The identity of a group of nine killer whales spotted off Scotland’s west coast remains a mystery, despite extensive investigations and a flurry of sightings of the species in recent weeks.
The unidentified pod, which includes two adult males and two youngsters, was first seen near the remote island of Vatersay, in the Outer Hebrides, during a marine wildlife survey carried out last year.
Now researchers from the charity Hebridean Whale and Dolphin Trust (HWDT) are hoping to catch further glimpses of the strangers in a bid to gain greater insight into the creatures frequenting Scottish waters.
Dr Lauren Hartny-Mills, science and policy manager for HWDT, said: “Securing good photographs of these killer whales has allowed us to carry out some detective work using photo-identification techniques. This involves matching identifying features on individual animals to database records to see if they have been seen before.
“But despite our collaboration with other organisations and experts to identify the animals, the pod remains an enigma. It shows there is still a lot to discover about the cetaceans visiting Scottish waters.
“We’re hoping to encounter these killer whales again during our 2019 expeditions and with help from our colleagues across Scotland and beyond, we really hope to find a match and learn more about this group.”
Because the group does not match up with any known orcas, the team believes the animals could belong to a wider offshore population that is roaming Scottish seas.
Killer whales – also known as orcas – are not actually whales, but members of the dolphin family. They are one of the world’s most widespread cetacean species, ranging from warm tropical waters to the polar regions.
There are two well-known groups found in Scotland.
The most commonly spotted is known as the West Coast Community, which consists of up to eight individuals.
The wide-ranging pod can be seen up and down the entire west coast of the UK, though most sightings are around the Hebrides.
But the group, which has been monitored for around 25 years, is at imminent risk of extinction as no calves have ever been seen.
In recent years there have only been confirmed sightings of two bulls from the pod – John Coe, who is easily identifiable due to a distinctive notch in his dorsal fin, and Aquarius.
Earlier this month they were spotted near Gairloch, in the north-west Highlands, and then again off County Clare in Ireland.
The other well-documented Scottish pod is the Northern Isles Community, which is mainly seen around Orkney, Shetland and the north coast of Scotland.
Five of its members, including the well-known male Busta and a female named Razor, were sighted off Handa Island, off the west coast of Sutherland, during a recent HWDT research expedition.
Marine mammals face a range of threats, including climate change, entanglement, pollution, underwater noise and habitat degradation.
The researchers say ongoing and long-term research is crucial to improving understanding of the impacts of human activities on cetaceans and basking sharks and how to protect them in the future.