Clip of the Week
This week’s Clip of the Week shows two killer whales hunting within a shoal of Atlantic herring, Norway. The clip was filmed by Espen Bergersen. The whales force the herring into a tight ball by releasing bursts of bubbles or flashing their white undersides, then slap the ball with their tail flukes, stunning or killing many fish, before eating them.
This cooperative hunting behaviour is known as carousel feeding, and is only observed in Norwegian killer whales. The strategies orcas develop depend on their typical prey type and the most efficient method to capture them, considering environmental conditions. Norwegian orcas have developed carousel feeding because it is an effective method to prey on the abundant spring-spawning herring shoals. The herring population is not completely depleted because the orcas never eat the whole herring ball, so husbanding a resource for the future. In theory, the strongest and fittest herring will escape the orcas, and go on to breed and increase the fitness of the herring population as a whole.
Espen shares the rarity of the footage he obtained
“This clip was captured on a freezing cold day in January. The original plan was to look for whales from my boat, but with – 12 °C outside I couldn’t start the boat engine. I then decided to look for whales travelling along the coastline by car. When I arrived at a place called Sommarøy in Northern Norway, I observed a group of orcas and humpback whales feeding on herring close to shore. I was able to park my car very close to where the whales were feeding, and decided to try out my drone, a Dji Phantom 3 pro. Standing at the shoreline, I didn’t realise how spectacular this would look from the air. The footage of killer whales swimming inside the herring school in shallow water is something unique. From a drone in the air, I could clearly see the enormous school of herring as a huge dark rounded patch/shape against the green sea-floor. Even better, the herring were being hunted by both orcas and humpback whales! It was amazing to see how the herring tried to escape the orcas when they were swimming through the school. One could also clearly see the Orcas hunting technique where they used tail-slapping to stun the herring before eating it one by one. This was really an unique situation since the herring normally stay in deeper waters where they are difficult to see. In 9 seasons I have only seen this situation once.”
You can see a showreel video (featuring both video clips and still images) of Espen’s killer whales / humpback whales feeding on herring here.