Mesoplodon stejnegeri True,
English: Stejneger's beaked whale
Spanish: Zifio de Stejneger, ballena picuda de Stejneger
French: Mésoplodon de Stejneger, baleine à bec de
Mesoplodon stejnegeri © Wurtz-Artescienza
Stejneger's beaked whale appears to be dark above and pale below,
with the beak and neck areas being paler. However, a dark cap extending
from both eyes over the top of the head appears to be characteristic.
In adult males two large erupted teeth point forwards near the peak
of the arched lower jaw, about halfway from the gape . The largest
male measured 5.7 m and 1,600 kg (Jefferson et al. 2008). Females
and young males have no erupted teeth and, at sea, are probably
impossible to distinguish from other Mesoplodon species (Carwardine,
Stejneger's beaked whale ranges in subarctic waters of the North
Pacific from the Bering Sea south to Japan and central California
(Loughlin and Perez, 1985; Rice, 1998). The center of its distribution
seems to be the Aleutian Islands, where M. stejnegeri has been known
to strand in small groups. There are also sighting records from
the central Aleutian Islands (Mead, 1989 and references therein).
Distribution of Mesoplodon stejnegeri (Taylor
et al. 2008; © IUCN; enlarge
map). It lives over
continental slopes and in oceanic waters of the sub-Arctic and temperate
North Pacific from
California to Japan (Pitman, 2002).
3. Population size
4. Biology and Behaviour
Schooling: Small groups sometimes travel abreast, almost
touching one another, and may surface and submerge in unison. There
are reports of 5 or 6 shallow dives, followed by long dives of 10
to 15 minutes. Diving involves a slow, casual roll at the surface.
Groups usually include both small and large animals, suggesting
a mixing of ages and/or sexes (Carwardine, 1995).
Walker and Hanson (1999) also concluded that Stejneger's beaked
whales travel in small groups, as 4 animals stranded within short
range of one another at Kuluk Bay, Adak Island (51°54'N, 176°34'W)
in August 1994.
Food: Stejneger's beaked whales feed on squid of the family
Gonatidae and Cranchiidae in mesopelagic and bathypelagic depths.
Fish are also taken (Walker and Hanson, 1999; Jefferson et al. 2008).
There have been numerous strandings from the coasts of Japan with
the Sea of Japan, and many fewer along the Pacific coast. The large
peak in strandings in this area in winter and spring suggests that
the species may migrate north in summer (Mead, 1989). M. stejnegeri
in the Bering Sea sometimes bear fresh cookie-cutter shark bites,
also suggesting that they probably moved north from warmer waters
Entanglement in fishing gear, especially gillnets in deep water,
is probably the most significant threat (Taylor et al. 2008). Several
Stejneger's beaked whales are known to have been taken in salmon
driftnets off Japan and on the west coast of North America. There
have been occasional direct catches of this species off Japan and
possibly elsewhere (Jefferson et al. 1993).
Baker et al. (2006) report on whale meat from M. stejnegeri
found in a systematic survey of whalemeat markets in South Korea
between 2003 and 2005. The meat originated presumably from by-catch.
Honma et al. (1999) report on one specimen having died after a strike
from a jetfoil operating for the Sado Line (Niigata-Ryotsu route)
in the Sea of Japan.
Range states (Loughlin and Perez, 1985 ; Taylor et al. 2008) :
Canada; Japan; Russian Federation; United States of America
IUCN status: "Data Deficient". Not listed by CMS. Listed
in Appendix II of CITES.
8. Sources and further information
Mesoplodon - Beaked whales: Introduction and Sources"
© Boris Culik (2010) Odontocetes.
The toothed whales: "Mesoplodon stejnegeri". UNEP/CMS
Secretariat, Bonn, Germany. http://www.cms.int/reports/small_cetaceans/index.htm
© Illustrations by Maurizio Würtz, Artescienza.
© Maps by IUCN.