Mesoplodon bidens

Description: 

Sowerby’s beaked whale inhabits deep waters and is the species the most often recorded of the genus Mesoplodon even if it is rarely seen alive. It seems to inhabit a range somewhat north of the other species in its genus.

 

Physical description and behaviour:

Sowerby’s beaked whales have a slender tapering body, rather small and narrow flippers and a slender and small recurved dorsal fin located almost two-third along their back. Their body tends to be dark grey in colour and relatively long, as females measure around 5.1 m length and males 5.5 m. Males have a single pair of teeth extruding from the middle of their beak. The species’ head is small and like other beaked whales, they have a well-defined and long beak. They also tend to have a noticeable bulge in front of their blowhole.

Sowerby’s beaked whale is fairly uncommon and typically forms small groups rarely exceeding 10 individuals. It prefers deep water habitats of 700 m depth or more and is very rarely observed alive. They tend to come to the surface only briefly. The species’ diet seems to mainly consist of fish and occasionally cephalopods (Pereira et al., 2011). They are believed to feed on the most abundant mid-water species between 0 and 750 m depth.

 

Distribution and abundance:

The species is found more often on the North East Atlantic than on the East coast of the United States. Sightings have been confirmed in the Norwegian Sea, south of Iceland, west of Norway, north and west of the British Isles and Ireland, around the Faroe Islands, in the Channel Approaches and in the Bay of Biscay (Evans et al., 2008; McLeod, 2000, 2005). It has also been observed closer to the Azores and Madeira.

Acoustic work conducted west of Ireland detected a wide distribution but with the highest occurrences in May off northwest Ireland (Kowarski et al., 2018). There is however no population estimate.

 

IUCN Red List of Threatened Species™ Assessment

  • LC (Least Concern) globally, last assessed in 2020
  • DD (Data Deficient) in European waters, last assessed in 2007

 

Threats:

Threats to the species are currently unknown, although they are likely similar to other beaked whales’, that is mostly related to underwater noise disturbances such as mid-frequency active sonar. Other threats could include entanglements in fishing gear such as driftnets and alterations of their habitats due to global climate change (Learmonth et al., 2006; Waring et al., 2001).

 

Assessment information
CMS InstrumentsASCOBANS, ACCOBAMS, Western African Aquatic Mammals
IUCN StatusLeast concern
Geographic range
Countries France (Status: Unknown), Ireland (Status: Unknown), Norway (Status: Unknown), Portugal (Status: Unknown), Spain (Status: Unknown), United Kingdom (Status: Unknown)

No pictures for Mesoplodon bidens

Common names
EnglishSowerby's Beaked Whale
Taxonomy
ClassMammalia
OrderCetacea
FamilyZiphiidae
Scientific name Mesoplodon bidens
Population size and trend
Population Size interval Size quality Estimated population size Size reference Size notes
Trend interval Trend quality Trend Trend reference Trend notes
Northern East AtlanticNone3,518 (CODA Surveys)* Project Report: Review of Trend Analyses in the AS [more] The population size estimate is based on data collected during SCANS-II (2005) and CODA (2007) surveys. See the previous Trend Analysis document for more details. SCAN-II and CODA reports can be found in the additional notes section. *Note: the estimated population size is for the whole survey area and not just for the Northern East Atlantic. The separate estimate for this region is not available. All sightings of Sowerby's Beaked Whale were during the CODA survey.
NoneUnknown Project Report: Review of Trend Analyses in the AS [more]
Central East AtlanticNone3,518 (CODA Surveys)* Project Report: Review of Trend Analyses in the AS [more] The population size estimate is based on data collected during SCANS-II (2005) and CODA (2007) surveys. See the previous Trend Analysis document for more details. SCAN-II and CODA reports can be found in the additional notes section. *Note: the estimated population size is for the whole survey area and not just for the Northern East Atlantic. The separate estimate for this region is not available. All sightings of Sowerby's Beaked Whale were during the CODA survey.
NoneUnkown Project Report: Review of Trend Analyses in the AS [more]
Bay of BiscayNone3,518 (CODA Surveys)* Project Report: Review of Trend Analyses in the AS [more] The population size estimate is based on data collected during SCANS-II (2005) and CODA (2007) surveys. See the previous Trend Analysis document for more details. SCAN-II and CODA reports can be found in the additional notes section. *Note: the estimated population size is for the whole survey area and not just for the Northern East Atlantic. The separate estimate for this region is not available. All sightings of Sowerby's Beaked Whale were during the CODA survey.
NoneUnknown Project Report: Review of Trend Analyses in the AS [more]
Other details
Additional notesA SCANS-II report can be found here: http://biology.st-andrews.ac.uk/scans2/inner-furtherInfo.html and here http://biology.st-andrews.ac.uk/scans2/documents/final/SCANS-II_final_report.pdf. A CODA report can be found here: ttp://biology.st-andrews.ac.uk/coda/documents/CODA_Final_Report_11-2-09.pdf. The notes in the Threat section (Related Content) refer to the level of importance needed to address causes of mortality (identified from post-mortem examinations) of cetaceans in the ASCOBANS Agreement Area. This information also comes from this report: Project Report: Review of Trend Analyses in the ASCOBANS Area (AC18_6-05_ProjectReportTrendAnalysis_Corr.pdf). Updates have been made in August 2021 as per European Whales, Dolphins and Porpoises by Peter G. H. Evans (2020) unless stated otherwise.

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