Unusual whale and dolphin wash up on the Scilly Isles

01/09/2008 17:00:12 September 2008. Two highly unusual marine mammals have been washed up on the western shores of the Isle of St Agnes within days of one another.

Sadly, both animals were already dead but this provided a unique opportunity for local scientists to examine them. A very rare female Sowerby's beaked whale was washed up at Periglis. These are normally deep water species, feeding on squid and cuttlefish. At nearly 12 feet long, this animal was too big to be taken for postmortem.

However, members of Cornwall Wildlife Trust's Marine Strandings Network were able to collect measurements, photographs and skin samples that will be analysed by the Institute of Zoology. This whale species is very hard to spot at sea which makes any study of live animals difficult and it is extremey rare to see one here in the south west.

St Agnes Coastguard Mike Hicks, who found the animal, said, "It was sad to see such an impressive animal out of her natural environment but I'm pleased we were able to help gather information from her and at the end of the day it was a privilege to see something that most people never will".

Baby Risso's dolphin
Just as the Trust's Marine Strandings Network volunteers had returned to the mainland, Mike was alerted to another, smaller animal a quarter of a mile away from the Sowerby's whale. Mike sent photographs to the Marine Strandings Network volunteer co-ordinators to confirm the identification of the animal. The animal was identified as a baby Risso's dolphin that was young enough to still be dependent on its mother for nourishment. Mike's report sparked a huge effort involving many people and organisations to bring the animal back for postmortem at the Veterinary Laboratories Agency in Truro.

Risso's dolphins are often seen around Cornwall, although not as frequently as bottlenose and common dolphins. What was particularly interesting about this baby was that initial observations suggested it had been killed by bottlenose dolphins. This phenomenon has been recorded in Scotland's Moray Firth, however that was bottlenose dolphins attacking and killing harbour porpoises. The motives for such attacks are unclear, although scientists have considered that competition for declining food stocks may trigger the behaviour.

Infanticide (killing of offspring) is also known amongst bottlenose dolphins in Virginia in America and has been considered an influence with this species practising their agressive skills on their smaller cousins in UK waters.

Bottlebose dolphin aggression
Jan Loveridge, volunteer co-ordinator for the Trust's Marine Strandings Network, said, "Despite their friendly image, bottlenose dolphins can be aggressive towards one another and on the rare occasion that we see a dead bottlenose wash ashore, it often has rake, or tooth marks inflicted by its own species. However, we have recently begun to see an increase in the numbers of young and female harbour porpoise that have clearly been attacked by bottlenose dolphins and results from the post mortems carried out on these animals confirm this".

The discovery of another species that has probably suffered from these attacks is of particular interest, especially as it was so young. It was very important, despite the difficulty involved, that the Risso's dolphin should undergo a postmortem examination'.

If you would like to become involved with the work of the Isles of Scilly and Cornwall Wildlife Trust's Marine Strandings Network please visit www.cwtstrandings.org . For more information on the wider work of Cornwall Wildlife Trust visit www.cornwallwildlifetrust.org.uk .

To report any dead stranded marine animal please call our strandings Hotline on 0845 201 2626 straight away.