Unusual Whale and Dolphin Wash up on the Scilly Isles
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.
Wildlife Extra: September 2008
