Stejneger’s beaked whale  (Mesoplodon stejnegeri)

Stejneger's beaked whale is classified as Data Deficient (DD) on the IUCN Red List (1) and listed on Appendix II of CITES (2).

Named after Leonhard Stejneger, who discovered the species in 1885 (5), Stejneger’s beaked whale (Mesoplodon stejnegeri) is an elusive species which is rarely seen at sea (6). This could be due to its small population size, inconspicuousness nature, or because it is hard to discriminate from other species in its genus (7).

Stejneger’s beaked whale has a relatively small, sloping head and, as its name suggests, a long beak, or ‘rostrum’, at the end of its spindle-shaped body. It has small, maneuverable flippers and a hooked dorsal fin which sits quite far down along the back (7) (8).

The male Stejneger’s beaked whale is uniformly dark, while the female is darker on top and lighter underneath. Juveniles have light streaks around the face and neck (7). This species has a dark cap across the top of the head, between the eyes, and usually a white or pale grey lower jaw (3).

Adult male Stejneger’s beaked whales can also be distinguished by the presence of two large teeth, each of which protrudes from the side of the lower jaw (8). Males use these tusk-like teeth during competitive contests for females, resulting in long scars and scratches over much of the body (3) (7).

Adult Stejneger’s beaked whales also often have many circular white scars around the end of the body. These could be marks left by squid suckers, skin parasites, lampreys (Lampetra tridentata), or marks from collisions or fights (7).

Stejneger’s beaked whale is found throughout the North Pacific, including around southern California and the Aleutian Islands, to the Bering Sea and the Sea of Japan (1).

Stejneger’s beaked whale dwells mainly in sub-Arctic waters (1), which are about 750 to 1,500 metres deep (5).

Stejneger’s beaked whale is usually a solitary species, or may be found in small, tight social groups of around 3 to 15 individuals, which gently submerge and surface in synchrony (3) (9).

Squid are one of the favoured prey of Stejneger’s beaked whale (2), but it also feeds on small deep-water fish and tunicates (3). When feeding, Stejneger’s beaked whale typically makes several shallow dives, followed by a longer dive, which may last for up to 15 minutes (3). This species may dive to an incredible depth of 1,500 metres (3).

The female Stejneger’s beaked whale gives birth to a single calf at any time between spring and autumn. The young whale weighs around 80 kilograms at birth, and reaches sexual maturity at a body length of about 4.5 metres. Stejneger’s beaked whale may live for up to 36 years (3).

Strandings of Stejneger’s beaked whale are common in the Aleutian Islands and on the west coast of Japan, which has led to the conclusion that this species migrates north in the summer (10).

The primary threat to Stejneger’s beaked is entanglement in fishing gear. Although it is not directly targeted by fishermen, it may accidentally get caught in fishing nets (1).

Plastic waste may also be detrimental to Stejneger’s beaked whale when swallowed, as whales of similar species have been known to swallow discarded plastic (11). Like other beaked whales, Stejneger’s beaked whale is also affected by man-made noise, such as that created by navy sonar and seismic exploration (12).

Stejneger’s beaked whale may also be affected by climate change in future. As it follows a specific range of water temperatures, ocean warming my result in its distribution contracting (13).

Like all marine mammals, Stejneger’s beaked whale is protected under the 1972 Marine Mammal Protection Act in the United States, which means that hunting of this species is prohibited in U.S. waters (3).

Stejneger’s beaked whale is also listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), which means that international trade in this species should be carefully monitored to avoid overexploitation (4).

It has been recommended that further research is undertaken on Stejneger’s beaked whale, to determine the extent to which the species is being impacted by the numerous threats it faces, and to better inform any conservation measures (1).

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more about Stejneger’s beaked whale:

• NOAA Fisheries Office of Protected Resources – Stejneger’s Beaked Whale:
  http://www.nmfs.noaa.gov/pr/species/mammals/cetaceans/beakedwhale_stejnegers.htm
• Convention on Migratory Species - Mesoplodon stejnegeri:
  http://www.cms.int/reports/small_cetaceans/data/m_stejnegeri/m_stejnegeri.htm

Find out about the conservation of whales and dolphins:

• Whale and Dolphin Conservation Society:
  http://www.wdcs.org.uk/
• The Beaked Whale Resource:
  http://www.beakedwhaleresource.com/index.html