Beaked whale update …. identification of the True’s beaked whale from Winterstrand

The whale stranded last year (19th October 2016) has been positively identified as a True’s beaked whale (Mesoplodon mirus) after the skull was macerated.  This was also confirmed after the teeth were surgically removed for identification by museum scientist Kevin Cole.

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True’s beaked whale on the beach east of the seaside village of Winterstrand. Photo: Kevin Cole ELM

The whale was reported by members of the public to Siani Tinley of the East London Aquarium and a first investigation revealed a bloated specimen with innards expressed at the mouth. The first record for South Africa of the species was a stranding in 1959.

The unique marking of the whale was not visible as the skin had started to darken after the animal had died and been exposed to the sun for a period of time. The usual markings for the species is illustrated below.

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True’s beaked whale – Reference: Whales and dolphins of the southern African subregion by Peter Best (Cambridge University Press 2007)

There have been no authenticated sightings at sea in the southern African subregion of these whales. Four stomachs examined for South African specimens stranded revealed a diet of unidentified fish species and 2 squid species.

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Mouth part of the whale illustrating the  lack of any visible teeth. Photo: Kevin Cole ELM

A single pair of mandibular teeth are only visible in the adult male of this species. The teeth do not erupt in adult female and juvenile True’s beaked whales. The stranded animal recorded here was a female (also confirmed by the genital anatomy and presence of mammalian glands).

The macerated skull revealed a long, broad based rostrum and the two teeth removed were consistent with the dimensions of an adult female (2.4-3.1 cm).

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Skull of the True’s beaked whale prepared by the East London Museum. Photo: Kevin Cole ELM

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Mandibular teeth (a single pair) removed from the female True’s beaked whale at Winterstrand. Photo: Kevin Cole ELM

There is no accurate population estimate on the species in the world’s oceans (they occur in the northern hemisphere as well). One of the  threats to the species is the negative effect of loud sounds generated when seismic exploration takes place (in search of gas and oil). This may have caused the demise of this species as seismic activity was recorded in our oceans a few months before this animal stranded.

Dr Greg Hofmeyr, Marine Mammal Curator at Bayworld Museum (Port Elizabeth, South Africa) is thanked for sharing his knowledge on marine mammals and for his encouragement to document cetacean strandings.

Wojtek Bachara, a Ziphiidae consultant from Poland, is also thanked for his input on beaked whales.

 

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About East London Museum Science

Conservation Biologist East London Museum South Africa
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