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Stejneger's Beaked Whale (Mesoplodon stejnegeri)

Status | Species Description | Habitat | Distribution | Population Trends | Threats | Conservation Efforts | Regulatory Overview | Taxonomy | Key Documents | More Info

Status

MMPA -  are protected under the MMPA.
CITES Appendix II - throughout its range

Species Description

Weight:
up to 3,520 pounds (1,600 kg)
Length:
18.5 feet (5.7 m)
Appearance:
coloration varies from dark gray to brownish and black, males have a pair of large, visible, forward-pointing tusk-like teeth that erupt from the arched lower jaw.
Lifespan:
estimated to be at least 36 years
Diet:
small deep-water fish, tunicates, and cephalopods (e.g., squid) of the families Gonatidae and Cranchiidae in deep "mesopelagic" and "bathypelagic" waters
Behavior:
Like most beaked whales, this species is difficult to approach and generally avoids vessels. It can be found singly or in small, tight social groups averaging between 3-15 individuals. It can make long dives of 10-15min and may reach depths of 4,920ft (1,500 m).

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.

Habitat

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).

Distribution

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.

Population Trends

The most recent stock assessment reports with population estimates are available on our website.

Threats

Conservation Efforts

The International Union for Conservation of Nature and Natural Resources (IUCN's) Red List of Threatened Species This link is an external site. considers this species "Data Deficient" due to insufficient information on population status and trends.

Regulatory Overview

This species is protected under the Marine Mammal Protection Act of 1972 as amended.

Taxonomy

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Cetacea
Family: Ziphiidae
Genus: Mesoplodon
Species: stejnegeri

Key Documents

(All documents are in PDF format.)
Title Federal Register Date
Stock Assessment Reports n/a various

More Information

References:

Updated: January 15, 2015