distinguished from B. bairdii in the 2010s.Show More
Arnoux's and Baird's beaked whales are so similar that researchers have debated whether or not they are simply two populations of the same species. However, genetic evidence and their wide geographical separation has led them to be classified as separate. Lifespan estimates, based on earwax plug samples, indicate male whales can live up to 85 years, while females can have a lifespan of 54 years. It is estimated that the length at birth is ~4m. Growing up to ~10m, these are the largest whales belonging to the family Ziphiidae. Sato's beaked whale is much smaller, with adult males having a length of ~7m.
While Berardius arnuxii and Berardius bairdii are considered least concern by the IUCN. Berardius minimus is labeled as near threatened as of 2020.
This article currently largely treats four-toothed whales as monospecific, due to a lack of species-specific information.Show Less
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Baird’s beaked whales are deep-diving cetaceans which belong to a group called the ‘beaked whales’, named for their elongated beaks. These whales are among the least studied and most mysterious of all cetacean families. As the name suggest, they have a very long prominent beak, even by beaked whale standards. The lower jaw is longer than the upper and the front teeth are visible even when the mouth is fully closed, forming so called ‘battle teeth’. Their upperparts are dark brown, with a lighter mottled underside of unevenly spread white patches. They have a small dorsal fin located two thirds down the body, a blowhole that is crescent shaped, and a forehead with a melon-like shape, from where its slender beak projects.
Baird’s beaked whale is found in the east from the southern part of the Gulf of California, to the Bering, Japanese and Okhotsk Seas in the west and in the temperate North Pacific. They prefer deep ocean waters of 1,000 - 3,000 meters, where most of their prey can be found.
Baird’s beaked whales travel in breeding groups numbering 6-30 members. These groups are led by a large male whale. The scars on these leaders' beaks and backs indicate aggression and rivalry for such a position. They usually come to the water's surface 3-4 times at intervals of 10 -20 seconds before making a deep dive for at least 20 minutes. They can stay underwater for more than an hour. Their blow is difficult to see, being low and bushy. When a whale blows, its melon and beak tends to project just above the surface of the water. They are quite elusive and keep out of the way of ships, though sometimes they bask at the surface, unless startled.
There is no precise data about this whale’s mating system, but they occur in groups with a number of males, and in large groups with both male and female adults. Males may fight to access fertile females, making use of their distinctive ‘battle teeth’. Mid-summer is the time for mating, which occurs in the warm waters near California and Japan. The gestation period is probably around 12 months, though they have been reported up to 17 months, and a single calf is born. Births occur from late November until early May. Each mother will usually give birth to a calf every three years. Females reach sexual maturity around 10 to 15 years old and males around 30 years.
The Japanese fishing industry is responsible for around 70 whale deaths annually for their meat. Noise and chemical pollution are further threats, as well as climate change, as it is predicted to change the marine environment.
According to Wikipedia, estimates for Baird's are of the order of 30,000 individuals. According to the IUCN Red List, there are 1,100 Baird’s beaked whales in the eastern North Pacific, and about 7,000 individuals in Japanese waters (5,029 off the Pacific coast, 1,260 in the eastern Sea of Japan, and 660 for the southern Okhotsk Sea). Currently Baird’s beaked whales are classified as Data Deficient (DD) on the list of threatened species.