Scott Portelli: Australian Geographic Nature Photographer of the Year winner

When Scott Portelli witnessed this amazing display of ‘bubble-netting’ by a group of humpbacks in the Antarctic, he didn’t just see it – he heard it.

As the whales tightened their circle, the ‘net’ drew in, until the krill were in a tight ball. Picture: Scott Portelli

They’d spent five days crossing the wild Southern Ocean in a 60ft yacht named Spirit of ­Sydney. Now, in Antarctic waters, ­photographer Scott Portelli and his eight crewmates stood on the vessel’s deck, rapt by the behaviour of a group of humpback whales around them. Snow was falling on this February day, and icebergs drifted nearby. In the distance, icy white mountains formed a jagged horizon. The four whales were practising a group hunting technique known as “bubble-netting”. It’s a learned behaviour, rather than instinctive, scientists say – and it requires collaboration, co-ordination and communication between these mysterious animals. The communication is what Portelli and his mates were so amazed by. They weren’t just watching the spectacle play out, you see. They were hearing it.

All of the Southern Hemisphere’s humpback whales congregate in Antarctica in summer, and spend several months there feasting in the rich waters, fattening up, before making the 7000km schlep north to their breeding and calving grounds in the tropics. This drone image, overall winner of the Australian Geographic Nature Photographer of the Year awards, gives a bird’s eye view of the action beside Spirit of ­Sydney. The group of whales had located a swarm of krill – small, shrimp-like crustaceans – then dived under it and began circling around, exhaling air. Krill won’t try to swim through a wall of rising bubbles; they were effectively corralled. As the whales tightened their circle, the “net” drew in, until the krill were in a tight ball – at which point the whales took turns to shoot up through the centre with their ­colossal maws open, gulping them down.

All this was happening underwater, of course, so you might be wondering how on Earth those aboard Spirit of Sydney could hear the whales communicating as they went about their attack. The answer is the boat itself: its steel hull acted as a giant resonating chamber, like a 60ft-long musical instrument, picking up the sound in the water and broadcasting it into the freezing air of that February day. “Long, low-pitched wailing sounds,” is how Portelli describes it. Then the 52-year-old, who’s now back at home in Esperance, WA, attempts to mimic the sound down the phone line. You know what? It sounds exactly like humpback whales, only with an Aussie accent.