Mammal Species of the World
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- Original description: True, F.W., 1885. Contributions to the history of the Commander Islands. No. 5-Description of a new species of Mesoplodon, M. Stejnegeri, obtained by Dr. Leonard Stejneger, in Bering Island, 8:585. Proceedings of theU.S. National Museum, 8:584-585.
Stejneger's beaked whales, sometimes known as the "Bering Sea beaked whale" or the "Saber-toothed whale," are little known members of the beaked whale family (Ziphiidae). As adults, Stejneger's beaked whales can reach lengths of about 18.5 ft (5.7 m) and weigh up to 3,520 lbs (1,600 kg). Females may be slightly larger than males. Males can be easily distinguished from females and juveniles by a pair of large, visible, forward-pointing tusk-like teeth that erupt from the arched lower jaw. Females and juveniles have teeth as well, but they remain hidden beneath the gum tissue of the mouth, and their jawline is generally less-curved. This species of beaked whale is difficult to observe and identify at sea due to a low profile at the surface and a small inconspicuous blow.
Stejneger's beaked whales have a relatively medium-sized, round body with a small wide-based, slightly "falcate" dorsal fin located far down (about two-thirds) the animal's back. The whale's head has a low sloping forehead and indistinct melon. Their coloration varies from dark gray to brownish and black. There is a dark cap that extends across the top of the head from eye to eye and the lower jaw is usually white or pale gray. The skin may be covered with linear and oval-shaped scars and other markings. Individuals, especially mature males, accumulate more scars and scratches with age. Mature males often will battle one another for access to females.
Stejneger's beaked whales are usually found singly or in small, tight social groups averaging between 3-15 individuals. These groups may contain animals of mixed sexes, ages and life stages, or can be segregated. Like most beaked whales, this species is difficult to approach and generally avoids vessels.
Stejneger's beaked whales usually make 5-6 shallow dives followed by a longer dive that lasts 10-15 minutes and may reach depths of 4,920 ft (1,500 m) (Shirihai and Jarrett 2006). While diving, they use suction to feed on small deep-water fish, tunicates, and cephalopods (e.g., squid) of the families Gonatidae and Cranchiidae in deep "mesopelagic" and "bathypelagic" waters.
Stejneger's beaked whales may become sexual mature when they reach about 14.8 ft (4.5 m) in length. A sexually mature female will give birth to a single calf that is about 7.5-8 ft (2.3-2.5 m) long and weighs about 175 lbs (80 kg). The calving season is generally between spring and autumn. The estimated lifespan of this species is at least 36 years.
Many species of beaked whales (especially those in the genus Mesoplodon) are very difficult to distinguish from one another (even when dead). At sea, they are challenging to observe and identify to the species level due to their cryptic, skittish behavior, a low profile, and a small, inconspicuous blow at the waters surface; therefore, much of the available characterization for beaked whales is to genus level only. Uncertainty regarding species identification of beaked whales often exists because of a lack of easily discernable or distinct physical characteristics.
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Unknown
Regularity: Regularly occurring
Type of Residency: Year-round
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 from the Bering Sea to California and Japan, inhabiting only the cool temperate waters of the Northern Pacific Ocean.
Biogeographic Regions: pacific ocean (Native )
- Nowak, R. 1999. Walker's Mammals of the World, 6th Edition. Baltimore and London: The Johns Hopkins University Press.
Distributed throughout the cold temperate and subarctic waters of the North Pacific. On the eastern side of the North Pacific its distribution ranges from Saint Paul Island to southern California, with a majority of stranding records reported from the Alaskan coastlines. In the west it ranges from the Commander Islands to Japan. The center of its distribution seems to be the Aleutian Islands, where it has been known to strand in small groups. It is more likely that that this species frequents the Aleutian Basin and the Aleutian Trench rather than the shallow waters of the northern or eastern Bering Sea. Presence of Isistius scars suggests its movements are not restricted to cold temperate waters, but include temperate waters of North Pacific latitudes 38oN and lower where the Isistius populations are at greatest abundance.
Stejneger's beaked whales have a distribution throughout the North Pacific that includes California, the Aleutian Islands, southwest Bering Sea, Kamchatka, Okhotsk Sea, and the Sea of Japan. Strandings of this species have commonly occurred in the Aleutian Islands of Alaska and on the west coasts of Japan. Scientists speculate that this species may migrate north in the summer (Jefferson et al. 2008). Information on the distribution of these whales mostly comes from stranding records.
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
- Ridgway, S., S. Harrison. 1989. Handbook of Marine Mammals, Volume 4: River Dolphins and the Larger Toothed Whales. New York: Academic Press.
A single pair of teeth is positioned immediately ahead of the apex of the arch on the mouthline and are inclined anteriorly.
