Mesoplodon stejnegeri

"Thirty-one of the 48 sightings of Stejneger's beaked whale have come from Alaskan waters. It is suspected this species favors deep waters, including the Aleutian Trench and the Aleutian Basin, which is some 3,500 m deep, rather than the shallow waters of the Bering Sea. The whales were seen traveling in groups of 5-15; some individuals were large and some were small.  This species is also known as the sabre-toothed beaked whale, hinting at the shape of the adult male's teeth."

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Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Unknown

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Stejneger's beaked whales are found in continental slope and oceanic waters of the North Pacific Basin, from southern California, north to the Bering Sea, and south to the Sea of Japan (presumably including at least the southern Okhotsk Sea – Mead 1989; MacLeod et al. 2006). This appears to be primarily a cold temperate and sub-arctic species, and this is probably the only species of the genus common in Alaskan waters. It is most commonly stranded in Alaska, especially along the Aleutian Islands. Also, there have been a large number of strandings (at least 34) from along the Sea of Japan coast 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; Yamada 1997).

Mesoplodon stejnegeri ranges from the Bering Sea to California and Japan, inhabiting only the cool temperate waters of the Northern Pacific Ocean.

Biogeographic Regions: pacific ocean (Native )

North Pacific

occurs (regularly, as a native taxon) in multiple nations

Global Range: Cold temperate to subarctic North Pacific (based on stranding records); apparently distributed across much of the southern Bering Sea, south to the northern Sea of Japan and to Monterey, California; strandings are fairly common in the Aleutians (Leatherwood and Reeves 1983).

Mesoplodon stejnegeri ranges in length from 3 to 7 m, although they are generally longer than 5.3 m. Females are normally longer than males, and the crania of females are larger than those of males.

Both sexes are uniformly gray to black, with light pale countershading ventrally, although males tend to be more uniformly dark.

Mesoplodon stejnegeri is distinguished from other Mesoplodons by tooth shape and position. Members of this species have two large, exposed, tusk-like teeth on the lower jaw (Nowak 1999). These teeth are also distinctively larger in males.

Scarring, which is present on most M. stejnegeri, results from intraspecific fighting over mates, and is inflicted by the teeth while the mouth is closed (Ridgway and Harrison 1989).

Range length: 3 to 7 m.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: female larger; male more colorful; ornamentation

Length: 500 cm

Length:
Range: up to 5.3 m

Habitat and Ecology

Systems

• Marine

Stejneger's beaked whales, Mesoplodon stejnegeri, inhabit the deep waters of the ocean far from the shorelines. These animals are rarely seen at sea. They prefer a habitat with cool water. Mesoplodon stejnegeri has been observed living sympatrically with Hubb's beaked whales where the ranges of the two species overlap off the coast of northern Japan to Oregon and British Columbia.

Habitat Regions: temperate ; saltwater or marine

Aquatic Biomes: pelagic

cold temperate and subarctic, oceanic

Habitat Type: Marine

Comments: Has been observed in waters 730-1560 m deep on the steep slope of the continental shelf as it drops off into the Aleutian Basin (Loughlin et al., 1982, J. Mamm. 63:697-700).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Mesoplodon stejnegeri feeds primarily on deep-water squid. The diet includes both cephalopods and fish. A school of salmon was observed being chased by M. stejnegeri off the coast of Japan, and this species is sometimes trapped in salmon driftnets.

Animal Foods: fish; mollusks

Primary Diet: carnivore (Molluscivore )

Comments: Diet includes squid.

Has been observed in groups of up to 15 individuals of various sizes (IUCN 1991).

Nothing is known about the reproduction of M. stejnegeri, although it is speculated that litter size is one and parturition occurs in the spring and summer.

Range number of offspring: 1 (low) .

Average number of offspring: 1.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Although parental investment in this species has not been documented, because these animals are mammals we can infer that females provide a great deal of parental care. They are likely to provide their young with protection as well as food, in the form of milk, until the calves are able to care for themselves.

Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Protecting: Female)

The following is a representative barcode sequence, the centroid of all available sequences for this species.

There are 3 barcode sequences available from BOLD and GenBank.  Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.  See the BOLD taxonomy browser for more complete information about this specimen and other sequences.

Download FASTA File

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 3
Specimens with Barcodes: 3
Species With Barcodes: 1

Canada

Rounded National Status Rank: NU - Unrankable

United States

Rounded National Status Rank: N2 - Imperiled

Year Assessed

Assessor/s

Reviewer/s

Justification

History

• 1996
  Data Deficient
• 1994
  Insufficiently Known
  (Groombridge 1994)

These whales are a conservation concern. They are listed as Appendix II by CITES, and Data deficient by IUCN.

US Federal List: no special status

CITES: appendix ii

IUCN Red List of Threatened Species: data deficient

Rounded Global Status Rank: G3 - Vulnerable

Reasons: Occurs in cold temperate to subarctic North Pacific (based on stranding records); believed to be vulnerable to incidental take in gill nets, but there is little information available on the extent of such mortality.

Population

Population Trend

Major Threats

Comments: Believed to be vulnerable to incidental take in gill nets, but there is little information available on the extent of such mortality (IUCN 1991).

Conservation Actions

The meat of M. stejnegeri is considered palatable when cooked, but the Makah Indians of Washington reported cases of diarrhea after eating the blubber and flesh. Commercial fisheries, primarily in Japan, take a small number of M. stejnegeri yearly.

Positive Impacts: food

Data Deficient (DD)