Mesoplodon stejnegeri, True, 1885

Russell A. Mittermeier & Don E. Wilson, 2014, Ziphiidae, Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona: Lynx Edicions, pp. 326-357 : 351-352

9.

Stejneger’s Beaked Whale

Mesoplodon stejnegeri

French: Baleine-a-bec de Stejneger / German: Stejneger-Zweizahnwal / Spanish: Zifio de Stejneger

Other common names: Bering Sea Beaked Whale, Sabertoothed Beaked Whale

Taxonomy. Mesoplodon stejnegert True, 1885 ,

Russia, Commander Islands, “Bering Island.”

This species is monotypic.

Distribution. Endemic to cold temperate and subpolar waters of N Pacific Ocean, from the relatively shallow waters of the Bering Sea in the N to S Japan (W Pacific Ocean) and C California (E Pacific Ocean); itis the only species of Mesoplodon that commonly occurs in the Sea ofJapan.

Descriptive notes. Total length 480-574 cm; weight 1000-1300 kg. Body of Stejneger’s Beaked Whale is spindle-shaped, with greatest girth around its mid-point. Flukes are wide in relation to body length, and tailstock is compressed laterally. Dorsal fin is small and set approximately two-thirds the distance between tip of the beak and end of the tail. Males and females are uniformly gray to black. Adult male Stejneger’s Beaked Whales may have a number of long white lines that are unpigmented scars from aggressing male—male interactions. Rostrum and lowerjaw form a short, indistinct beak, and there are two grooves on the throat. Lowerjaw of adult males is arched, and a pair of triangular tusks is found midway alongit.

Habitat. Primarily waters deeper than 200 m, and like other species of Mesoplodon , Stejneger’s Beaked Whale may preferentially occur over areas of complex seabed topography, butits habitat preferences have not been studied in detail.

Food and Feeding. Stejneger’s Beaked Whale primarily consumes species of deep-water squid. As with other species of beaked whales, Stejneger’s Beaked Whale islikely to forage at depths greater than 500 m for much ofits life.

Breeding. There is no information available for this species.

Activity patterns. There is no information available forthis species.

Movements, Home range and Social organization. There is nospecific information available for this species, but Stejneger’s Beaked Whales are known to occur in small groups offive or fewer individuals. The typical composition of these groups remains unclear.

Status and Conservation. CITES Appendix II. Classified as Data Deficient on The [UCN Red List. There are no estimates of global population size of Stejneger’s Beaked Whale. It may be one of the more common species of Mesoplodon in some parts of its distribution, such as around the Aleutian Islands and in the Sea ofJapan. Like other species of beaked whales, Stejneger’s Beaked Whale is potentially affected by ingestion of plastic debris, bycatch in driftnet fisheries, and noise pollution. As a cool-water species, it may also be affected by climate change. Nevertheless, nothing is known about the form or extent of these potential impacts.

Bibliography. Loughlin et al. (1982), MacLeod et al. (2006), Mead (1989b), Rice (1998), Walker & Hanson (1999).

Figures

1. Baird’s Beaked Whale (Berardius baiwrdu), 2. Arnoux’s Beaked Whale (Berardius arnuxu), 3. Cuvier’s Beaked Whale (Ziphius cavirostris), 4. Northern Bottlenose Whale (Hyperoodon ampullatus), 5. Southern Bottlenose Whale (Hyperoodon planifrons), 6. Shepherd’s Beaked Whale (Tasmacetus shepherd), 7. Longman’s Beaked Whale (Indopacetus pacificus), 8. Hubbs’s Beaked Whale (Mesoplodon carlhubbsi), 9. Stejneger’s Beaked Whale (Mesoplodon stejnegeri), 10. Pygmy Beaked Whale (Mesoplodon peruvianus), 11. Perrin’s Beaked Whale (Mesoplodon perrini), 12. True’s Beaked Whale (Mesoplodon marus), 13. Strap-toothed Whale (Mesoplodon layardii), 14. Hector’s Beaked Whale (Mesoplodon hectori)

Distribution. Endemic to cold temperate and subpolar waters of N Pacific Ocean, from the relatively shallow waters of the Bering Sea in the N to S Japan (W Pacific Ocean) and C California (E Pacific Ocean); itis the only species of Mesoplodon that commonly occurs in the Sea ofJapan.