In adult males, nearly all the tooth that erupts from the lower jaw is exposed above the gumline. Teeth do not erupt above the gumline in females or juveniles.
The anterior edge of the tooth is longer than the posterior.
Diagnostic features of the skull and mandible
On the vertex of the dorsal skull the premaxillary bone extends forward of the nasal and frontal bones. Separates from Berardius and Ziphius.
A sulcus (groove) running along the middle of the combined surfaces of the nasal bones so depresses their combined middle that it is the lateral portion of each nasal bone that reaches farthest forward on the vertex. Separates from Tasmacetus and Indopacetus.
When the skull is upright and the long axis of the anterior half of the beak is horizontal, a horizontal plane transecting the summit of either maxillary prominence transects the mesethmoid bone. Separates from Hyperoodon.
Tooth alveoli of mandible are posterior to the mandibular symphysis. Separates from Berardius, Ziphius, Tasmacetus, Indopacetus, Hyperoodon, M. bowdoini, M. bidens, M. carlhubbsi, M. grayi, M. europaeus, M. hectori, M. layardii, M. mirus, M. perrini, and M. traversii.
Right premaxilla extends posteriorly beyond the right nasal a distance exceeding 70% of dorsal length of right nasal. Separates from M. ginkgodens.
Antorbital notches form obtuse angles. Separates from M. peruvianus.
A transverse plane perpendicular to the long axis of the rostrum and transecting the apex of the left antorbital notch, very nearly also transects the anterior most point reached by the pterygoid sinus. Separates from M. densirostris.
The melon is flattened compared to other Mesoplodon species. The melon slopes smoothly onto the medium length beak. The mouthline curves upward posteriorly, forming a prominent arch.
Males are gray to black over a majority of their bodies. The head has a prominent black cap on dorsal surface encompassing the blowhole and converging laterally to encompass the eye. The flipper pocket is also darker than surrounding skin. Females and juveniles are dark brownish-grey dorsally with lateral areas grading to a much lighter ventral coloration. The head has a prominent black cap on dorsal surface encompassing the blowhole and converging laterally to encompass the eye. The flipper pocket is also darker than surrounding skin.
The ventral surface of the flukes may exhibit concentric, striations that radiate out laterally from insertion of caudal peduncle. These striations can vary from light gray to white. Diffuse mottling or spotted pigmentation may occur on the ventral body surface from the throat region to the caudal peduncle. These markings are consistent with scars caused by Penella sp. and / or the cookie cutter shark, Isistius brasiliensis. Penella sp. causes small 1-2 cm diameter punctate scars, while Isistius bites lightly pigmented circular to oval shaped scars 4-8 cm in diameter. Isistius scars are generally concentrated on the posterior half of body.
Adult body length ranges between 5 to 6 m. Recorded maximum body length for adult males and females is 6.0 m and 5.4 m, respectively. Body length at birth is 2.2 m.
Most Likely Confused With:
Length: 500 cm
Size in North America
Range: up to 5.3 m
Catalog Number: USNM A21112
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Mammals
Collector(s): L. Stejneger
Year Collected: 1883
Locality: Bering Island, Commander Islands, Kamchatka, Russia, Bering Sea, Asia, North Pacific Ocean
- Type: True, F. W. 1885. Proceedings of the United States National Museum. 8: 584-585.
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).
- UNESCO-IOC Register of Marine Organisms
Habitat and Ecology
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
- Loughlin, T., M. Perez. 13 December 1985. Mesoplodon stejnegeri. Mammalian Species, No. 250: pp. 1-6.
Stejneger's beaked whales prefer the cold temperate and subarctic waters of the North Pacific Ocean. They are generally found in deep, offshore waters from 2,500-5,000 ft (750-1,500 m), on or beyond the continental slope (Reeves et al. 2002).
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.
Comments: Diet includes squid.
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 )
Has been observed in groups of up to 15 individuals of various sizes (IUCN 1991).
Life History and Behavior
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)
- Loughlin, T., M. Perez. 13 December 1985. Mesoplodon stejnegeri. Mammalian Species, No. 250: pp. 1-6.
Molecular Biology and Genetics
Barcode data: Mesoplodon stejnegeri
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.
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Download FASTA File
Statistics of barcoding coverage: Mesoplodon stejnegeri
Public Records: 3
Specimens with Barcodes: 3
Species With Barcodes: 1
National NatureServe Conservation Status
Rounded National Status Rank: NU - Unrankable
Rounded National Status Rank: N2 - Imperiled
NatureServe Conservation Status
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.
