Drone footage has recorded how a harbour seal attempted to use the shelter of a mussel farm off Shetland to escape from a pod of orca.
Local drone pilot Nick McCaffrey captured 38 minutes of the hunt, which involved eight orca at the Grunna Voe mussel farm, operated by Shetland Mussels. The seal hid in between two lines of mussel ropes and was able to evade the whales for a time, but when it broke out and headed into open water it was caught and killed.
Emily Hague, a PhD student at Heriot-Watt University, said the interaction shows how marine mammals are increasingly interacting with manmade structures at sea.
She analysed the footage as part of her research into the impact of human activities on these creatures, and concluded that while the farm may have temporarily helped the seal, it was also placing the orca at risk.
Hague said: “Interactions involving man-made structures are rarely, if ever, caught on camera. This makes this footage extra special and very insightful from a scientific point of view.
“It gives us a whole new perspective on how marine life, in this case two top predators, are living with manmade structures in our seas.”
“It’s fascinating that these novel structures in the marine environment are potentially being used by prey to hide from predators.
“Interactions like this can also shed light on potential risks to marine mammals.
“Last year a juvenile member of this killer group died entangled in rope and was found on Orkney. If this group is spending a lot of time around marine structures, then this may have associated risks, like entanglement.”
Hague has published her full findings in the journal Aquatic Mammals (Issue 48.4) out today.
Nick McCaffrey and other wildlife enthusiasts were alerted to the orcas’ arrival by the Shetland Orca Sightings Facebook page and a dedicated WhatsApp group, both managed by wildlife photographer and guide Hugh Harrop.