Whales, whales, whales and more whales. It’s been crazy here at Palmer Station, with a continuous flow of humpback whales through our little study area. Every day we see and sample a bunch of new whales – how’s that for scientific precision? Zach and I are tired but happy to be spending long days on the water with the whales.
The whales are down here in the Antarctic to eat, of course. They are returning to their feeding grounds after spending their winters fasting in the tropical waters of Panama and they are hungry. Like most of the other predators down here, their main prey is Antarctic krill Euphausia superba, the little pink crustacean that drives the ecological engine here along the Antarctic Peninsula. As a result, humpback whale poo (like penguin poo) is distinctly pink. We’ve already collected a couple of fecal samples – and, yes, it smells very, very bad.
Like all baleen whales, humpbacks feed by engulfing vast quantities of water and krill and then straining the prey through their baleen plates. We see this whole process unfold when the whales feed near the surface, as they burst into the air with their throat grooves massively distended and water spills out through their baleen.
It takes a lot of energy to engulf all that water, so to make the process profitable the whales must engulf very dense aggregations of krill. They improve their feeding by concentrating the krill using bubble nets, which are curtains of air expelled from their blowholes underwater. One or two whales swim upwards in a spiral, exhaling bubbles that trap the krill inside a cylinder of air. Then the whales lunge upwards through the cylinder with their mouths open, engulfing the krill. Have a look at some cool underwater pictures of the bubble net taken by Chris Linder from our boat.
Of course it’s one thing to describe this process in words on a page. It’s another thing altogether to see it done by a couple of 50-ton whales within touching distance of your very small rubber boat. We had Erin Pickett, a graduate student at Oregon State and a very experienced field biologist, out with us this afternoon. She quite literally squealed when she saw her first bubble net unfold next to the boat. It’s just that kind of a thing.