IUCN Red List Assessment
Red List Category
Red List Criteria
- 1996Data Deficient
- 1994Insufficiently 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
For management purposes, Stejneger's beaked whales inhabiting U.S. waters have been placed in the Alaska Stock and California/Oregon/Washington Stock. The estimated population for Mesoplodon spp. (Blainville's, Perrin's, Pygmy, Gingko-toothed, Hubb's, and Stejneger's beaked whales) in the California/Oregon/Washington stock is 575-1,000 animals. No current population estimates are available for this species of beaked whale and the status of the stocks is unknown. Scientists suggest that resident populations of this species may inhabit the southern Okhotsk Sea and the Sea of Japan. There are insufficient data to determine population trends for this species.
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).
In the past, some individuals were taken in the Japanese salmon driftnet fishery in the Sea of Japan and in driftnets off the west coast of North America. Entanglement in fishing gear, especially gillnets in deep water, is probably the most significant threat.
This species, like other beaked whales, is likely to be vulnerable to loud anthropogenic sounds, such as those generated by navy sonar and seismic exploration (Cox et al. 2006).
As a cold water species, Stejnegerâs beaked whale may be vulnerable to the effects of climate change as ocean warming may result in a contraction of the species range as it tracks the occurrence of its preferred water temperatures (Learmonth et al. 2006). The effect of such changes in range size on this species is unknown.
Evidence from stranded individuals of several similar species indicates that they have swallowed discarded plastic items, which may eventually lead to death (e.g. Scott et al. 2001); this species may also be at risk.
Incidental take/ bycatch in the driftnet and gillnet fisheries in the Sea of Japan and off the west coast of North America
Hunted in a Japanese fishery targeting beaked whales
Marine debris, they are known to have ingested dangerous items such as plastic bags and string (Jefferson et al. 2008)
Underwater sounds and anthropogenic noise may be harmful
Relevance to Humans and Ecosystems
Economic Importance for Humans: Positive
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
IUCN Red List Category
- IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
Stejneger's beaked whale
Stejneger's Beaked Whale (Mesoplodon stejnegeri), sometimes known as the Bering Sea Beaked Whale or the Saber-toothed Whale is a poorly-known member of the genus Mesoplodon. Leonhard Hess Stejneger initially described the species in 1885 from a skull, and nothing more of the species was known for nearly a century. The late 1970s saw several strandings, but it was not until 1994 that the external appearance was described from fresh specimens. The most noteworthy characteristic of the males is the very large, saber-like teeth, hence the name.
The body for this species is rather typical for a Mesoplodont, long and tapering at both ends. The beak of the whale is of medium length, and the mouthline forms an arch, though much smoother than other species. The teeth of the males are much larger than those of most other Mesoplodonts and point forwards and inwards right in front of the apex. Only Layard's beaked whale and the Spade Toothed Whale have longer teeth. The coloration is overall dark gray to black on the body with light coloration below, and around the head giving it a "helmeted" appearance. The coloration darkens with age, but females have a light pattern on the bottom of the flukes which become more apparent with age. Like most species, scars occur on the males (from other males) and cookie cutter shark bites are present on both sexes. The length is at least 5.25 meters (17 feet 6 inches) for males and 5.5 meters (18 feet) for females. They are likely around 2.1 to 2.3 meters long (7 to 8 feet) when born.
Population and distribution
This is the northernmost species of Beaked Whale in the Pacific Ocean, ranging up into the Bering Sea. They are distributed along both sides of the Pacific to Miyagi Prefecture, Japan and Monterey, California. They may migrate south in winter. As with most species of beaked whales, no population estimates have been made.
The whales are typically found in groups of 3 to 4 and sometimes up to 15 animals in a very close group. The groups may have age and sex segregation. Adult males fight each other extensively, and some specimens have been found with healed jaw fractures.
This species has been occasionally hunted in Japan in the past, and occasionally been caught in driftnets. It is uncertain how much this affects the population.
- ^ Taylor, B.L., Baird, R., Barlow, J., Dawson, S.M., Ford, J., Mead, J.G., Notarbartolo di Sciara, G., Wade, P. & Pitman, R.L. (2008). Mesoplodon stejnegeri. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 24 March 2009. Database entry includes a brief justification of why this species is of data deficient.
Did you know?
• Stejneger's beaked whales receive their common and scientific name from Leonhard Stejneger, who was a naturalist and curator at the Smithsonian Institution, after he described the species from a single skull discovered on Bering Island in 1885 (Reeves et al. 2002).
• Male Stejneger's beaked whale's have an unusually shaped lower jaw and huge tusk-like teeth.
Names and Taxonomy
Comments: Jones et al. (1992), Rice (1998), and Mead and Brownell (in Wilson and Reeder 1993, 2005) recognized M. carlhubbsi, M. bowdoini, and M. stejnegeri as separate species.