August 20th, 1995

We've sailed out into Stephens Passage to see how things lie. Fred Sharpe, a young biologist who has spent the past three years studying the whales in this area has gone on ahead in his tiny boat and reports by radio that he's on whales and they're feeding. We are seeing wildlife all around us. We've already seen a bear and bald eagles seem as common as seagulls. We are also seeing evidence of the krill, small herring, and fry of several fish species on which the whales feed. They occur here in schools measuring tens of thousands of tons, and provide the gargantuan feasts that lures the whales to the area. Elsewhere in the world, humpback whales normally feed on smaller food they can catch easily. But the fast-swimming fish that are their diet here have forced them to invent new strategies to catch them.

The one that Fred is watching and that we're hoping to film is called communal bubble netting, one version of bubble netting. Humpbacks make nets out of bubbles by swimming in a circle beneath a small school of fish while releasing air from their blowholes. The bubbles rise around the school like a net and the fish avoid it by clustering together in the center-just what the whale wants. The whale then comes up from below with its mouth open and engulfs the whole school, the fish in it leaping through frantically through the surface trying to escape the jaws. Sometimes two whales do this together, but sometimes several form a stable hunting group and cooperate to catch fish. In this case one whale spins a single enormous bubble net around the fish and the other whales and then everyone breaks through the surface together with mouths wide-open.

During the process of making the net one of the whales is screaming -- almost certainly the one that is making the bubbles. Fred Sharpe has spent most of his three years here studying this kind of bubble netting intensively. In a series of elegant experiments in an aquarium, he demonstrated that the screams (which can be heard by the fish) cause the fish to cluster together, and that if the whales flash their white flippers at the fish it scares them into a tight cluster. Of course, both the screaming and the flipper flashing produce just the effect the whale wants -- concentration of the fish it wants to catch. Bubbles are a tool used by humpback whales to concentrate their prey. Yes, humpback whales are a tool-using species.