Sowerby's beaked whale (Mesoplodon bidens) COSEWIC assessment and status report: chapter 2

COSEWIC Executive Summary

Sowerby’s beaked whale
Mesoplodon bidens

Species information

Sowerby’s beaked whale is a medium-sized (4.5-5.5 m) beaked whale (Family Ziphiidae). It is dark grey in colour with light speckling.

Distribution

Sowerby’s beaked whales are found only in the North Atlantic. Their distribution is poorly known as few at-sea sightings have been confirmed. From these limited data and stranding locations, they are considered to be the most northern North Atlantic species of Mesoplodon, ranging offshore from Cape Cod to Davis Strait in the western Atlantic, and from Norway to Spain in the eastern Atlantic. In the mid-Atlantic the species ranges from Iceland to the Azores and Madeira. A stranding in the Gulf of Mexico may be extralimital.

Habitat

This species is most often sighted in deep water, along the continental shelf edge and slope.

Biology

Little is known about the biology of Sowerby’s beaked whales. Their diet appears to be composed mainly of deep-water fish and squid. Although the data are inconclusive, length at sexual maturity for both sexes is approximately 4.7m. They appear to be social, often sighted in groups of 2-6 animals, and mass strandings have occurred.

Population sizes and trends

There are no estimates of population size. The rarity of sightings may indicate that the species is uncommon. Alternatively, it may simply reflect the fact that there has been little search effort in the appropriate areas and that sighting and identifying these whales is exceptionally difficult.

Limiting factors and threats

Sowerby’s beaked whales are likely threatened by intense underwater sounds, especially those associated with mid-frequency sonar and seismic surveys. They are also vulnerable to ship strikes and fishing gear entanglement.

Special significance of the species

Sowerby’s beaked whale is a member of one of the least known groups of large mammals (the Ziphiidae), and together with the northern bottlenose whale, likely has one of the largest ranges within Atlantic Canada of any ziphiid.

Existing protection and other status designations

Sowerby's beaked whale was assessed as 'Special Concern' by COSEWIC in 1989 and as 'Data Deficient' by IUCN in 1996.

COSEWIC History

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal-Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.

COSEWIC Mandate

The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC Membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non-government science members and the co-chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions

Wildlife Species
A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.
Extinct (X)
A wildlife species that no longer exists.
Extirpated (XT)
A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.
Endangered (E)
A wildlife species facing imminent extirpation or extinction.
Threatened (T)
A wildlife species likely to become endangered if limiting factors are not reversed.
Special Concern (SC)Footnotea
A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.
Not at Risk (NAR)Footnoteb
A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.
Data Deficient (DD)Footnotec
A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

 

Canadian Wildlife Service

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

 

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