Among the typical bubble-blowers, a few groups come to mind: children at birthday parties, babies experimenting with their nostrils, a lone goldfish in a bowl. None are particularly celebrated for their intellect. A new study, however, reveals that humpback whales also blow bubbles—a tool-using behavior scientists think attests to a high level of intelligence.
For humans, tools act as an extension of the body, allowing us to cut fruit, make fire, and unwind tiny screws—tasks that enhance our survival but that cannot be accomplished with bare hands. Researchers, though, view tools as an extension of the mind: the rich history of human tool use reflects the cognitive abilities that set us apart from other animals. As more studies are conducted in animal behavior, however, research is increasingly supporting the idea that tool use, while only found in species displaying high intelligence, is present and taxonomically widespread throughout the natural world; instances of tool use have now been documented in mammals, birds, fish, and even insects.
A 2021 study, for example, describes how wild Goffin’s cockatoos from the Tanimbar Islands in Indonesia use a set of stick tools to access the edible seeds of the Wawai fruit, a process not unlike a surgical procedure. After using thicker stick fragments to wedge open the fruit’s tough outer layer, the birds switch to thinner sticks to pierce the inner parchment encasing the seeds. A medium-thickness stick then serves as a spoon, allowing them to scoop out and eat the seed matter. The cockatoos even shape the sticks with their beaks and tongues to obtain the desired tool widths.
Humpbacks, however, are different beasts—how is tool manipulation possible in an aquatic environment, sans hands, for a 17-meter-long whale? For researchers at the Alaska Whale Foundation and the Hawai'i Institute of Marine Biology, the answer lies in the bubbles.
A Clever Feeding StrategY
In a study published in Royal Society Open Science, researchers describe the use of highly organized bubble structures, known as bubble-nets, by solitary humpback whales during foraging. By swimming in circular paths and releasing air periodically through their blowholes, the whales construct large, curtain-like columns of bubbles that serve as nets to trap krill.
To study this behavior in greater detail, the research team observed 70 humpback whales in Southeast Alaska in July 2019, using drones and tagging a subset of individuals with high-resolution cameras, microphones, pressure sensors, rotation trackers, and compasses. These tags allowed scientists to quantify the whales' speed and movement patterns during bubble-net use, as well as the rate of bubble production. Using online modeling tools, the team was able to recreate three-dimensional bubble-net models based on their observations. To support their data, the researchers conducted systematic boat surveys from 2019 to 2021, allowing them to study the frequency of bubble-net use in the area.
Bubble-Nets as Functional Tools
The study’s findings suggest that bubble-nets fit key criteria for tool use. They are external structures, intentionally manipulated, and provide a clear prey-catching advantage to humpback whales. Across all of the researchers’ observations, the bubble-nets followed a consistent clockwise pattern, with multiple circular rings that grew progressively smaller towards the interior of the bubble-net spiral. From their 3D models, scientists observed that the final, innermost ring of the whales’ bubble-nets was only twice the width of a humpback’s maximum mouth gape—the ideal size to maximize prey capture in a single mouthful
Importantly, whales also exhibit fine control over their bubble-nets’ structures. By varying the rate of bubble production while maintaining a steady swimming speed, whales can adjust the “mesh size” of the net, or the spacing between bubbles in the innermost ring. Researchers think this strategic adjustment likely reduces prey escape, corralling krill into the densest part of the net. Hydroacoustic data from tagged whales supports this hypothesis, showing that the whales deploy bubble-nets at depths where krill are present. Unlike schools of fish, krill typically are spread in low-density patches, making them harder to catch in large numbers. By trapping krill within tightly nested rings, however, humpbacks dramatically increase their prey’s density—sometimes by more than sevenfold—to catch more krill with less effort.
Indeed, one of the most significant findings for scientists is that bubble-net feeding does not increase the whales' energy costs. Whales using this method lunge at their prey at only 60% of the speed of those feeding without bubble-nets, minimizing energy expenditure. Additionally, their breath rates, an indicator of metabolic effort, are similar to those of whales feeding without nets, supporting the idea that bubble-net feeding provides a significant energetic advantage: more prey intake per lunge without additional effort.
However, despite these benefits, solitary bubble-net use appears to be relatively rare. Systematic boat surveys from 2019 to 2021 found that only 2.8% of the observed whales engaged in bubble-net behavior, despite the benefits it brings. Researchers hypothesize that while bubble-netting can offer an advantage under specific conditions—such as when krill are scattered, and hence not dense enough for typical feeding—it may not be beneficial under normal circumstances. Unlike traditional lunge feeding, which allows whales to take multiple lunges at prey per dive, bubble-netting requires whales to produce a single, highly controlled lunge per foraging attempt. Over extended periods, researchers say, this may limit the number of feeding opportunities.
A Strategy for Changing Oceans?
For scientists, the study’s findings highlight humpback whales’ intelligence, as their ability to create bubble-nets as hunting tools allows them to exploit prey patches that might otherwise be too sparse to be worth the effort. In our rapidly changing oceans, where prey distribution is shifting due to climate change and human activity, this behavioral flexibility could give humpbacks a key advantage over other whales with more rigid feeding strategies.
References:
NOAA Fisheries (2016). Humpback Whale | NOAA Fisheries. [online] Noaa.gov, available: https://www.fisheries.noaa.gov/species/humpback-whale.
O’Hara, M., et al. (2021) ‘Wild Goffin’s cockatoos flexibly manufacture and use tool sets’, Current Biology, 31(20): 4512-20, available: https://doi.org/10.1016/j.cub.2021.08.009.
Szabo, A., et al. (2024) ‘Solitary humpback whales manufacture bubble-nets as tools to increase prey intake’, Royal Society Open Science, 11(240328), available: https://doi.org/10.1098/rsos.240328.