True's beaked whale

Mesoplodon mirus
Other names: 
  • n/a
Maximum length: 
  • Male: 5.3m
  • Female: 5.4m
  • Calf: 2m
Maximum weight: 
  • Male: Unknown
  • Female: 1,400kg
  • Calf: Unknown
Diet: 
  • Squid (and probably some fish)
Estimated population: 
Unknown
IUCN Listing: 
DD
CITES Appendix: 
II
CMS Appendix: 
Not Listed
Classification: 

True's beaked whale is found in two geographically distinct areas, and these populations may soon be separated into two subspecies or even separate species. Positive identification at sea is extremely difficult and in the northern reaches of the range it can be virtually impossible without a clear view of the head (of males only), to distinguish between a True's and a Gervais' beaked whale.

Appearance: 

Like other beaked whales identification can be confirmed by the two small teeth at the tip of the lower jaw which are visible in the male even when the mouth is closed. Like other beaked whales True's beaked whale has a flipper pocket. This is a small depression on each side of its body immediately behind the point where the flipper is joined to the chest area. The flipper pockets have only been seen during examinations of stranded animals and are thought to assist in streamlining the whale on deep dives. True's beaked whales have a blue-grey body with white scratches and scars on the back and sides. In the southern hemisphere, individuals have a lighter back and tailstock, making them easier to identify.

Behaviour: 

True's beaked whale has only been positively identified at sea a handful of times and so very little is known about its behaviour. Observations have recorded repeated breaching behaviour and the tendency to break the surface of the water at an angle, beak first. Scratches and scars on the few stranded animals suggest competition between males.

Distribution: 

True's beaked whales appear to have a preference for colder temperate waters. The majority of stranded specimens have been from the western North Atlantic off the east coast of the USA although some have occurred on the west coast of Ireland south to the Canary Islands. In the southern hemisphere they have been recorded from South Africa, Australia and Brazil. True's beaked whales are not known to have been commercially exploited however bycatch is thought to be a threat with reports of True's beaked whales being caught in gillnets off the east coast of the USA. Noise pollution and climate change are also thought to impact this species. There is no population size estimate and the species is listed as Data Deficient by the IUCN.

Distribution map: