Scientists used under water microphones to listen to the whales
Scientists on Shetland believe they may have discovered a previously-unobserved technique being used by killer whales to catch herring.
Researchers from Aberdeen and St Andrews Universities recorded the whales emitting a low-pitched noise which caused the fish to bunch up.
The mammals then stun the fish with their tails before eating them.
The scientists said this behaviour has not been seen anywhere else in the world.
The findings have come to light in the BBC2 series "Simon King's Shetland Diaries".
Whale researcher, Dr Volker Deecke, demonstrated how his team used underwater microphones to record unusual sounds made by killer whales.
They included a low-pitched noise that the researchers believe caused the herring to bunch up in a tight shoal.
The whales then slap the shoal with their tails to stun the fish before killing and feeding on them.
It is only a theory at this stage and studies will resume in the summer, but the evidence is described as compelling, even though this behaviour hasn't been seen before in any orcas anywhere else in the world.
The use of a herding call was first described from Iceland by research colleagues of Dr Deecke.
However, it was believed that this hunting technique was confined to Iceland, as other killer whale populations feeding on herring did not appear to use it.
Scientists said the fact that the herding call had been recorded in the waters around Shetland suggested that the large groups of killer whales seen feeding offshore are part of the Icelandic herring-feeding population.
Volker Deecke said: "It illustrates the value of doing acoustic research when trying to determine the population identity of killer whale populations.
Simon King on Shetland
"Even a short recording of sounds can answer questions that could take years of work using other methods such as photographic identification of individuals".
Simon King said: "There is something about the beast from the deep rising up. It is just amazing.
"These are sentient animals, with complex family structures, but being so close you really get the sense that there is so much more to these creatures than we currently know".
The research was funded by the Carnegie Trust for the Universities of Scotland with additional support from Scottish Natural Heritage and SEERAD.
You can see "Simon King's Shetland Diaries" at 2000 GMT on Thursday on BBC2.