Sowerby's Beaked Whale

Description

The Sowerby’s beaked whale is a small- to medium-sized toothed whale of the family Ziphiidae.

An adult Sowerby’s beaked whale is typically 4.5-5.5 m long and dark grey in colour. They have a small head with a long, narrow beak and a small triangular dorsal fin approximately 2/3’s of the way back from the beak to flukes. Their tail flukes generally have no center notch, and they have relatively long pectoral fins.

Distribution & Population

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 shore stranding locations, they are considered to be the most northern North Atlantic species of the genus Mesoplodon (beaked whales), and range 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.

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.

Habitat

This species is most often sighted in deep water, along the continental shelf edge and slope. Sowerby’s beaked whales are only rarely seen in coastal waters.

Biology

Little is known about the biology of Sowerby’s beaked whales. They are considered deep divers and their diet appears to be composed mainly of deep-water fish and squid. Killer whales and large sharks are their only probable predators. Although the data are inconclusive, length at sexual maturity for both sexes is approximately 4.7m. They appear to be social, generally sighted in groups of 2-10 animals, and mass shore strandings have occurred.

Threats

There is evidence that beaked whales are vulnerable to human-created, under-water ‘noise pollution’, such as ship propellers, drilling, and explosions.

Some mass strandings of beaked whales have been associated with high energy, mid-frequency military sonar while behavioural and distribution changes have been observed in some whale species after seismic surveys (the use of compressed air guns to map the ocean floor). Seismic activities associated with oil and gas exploration off the coast of Atlantic Canada may therefore have an adverse effect on Sowerby’s beaked whale, although the likelihood, nature and severity of such an effect is poorly understood.

Sowerby’s beaked whales are also vulnerable to ship strikes, fishing gear entanglement, and toxins in the water.

Existing Protection and Other Status Designations

The Marine Mammal Regulations of the Fisheries Act prohibits the killing or disturbance of marine mammals, except where a licence has been issued to fish for a particular species. Currently there are no licences issued to fish for Sowerby’s beaked whales in Canadian waters. The Fisheries Act prohibits the harmful alteration, disruption or destruction of fish habitat, including marine mammal habitat, except where authorized by the minister.

In addition, the Government of Canada has designated the Gully (a large deep water canyon off the coast of Nova Scotia where Sowerby’s beaked whales have been sighted) as a Marine Protected Area (MPA) under the Oceans Act. Regulations for this MPA "prohibit the disturbance, damage, destruction or removal of any living marine organism or any part of its habitat within the MPA". Some oil and gas operators have also instituted their own "Codes of Practice" for the Gully in order to minimize operational impacts on whales.

Sowerby’s beaked whale is listed by the International Union for Conservation of Nature as ‘Data Deficient’ (IUCN 2004), and is listed in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES 2004).

References

COSEWIC 2006. COSEWIC assessment and update status report on the Sowerby’s beaked whale Mesoplodon bidens in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vi + 20 pp. (www.sararegistry.gc.ca/status/status_e.cfm).