What Is Bubble-Net Feeding? How Humpbacks Hunt Together

How does bubble-net feeding work?

Humpback whales are baleen whales, so they cannot chase and bite single fish. Instead they need prey packed densely enough to be worth a gulp. Bubble nets solve that problem. A typical sequence looks like this:

1. The whale, or group of whales, finds a school of fish or a swarm of krill and dives below it.
2. Swimming in a circle or upward spiral, a whale releases air, usually from its blowhole, leaving a ring of rising bubbles.
3. The fish or krill avoid crossing the wall of bubbles and are herded into a smaller and smaller space.
4. The whales swim up through the center with their jaws open, letting their pleated throats balloon out as they take in water and prey.
5. At the surface they close their mouths and push the water out through their baleen plates, which trap the food.

From a boat, the first sign is often a ring of bubbles fizzing at the surface, followed seconds later by open mouths breaking through in the middle, often with gulls diving on the escaping fish. Tag studies on Stellwagen Bank, off Massachusetts, identified two main net shapes: an upward spiral and a “double loop”, in which a large, deep loop of bubbles herds the prey before the whale slaps the surface and blows a smaller second loop. For the filtering step, see What are baleen whales?

Group bubble-netting in Alaska

The most famous bubble-net feeding happens in summer in Southeast Alaska, where groups of humpbacks hunt schools of herring together. Groups can range from a few whales to about 15 or 20, and in some areas the same whales come together year after year.

Researchers who have followed these groups describe different roles. One whale blows the bubble net, while others appear to herd the fish. One whale often makes a loud, trumpet-like “feeding call” for several seconds before the group lunges. The call may help coordinate the whales and may also frighten the herring into a tighter school. Then the whole group rises together, sometimes a dozen or more mouths breaking the surface side by side.

Southeast Alaska is the best place in the world to watch it, especially around Juneau, Chatham Strait and Frederick Sound from about June to September. More about the region’s wildlife is in animals of Alaska.

Bubble-net feeding in the Gulf of Maine and elsewhere

Humpbacks in the Gulf of Maine, off New England, often hunt alone or in pairs and blow nets, clouds and columns of bubbles around schools of sand lance. Since 1980, many of them have added an extra step: they slap the water hard with their tail before blowing bubbles, a technique called lobtail feeding. A 2013 study tracked how it spread over 27 years and found that whales learned it from the whales they spent time with. By 2007, more than a third of the population had been seen using it.

Bubble-net feeding is also seen in other parts of the North Atlantic and North Pacific and in the Southern Ocean, where humpbacks blow bubble nets around krill along the Antarctic Peninsula. The details vary from region to region, which is one reason scientists think the behavior is partly cultural.

Is bubble-net feeding tool use?

A 2024 study argued that it is. Researchers used suction-cup tags and drones to follow solitary humpbacks feeding on krill in Southeast Alaska and analyzed 83 bubble nets. The whales built nets made of several internal rings and appeared to control the number of rings, the size and depth of the net and the spacing between bubbles.

By shaping the nets this way, the whales took in on average about seven times more krill per lunge, without spending more energy. Because the whales make and control a structure outside their own bodies to catch food, the authors suggest that humpbacks are among the few animals that both make and use tools, alongside chimpanzees, some birds and a few others.

Other ways humpback whales feed

Bubble nets are only one of several techniques. Humpbacks are flexible hunters and switch methods depending on the prey and the place.

• Simple lunge feeding: charging into a dense school or swarm and gulping it, as other rorquals do. The giant version is described in What do blue whales eat?
• Surface lunges: rising sideways or vertically through prey near the surface, often with mouth agape.
• Flick feeding: flicking the tail forward over the head to drive prey toward the mouth.
• Bottom feeding: on Stellwagen Bank, humpbacks roll onto their sides and brush their jaws along the seafloor to flush out sand lance.
• Trap feeding: in British Columbia, some whales rest at the surface with their mouths open, and fish seeking shelter swim right in. The behavior was first described in the 2010s and has since spread.

Why bubble nets work so well

A humpback whale needs to eat large amounts of food in a few months, because it eats little during migration and on the breeding grounds. Each lunge costs a lot of energy, so a whale gains the most by filling its mouth with the densest possible prey. Bubble nets do that by concentrating fish and krill that would otherwise be spread out.

Bubble nets are especially useful when prey patches are thin, when a single lunge into scattered fish would not be worth the effort. They also let whales feed close to the surface, where they can breathe between lunges without long dives.