By Popular Demand: Bubble Net Feeding

WC’s recent post on Brandt’s Cormorant mentioned and photographed Humpback Whales engaged in a form of cooperative feeding called bubble net feeding. Humpbacks and Bryde’s Whales – a species WC has never seen – are the only whales known to engage in this fishing technique.

In Humpbacks, one to fifteen whales swim around a school of bait fish in a tightening spiral, emitting a continuous stream of bubbles from their blow holes. The bubbles act like a kind of tightening net, forcing the baitfish into a tighter and higher ball. Then other cooperating Humpbacks swim up, mouths wide open, through the ball of fish, lunging through the surface. Despite their mammoth size – up to 50 feet long and weighing 30 tons – a Humpback’s throat is less than five inches in diameter. It’s simply impossible for a Humpback to swallow larger prey, and they don’t have teeth so they can’t chew.

Every Humpback WC has seen feeding, WC has viewed from near-sea level. So WC has borrowed a NOAA photo to give you a view from above.

Classic spiral bubble net, with lunge. Photo by Christin Khan, NOAA / NEFSC

From sea level, the bubble nets are not so obvious, but you can still make them out. And the cloud of birds hovering over it is a pretty good clue.

Bubble net, with fish eating birds in attendance, Monterey Bay, California

WC was out on Monterey Bay in Fall 2018 to photograph pelagic birds, not whales, on a Debi Shearwater tour.¹ Many, but by no means all, pelagic species attend to bubble net-feeding Humpback Whales. In this flock, you can find Brown Pelicans, Western, Glaucous-winged and Heerman Gulls, Sooty Shearwaters, Common Murres and Brandt’s Cormorants, among many others. In the water are Risso’s Dolphins, California Sea Lions, Harbor Seals and Northern Fur Seals.

And then, without any warning, a group of Humpbacks explode out of the water.

Four Humpbacks lunging through a ball of baitfish (photobombed by a Sooty Shearwater), Monterey Bay, California

Humpbacks have pleated necks, that expand enormously to hold water and fish. As the whales rise out of the water baleen plates serve as strainers, with the water pouring out and the fish being mostly held in, then swallowed. As much as 2.5 tons of fish per day per whale.

To understand why there are so many other fish eaters in attendance, we’ll zoom in on the water spilling out of the mouths of these Humpbacks.

Pretty obviously, the Humpbacks are less than precise in capturing the fish. There’s lots of stunned baitfish flopping around near the surface.

Feeding flock on the footprint after the Humpbacks dove

That was fun. Let’s do it again.

Another bubble net; note the Risso’s Dolphin in lower left

And, once again, the Humpbacks lunge upwards through the baitfish.

Three lunging Humpbacks and on the far right the whale that generated the bubble net

These few photos can’t begin to convey the experience. Imagine hundreds of birds calling, the splash from the whales lunging and diving, seals and sea lions barking and the sound and mist of exhale as the Humpbacks spout. If you ever have the chance to see Humpback Whales foraging, you should take it. It’s a lifetime thrill.

Blue Whale, Monterey Bay, California

And if you are very lucky, you might just have a Blue Whale, the largest animal to ever live on this planet, cruise through to see what all the excitement’s about.

¹ Debi Shearwater retired after the 2019 season, after 41 years of guiding pelagic tours out of Monterey. It was a huge loss for the birding community. There are other pelagic and whale-watching tour operators out of Monterey Harbor, and they are probably very good, but they aren’t Debi Shearwater.