Stejneger's beaked whale (Mesoplodon stejnegeri), also known as the Bering Sea beaked whale or the saber-toothed whale, is a relatively unknown member of the genus Mesoplodon inhabiting the North Pacific Ocean. Leonhard Hess Stejneger collected the type specimen (a beach-worn skull) on Bering Island in 1883, from which Frederick W. True provided the species' description in 1885. In 1904, the first complete skull (from an adult male that had stranded near Newport, Oregon) was collected, which confirmed the species' validity. Limited data exists regarding the global population of Stejneger's beaked whales, primarily due to the infrequency of sightings at sea. In general, beaked whales are elusive and wary, and the species within this family do not have prominent physical traits in comparison to other beaked whales. This makes it challenging to identify them individually.
Description
thumb|Head of an adult male, showing the characteristic dark cap and large teeth.
The body of this species is typical for the genus Mesoplodon, long and tapering at both ends. The snout is of medium length, and the mouthline forms an arch, though much smoother than in other species. This species is distinguishable from other Mesoplodon via tooth shape, which got them the name of saber-toothed whale, and position. The teeth of the males are much larger than those of most other Mesoplodon species, and point forwards and inwards right in front of the apex. Only strap-toothed whales and spade-toothed whales have longer teeth.
Their coloration ranges from grey to black with a light ventral side, though males are usually darker. The coloration darkens with age, but females also have a light pattern on the bottom of the flukes that becomes more apparent with age. Their length is at least for males and for females, and they can weigh up to 3,527 pounds.
Behavior and ecology
Social behavior
These whales are diurnal and migratory, typically found in pods of two to six, but some research shows they have been found in pods from as low as five to as many as fifteen. The groups may have age and sex segregation. They are very social animals and swim side by side, often making contact, surfacing and diving together. They can swim at speeds of 5,5 to 7,5 km/h, with top speeds reaching roughly 11 km/h. These vocalizations can be used for reproduction, danger alarms, or general communication between whales. All of their communication is tactile and chemical based and they have an average lifespan of 35 years old. In one instance, a school of salmon was seen being pursued by M. stejnegeri off the coast of Japan.
Additionally, as deep-diving cetaceans, these whales rely on sound for feeding, communication, and navigation. Noise pollution from human activities, such as active sonar or seismic surveys, can disrupt their natural behaviors and forced them to abandon critical habitats. In the United States, all Stejneger's beaked whales are protected under the Marine Mammal Protection Act. Efforts to conserve this species include reducing encounters with fishing gear and mitigating the impacts of vessel disturbances, noise pollution, and other human-related threats.