Hans J Marter
25 August, 2008
resident killer whales live off common seals, have an intensive social life and
are the pride of islanders.
These are the preliminary findings of a three month field study carried out by a
group of marine scientists from the universities of Aberdeen and St Andrews.
Their visit to the isles was part of a long term study into the population
structure and identification of killer whales around Scotland's coast.
They have had numerous close sightings of groups of the cetaceans in Shetland
waters, but mainly of a group of five animals and an individual male.
Speaking before leaving Shetland, Dr Andy Foote, of Aberdeen University, said
the project had so far identified around 25 of the estimated 30 to 40 orcas that
live in Shetland's coastal waters.
Dr Volker Deecke, of St Andrews University, added: "We have learned, first of
all, that some of the animals are quite resident. We have followed a group of
five animals for a six week period.
"A big part of their diet during that time was marine mammals. We didn't know
when we came here whether they were fish or mammal eaters, or whether they eat
both. We were able to document that they were always feeding on marine mammals.
"That ties in with the acoustic as well. The animals are extremely quiet, they
don't call very often, and that is consistent with them hunting marine mammals,
because marine mammals have good underwater hearing. All the predation we
witnessed were harbour seals," he said.
Researcher Harriet Bolt said the killer whales’ eating habits had contributed to
the decline of the local seal population.
The team found that the group structure of animals was rather "fluid", giving
rise to speculation that animals were gathering purely to hunt together.
Deecke, who had previously carried out orca research in the Pacific, said the
local behaviour was different to what he had experienced elsewhere.
"We found that the killer whales we followed this summer were very different
from killer whales in the Pacific that live in very stable groups, or at least
some populations do. Some animals never leave the group, they are born into the
group and they die in the group.
"Here it may be an adaptation for different hunting strategies, in that they
form bigger groups when hunting certain prey. But that is speculation," he said.
The team said that local people had been “brilliant” in supporting their
research by alerting them to killer whale sightings and providing a wealth of
"You really get the sense that these animals are part of people's lives. Local
people are proud of them, thrilled to see them, and keen to show them to other
"Islanders have been very supportive of our research work. It was a real
pleasure working up here,” Dr Deecke said.
The team is now back on the Scottish mainland where they will spend the next few
months working their way through photos, genetic material and acoustic recording
before returning to Shetland next summer.
Dr Foote, however, will be back in the isles in October when he joins skipper
George Anderson on board the pelagic trawler Adenia heading for the
During the last few years, Dr Foote said, he had observed groups of up to 50
killer whales feeding of mackerel off Shetland.