Whale bubble nets

If you want to fall into a black hole of the internet, may I recommend whale "Bubble nets."

Single sentence summary: To aid in hunting, some whale species implement the use of bubble nets by diving below a school of fish or krill and blowing bubbles to encircle and trap the fish before diving upwards to consume them.

Image generated by DALL-E, OpenAI, using a prompt provided by the user via ChatGPT. September 2024.

Longer form thoughts

I happened upon these structures during my search for aquatic architects. One committee member pointed out they are more a tool than an architecture. (And in fairness, the scientific literature on the topic definitely backs him up. )To which I countered, "I'm not sure the fish in the middle of it would agree with you."

But to his point, this is a structure that is all about scale: what serves as a tool for the whale is an unpassable architecture to the fish, and it all comes down to size. I certainly enjoy the idea that a bubble net can both be a "tool" and a piece of "architecture". I'm happy to let you argue this one out in the comments, though.

To be honest, sounds like a terrible and terrifying way to die. Can you imagine? Swimming, minding your own business, and suddenly bubbles are rushing past you, pushing you against your will, to a spot that your instincts shout as dangerous. It probably loud , turbulent, and confusing. By the time you've figured out what is happening (if you figured it out all), you're being swallowed by a giant mouth, almost too wide for you to even recognize it as a mouth.

Bubble nets are an excellent case study for physics. Apparently, bubble nets are "loud" . Sound, at its essence (like most things I find interesting in physics), is a pressure differential moving through a medium as a wave. An air pocket in the water creates a pressure differential, ensuring a rush of water and a confusing roar of sound that you would wisely try to swim away from to the quiet center of the net... Suppose you manage to move outside of the quiet point. In that case, you'll be hit another wall of sound and bubbles, effectively herding you and the school of fish you are traveling with together.

The acoustics of the ocean is a rich research topic that is becoming more known as classified data of the soundscape of our oceans recorded during the Cold War is becoming declassified. Additionally, our recording technology is improving. Fish and whales sing, lobsters and crabs percuss, and us humans make far too much noise.

Bubble nets can only be generated at shallow enough depths (approximately 18 m.) (which is still terrifyingly deep). At a certain depth, the pressure is too high to blow air. Whales have found a workaround for this. In Alaska, a group of unrelated male humpback whales meet annually and work together to hunt . One whale will dive deep, herding herring upwards to a depth shallow enough to build a bubble net. At these depths, two whales are waiting. Once fish are within range, they begin to build. Surrounding their prey with bubbles. Only the whales herding the prey are able to eat. The whales work together and coordinate, take turns, and engineer.

Bubble nets (and whales in general) also break the human collective brain when it comes to thinking about intelligence, culture, communication, and coordination. Whales appear to have different styles of making bubble nets worldwide - implying a cultural preference or at least a learned one. Young whales have been recorded as trying and failing to produce an adequate net.

Double barrels are favored in the Atlantic Ocean off of North America, coordinated spirals are favored by the large males in the Northern Pacific, spirals have been observed by solitary whales off the coasts of Scotland, some whales will reinforce their nets with their fins, herding more fish to their doom.

While humpback whales (Megaptera novaeangliae) get most of the credit for the bubble net hunting technique, this bubble-blowing technique to confuse and capture prey has been observed in other cetaceans as well, including the killer whale (Orcinus orca) and the Bryder's whale (Balanoptera edeni). Dolphins (Tursiops truncatus) are also net builders, preferring the use of mud (perhaps a blog post for another time).​

Bubble nets are also an interesting way to think about geometry, spatially and temporally. In Scottland, a solitary whale was observed to make a beautiful Fibonacci spiral-shaped net. It is practical to start wide and circle closer to the fish in narrowing loops until they are grouped perfectly to fit inside of your mouth. It may imply a certain appreciation of geometry and art on the whale's part. Whether or not the visuals of the bubble net inspire whales or not, it certainly inspires us, humans. 

References:
[1] Szabo, A., et al. "Solitary humpback whales manufacture bubble-nets as tools to increase prey intake." Royal Society Open Science 11.8 (2024): 240328.

Qing, Xin, et al. "Three-dimensional finite element simulation of acoustic propagation in spiral bubble net of humpback whale." The Journal of the Acoustical Society of America 146.3 (2019): 1982-1995.

Kosma, Madison M., et al. "Pectoral herding: an innovative tactic for humpback whale foraging." Royal Society open science 6.10 (2019): 191104.

Marwood, Eleanor M., et al. "Account of a Solitary Humpback Whale (Megaptera novaeangliae) Bubble-Net Feeding in the Moray Firth, Northeast Scotland." Aquatic Mammals 48.6 (2022).

Moreno, Kelsey R., and Riley P. Macgregor. "Bubble trails, bursts, rings, and more: A review of multiple bubble types produced by cetaceans." Animal Behavior and Cognition 6.2 (2019): 105-126.

Ramos, Eric A., et al. "Lords of the Rings: Mud ring feeding by bottlenose dolphins in a Caribbean estuary revealed from sea, air, and space." Marine Mammal Science 38.1 (2022).

Kato, Hidehiro, and William F. Perrin. "Bryde’s whale: Balaenoptera edeni." Encyclopedia of marine mammals. Academic Press, 2018. 143-145.

Baird, Robin W. "The killer whale." Cetacean societies: field studies of dolphins and whales 127 (2000): 153.