Sowerby's beaked whale (Mesoplodon bidens) COSEWIC assessment and status report: chapter 6

Biology

Little is known about the biology and life history of Sowerby’s beaked whale.

Life cycle and reproduction

Although the timing and age of breeding are unknown, females 483 cm and 505 cm long were sexually mature while a 462 cm female was not. Data concerning male sexual maturity are even more sparse. Males less than 500 cm long are considered immature based on necropsy data (Lien and Barry 1990). However, a study of skull morphology indicated that in the eastern Atlantic 470 cm males had attributes of sexual maturity (MacLeod and Herman 2004).

Behaviour

The social structure is also largely unknown. Almost all sightings in Canadian waters have been of groups of three to ten animals, and two mass strandings have been documented (Table 1). Sowerby’s beaked whales are presumed to be deep divers (Mead 2002). Like most other beaked whales, they probably avoid powered vessels (Mead 2002).  However, during several recent sightings off Scotland individuals approached the survey vessel (C.D. MacLeod pers. comm. 2004).

Predation

There are no data on predation on Sowerby’s beaked whales. Killer whales (Orcinus orca) and large sharks are their only likely predators.

Feeding ecology

Based on stomach contents and stable isotope analysis of stranded animals, mid- to deepwater fish and offshore squid appear to comprise the bulk of the diet of Sowerby’s beaked whales (MacLeod et al. 2003; Ostrom et al. 1993).

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