Posted by Brydon Thomason on Thursday 14th April 2011 | Sea Mammals in Shetland

Although behaviourally there is similarity between Sperm and Humpback raising their tail flukes, in appearance they are quite different especially as Sperm lack the prominent white undersides. Their massive bulbous head can measure up to 30% of their overall body length.

On the 7^th of April I received a text from David John Anderson, a friend of mine working on board the Skerries ferry, MV Filla. His text described very briefly a large whale which he believed to be a Humpback which they had seen and photographed from the ferry mid-way between the Mull of Eswick and the North mouth of Lerwick Harbour. Needless to say on reading the message I was quick to call him back. His description firstly of the whale lying motionless at the surface quickly urged me to mention Sperm Whale’s characteristic ‘logging’ on the surface. Their views however were leading them much more along the trail of a Humpback and they seemed fairly convinced that that was what it was.

Incredibly Sperm whales have been known to dive to depths of 1000m or more and stay down for over an hour! They have the largest brain of any animal.

Later that evening however DJA downloaded his images and with a brief search of the internet compared them to Sperm and Humpback and tentatively re-identified the whale from his own images. Opening up the images he sent I was green with envy as he was indeed spot on and I have yet to see Sperm Whale in Shetland! As far as records of the species go here they are very much a rare sight inshore. The most recent report inshore off Shetland was back in 2007 when a pod of up to 20 whales were believed to be Sperm whales and before that there were at least 12 off of Noss in 2005. ‘None stranding’ reports or sightings such as these usually refer to pods on their migration. Further offshore they can be seen much more regularly. This sighting most probably involved a male on his Northward migration. The whale was estimated by the ferry crew to be in the region of 40-50 foot in length!

A big thanks and well done to DJA for the haste in getting the news to me and for the use of his images.