The conservation status of a group of killer whales (Orcinus orca) off the west coast of Scotland is believed to be critical, according to emerging research findings from the Hebridean Whale and Dolphin Trust (HWDT).
The "west coast community," as it is known, is believed to consist of only nine animals. Their conservation status is thought to be critical since no live calves have been sighted since research began almost two decades ago. The group is the only "resident" population found in British waters.
Earthwatch scientists Nienke van Geel and Dr. Jonathan Gordon, of the HWDT, with the help of Earthwatch volunteers, are collecting data on whales, dolphins, porpoises and other marine life in the Hebrides. Their aim is to determine the cetaceans' use of habitats and to identify particular areas of importance, or "hotspots" for conservation.
As part of the research, HWDT and PhD student Andy Foote1 have been studying the small population of killer whales using photo-identification. This allows each animal in the group to be recognized by the unique shape and markings on its dorsal fins. These studies have revealed that there are four males and five females in the group. All the animals associate with each other, although some individuals are more regularly sighted together than others.
Photo-identification techniques have also helped the scientists to understand the wide-ranging nature of these predators; for example, recently, sightings as far afield as Ireland have been reported, including a sighting of all nine individuals off the Cork coast. One of the males was also sighted off the Pembrokeshire coast in 2008 and 2007.
Andy Foote's research into orca populations of the North-east Atlantic has shown that there is no association between the Hebridean orca and the groups found around the rest of Scotland's coast, mainly off the coasts of Orkney and Shetland. Moreover, recent findings have revealed that the populations are also morphologically different. Genetic analysis indicates the two types belong to two different populations - all suggesting separate ancestry.
Dr. Foote explains: "Type 1 specimens (groups found in the northern regions of Scotland, Iceland and Norway) were from closely related lineages, but the type 2 whales (the west coast community) were more closely related to a group of Antarctic killer whales."
Unlike the other orca populations in the North Atlantic, which feed primarily on pelagic fish and seals, HWDT still has little evidence of what the west coast group are feeding on, although it is likely that they are feeding on other marine mammals such as harbor porpoises, seals and possibly minke whales. Differentiation in tooth wear from stranded orca has allowed Dr. Foote to highlight this difference in diet and ecological niche; the west coast community has virtually no tooth wear, while in the other groups adults have worn their teeth down quite substantially.
Nienke van Geel says: "I find it really alarming that no calves have been seen in this group for such a long time. Especially since evidence indicates separation from other killer whale groups in the North Atlantic, the absence of calves might have major impacts on the continuity of the genetic diversity, and the ecological relations between prey and predators on the west coast of Scotland. It is vital that we maintain this research as we know so little about the role these animals play in our ecosystem, and we need the support of the public to do this."
Each year HWDT welcomes Earthwatch volunteers onboard its research yacht Silurian to collect data from onboard. These surveys, together with reports from the public and other organizations, are shedding light on Scotland's cetaceans.
Find out more about the Earthwatch expedition Whales and Dolphins of the Hebrides. Read more about HWDT.
1 Andy Foote is a PhD student from Aberdeen University. He is part of the North Atlantic Killer ID project (NAKID).
Killer whales off the west coast of Scotland.
Earthwatch scientists and volunteers are collecting data on whales, dolphins, porpoises and other marine life in the Hebrides.