Blainville’s Beaked Whale, Mesoplodon densirostris

Blainville’s beaked whale (Mesoplodon densirostris), also known as the dense-beaked whale, can be found in a large range that includes the warm and tropical waters of all oceans. It prefers to reside at depths between 1,600 and 3,000 feet and does not migrate. This species received its common name from Blainville, the man who classified it as Delphinus densirostris after studying a description of a piece of one individual’s nose located in the Paris Museum. In 1846, John Edward Gray studied a complete skull, which was sent by M. Leduc from Seychelles in 1839, and named the species Ziphius seychellensis. Its classification changed again when a French scientist named Paul Gervais placed the whale the Dioplodon genus, which means two-toothed.

Blainville’s beaked whale varies in size depending upon the sex. Males reach an average body length of about 14 feet with an average weight of 1,800 pounds, while females are larger, reaching an average body length of about 15 feet with a weight of 2,200 pounds. Although this species’ body is stout, it is shorter than other species within its genus. Males can be distinguished from females by their overarching rostrum, which slopes down into a beak that encloses a tooth covered in barnacles. Both males and females are distinct in that the bones located in the rostrum are denser than in other species, but the purpose of this bone is not yet known. This whale is dark bluish grey on the dorsal area and grey on the underbelly, while the head is typically brownish in color.

Blainville’s whale is sociable, gathering in small groups of up to seven individuals. Average dives have been recorded to last twenty-two minutes, and this species becomes silent after reaching a depth of about 557 feet, most likely to avoid encounters with orcas. It is thought that the diet of this species consists mainly of squid, which is supported by one study conducted on the stomach contents of an individual that showed only squid.

Although Blainville’s whale is common throughout its range, its total population numbers are not known. This species has never been threatened by whaling, but a small amount of hunting has occurred. It is protected by the ACCOBAMS and the ASCOBANS and appears in the Western African Aquatic Mammals MoU, as well as the Pacific Cetaceans MoU. More research is needed to better understand the species as a whole and its threats, so it appears on the IUCN Red List with a conservation status of “Data Deficient.”

Image Caption: Blainville’s beaked whale (Mesoplodon densirostris). Credit: NOAA Photo Library/Wikipedia (CC BY 2.0)