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Sowerby’s Beaked Whale (Mesoplodon bidens)

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Sowerby’s beaked whales, sometimes known as the “North Atlantic beaked whale,” are little known members of the beaked whale family (Ziphiidae). As adults, Sowerby’s beaked whales can reach estimated lengths of 14.5-21 feet (4.4-5.5 m) and weigh 2,200-2,900 pounds (1,000-1,318 kg). Males, which are generally larger, can be distinguished from females and juveniles by a pair of visible teeth that erupt from the slightly arched lower jaw. Females and juveniles have teeth as well, but the teeth remain hidden beneath the gum tissue of the mouth, and their jawline is straight. 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.

Sowerby’s beaked whales have a small to medium-sized body with a very long, slender beak relative to other mesoplodonts, as well as a bulge on the forehead area. The beak often emerges at a steep angle when surfacing. They have a small, wide-based, slightly “falcate” “dorsal” fin located far down (about two-thirds) the animal’s back. Most of the body has a charcoal gray coloration with a pale underside. The lower jaw is usually light gray or white. Calves are generally darker than adults. This species has less visible scarring than most other beaked whale species.

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.

Sowerby’s whales are usually found individually or in small, closely associated groups averaging between 3-10 individuals. Regular dives range from 10-15 minutes, but dives of at least 28 minutes reaching depths up to 4,920 feet (1,500 m) have been recorded. While diving, they use suction to feed on small fish (e.g., Atlantic cod) and cephalopods (e.g., squid) in deep waters.

Sowerby’s beaked whales may reach sexual maturity at about 7 years of age. Their breeding season may be from late winter to spring. A sexually mature female will give birth to a single newborn calf that is about 8-9 feet (2.4-2.7 m) long and weighs about 375 pounds (170 kg). The estimated lifespan of this species is unknown.

This species is classified as DATE INCOMPLETE according to the IUCN's Red List.
This species is classified as DATE INCOMPLETE according to the IUCN’s Red List.

Status

MMPA – Sowerby’s beaked whales, like all marine mammals, are protected under the MMPA.
CITES Appendix II – throughout its range

Species Description

Weight:
2,200-2,900 pounds (1,000-1,315 kg)
Length:
14.5-21 feet (4.5-5.5 m)
Appearance:
small to medium-sized charcoal gray body with a very long, slender beak and a bulge on the forehead area
Lifespan:
unknown, but sexually mature at around 7 years
Diet:
small fish like Atlantic cod and cephalopods like squid
Behavior:
they have a low profile at the surface and a small, inconspicuous blow, making them difficult to observe and identify at sea

RELATIVE SPECIES: True’s, Gervais, Blainville beaked whales.

OTHER NAMES: North Atlantic or North Sea Beaked Whale

NEIGHBORING SPECIES: Northern Bottlenose Whale, Blainville’s

THREATS: Entanglement in fishing gear.

DIET: Squid and Arctic Cod

MANNER OF FEEDING: Dive deep and suction small fish and squid

BEHAVIOR: Travel in groups of 8-10 closely related individuals, skittish and inconspicuous

REPRODUCTION: Become sexually mature at 7 years. Females have 1 calf.

LIFE SPAN: Unknown

Habitat

Sowerby’s beaked whales prefer the deep, cold temperate and subarctic waters of the North Atlantic Ocean, but have been reported near the ice pack as well.

Distribution

Sowerby’s beaked whales are distributed throughout the North Atlantic Ocean (30-71° North), which includes the Norwegian Sea, Labrador Sea, Iceland, Baltic Sea, and south to Massachusetts, Madeira, and the Canaries. Reports of this species in Canadian waters are considered rare. They are not known to occur in the Mediterranean Sea. Strandings have occurred in Florida and Italy, but these are considered outside their normal range. Their distribution may vary depending on the movements of oceanographic currents. There are no known seasonal movements or migrations for this species.

Population Trends

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

Threats

  • bycatch from fishing gear, such as driftnets and gillnets off the U.S. Atlantic coast
  • hunting, cetaceans are targeted in Newfoundland and by Norwegian whalers off of Iceland and in the Barents Sea
  • underwater sounds and anthropogenic noise, as anthropogenic noise levels in the world’s oceans are an increasing habitat concern, particularly for deep-diving cetaceans like Sowerby’s beaked whales that use sound to feed, communicate, and navigate in the ocean

Conservation Efforts

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

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: bidens

References:

  • Reeves, R. R., P. A. Folkens, et al. (2002). Guide to Marine Mammals of the World. New York, Alfred A. Knopf. p. 280-281.
  • NOAA

Cool/Gross/Weird:

  • Sowerby’s beaked whale was the first living species of beaked whale to be discovered.
  • Sowerby’s beaked whale’s scientific species name (bidens) is derived from the Latin word bifor “two” and dens for “teeth.”

-TSF-

 

 

 
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