New publication: The key to bubble-net feeding: how humpback whale morphology functionally differs from other baleen whales

Written by Cameron Nemeth

We are pleased to share a new publication in the Journal of Experimental Biology, entitled: The key to bubble-net feeding: How humpback whale morphology functionally differs from other baleen whales. Accompanying this publication is an Early Career Researcher Spotlight interview with Cameron.

Authors: Cameron Nemeth, William Gough, Paolo Segre, Frank Fish, Andrew Szabo, Wesley Fassmann, Scott Thomson, Martin van Aswegen, Julia Burrows, Ellen Chenoweth, Jacopo di Clemente, Ari Friedlaender, Jeremy Goldbogen, Malene Simon, Janice Straley, Simone Videsen, Fleur Visser, Caroline Weir and Lars Bejder

A solitary bubble-net feeding humpback whale lunging near the surface with its mouth fully agape, enjoying the large feast of herring trapped by its net. Credit: Martin van Aswegen (NOAA permit #19703)

Abstract: 

Maneuverability in cetaceans is facilitated by pectoral flippers, flukes, and spinal flexibility, features that are pronounced in humpback whales (Megaptera novaeangliae). Humpback whales exhibit several foraging tactics requiring high maneuverability not seen in other baleen whales, including bubble-net feeding. We hypothesized that the significant lift force produced by the humpback whale’s uniquely large pectoral flippers will result in them being the only species observed executing the tight, high-speed, sustained turns characteristic of solitary bubble-net feeding. To test this hypothesis, we used a combination of inertial sensor tag data and unoccupied aerial systems (UAS; drone) photogrammetry to quantify the turning performance of solitary bubble-net feeding humpback whales, and compared this to similar data from six other mysticete species. We found that solitary bubble-net feeding humpback whales exhibited centripetal accelerations (0.46 m s^-2) that exceeded the upper limit quantified in comparable turns by all six other mysticetes. This enhanced turning performance can be attributed to a substantial lift force generated by the humpback whale’s pectoral flippers (7,800 N ± 85 N), which contributes to centripetal acceleration and facilitates faster roll rates, allowing humpback whales to more quickly bank inwards and utilize their spinal flexibility to decrease their turning radius. Our findings demonstrate how humpback whales are uniquely adapted to exploit prey patches that might otherwise be insufficient for capture by animals of such a large size.

In an effort to expand the breadth of written text available in the Hawaiian language, Cameron also translated the abstract into Hawaiian, and had a Hawaiian language professor edit the translation. These collaborations support our local community, engage a broader audience, and remind all of the rich history and culture of the land on which we work.

Houluulu

Kokua ia ka huli ana o na cetaceans e ka eheu, hiu a me ka palupalu o ka iwikuamoo, ahuwale no keia mau mea i ke kohola (Megaptera novaeangliae). Hoike ke kohola i na ano alualu like ole he nui e koi ana i ka huli maikai ana i ike ole i na ano kohola ae, e like me ke alualu upena hua. Ua manao makou, ma muli o ka hue ae o ka ikaika nui na na eheu nui laha ole o ke kohola; aohe lua e like ai me ia hana. Penei noi na huli lii, awıwı, a wa loihi i laha ma ke alualu upena hua ponoi. I mea e hooia ai i keia manao, hoohana makou i ka mea paa ike a me ka pai kii ana o ka helekopa uila lii (UAS) i helu i ka maikai o ka huli ana o na kohola pakahi e alualu upena hua ana, a hoohalikelike ia me ka ike like o eono mau ano kohola. Oi aku ka hoohikiwawe poepoe o ke kohola (0.46 m s^-2) ma mua o ke kokı i helu ia no na huli like o na ano kohola like ole. Ma muli no o ka ikaika ae o ko ke kohola mau eheu (7800±85 N) ka maikai o ka huli ana, nana e hoonui i ka hoohikiwawe poepoe a kokua i ka wili wiki ana i mea e pelu ai i loko o ka poai a hoohana i ka palupalu o ka iwikuamoo i hooiki i ka lakou kahahanai. Kuhikuhi ka makou ike mai keia papahana noii i keia hua: maa ku kahi ke kohola i ke alualu ana i na kula ia i lawa ole paha no ka hopu ia ana e kekahi holoholona nui loa.

Study overview: 

Our team at the Marine Mammal Research Program joined up with our partner organization, the Alaska Whale Foundation, in Frederick Sound, Southeast Alaska to deploy non-invasive suction cup tags on solitary bubble-net feeding whales, and record concurrent morphological measurements using a drone. Over the course of a week, our team deployed tags on five individuals and documented 197 bubble-netting events. We calculated a suite of kinematics parameters (e.g., turn radius, centripetal acceleration, centripetal force) and compared our findings to a large dataset that had over 100,000 turns from seven different baleen whale species (including worldwide data from humpback whales) (Segre et al., 2022).

Dr. Will Gough deploying a Customized Animal Tracking Solutions (CATS; cats.is) tag on a humpback whale in Alaska. Credit: Alaska Whale Foundation (NOAA permit #19703)

The turning performance of these solitary bubble-net feeding humpback whales was extraordinary. The average diameter of the outermost bubble ring was 15.70 m, while the innermost ring measured just 9.92 m—smaller than the whales themselves. The tightest turn we recorded had a diameter of 6.50 m, only about 60% of the whale’s body length. Relative to their body size, the minimum diameter of the innermost ring was even smaller than the minimum length-specific turning radii of six of the seven dolphin species examined in Fish et al. (2002). Remarkably, the whales maintained an average swimming speed of 1.50 m/s across both inner and outer rings, meaning they didn’t slow down even as the turns became sharper. In the innermost ring, the average centripetal acceleration was 0.46 m/s², corresponding to a centripetal force of 11,585 N.

A video of a humpback whale producing a bubble-net from one of the CATS tag deployments. At the end of the video you can see the whale maneuver itself and lunge upwards through the middle of the net to engulf its trapped prey.

From the sourced dataset (Segre et al., 2022), we also found that none of the other species of baleen whales were generating the required amount of centripetal acceleration to create the innermost ring during their everyday behaviors. In other words, every other species of whale examined lacked the turning performance required to create the long duration, tight, high-speed turns that humpback whales regularly use in bubble-net feeding. While this is not necessarily reflective of the maximum potential of these species, and speculating on the performance ability of these species is difficult, this was in stark contrast to the humpback whale data from their study, where their humpbacks were achieving centripetal accelerations over three times the mean value used in solitary bubble-net feeding. This reveals two key insights. First, humpback whales are capable of significantly greater turning performance than what they typically employ during solitary bubble-net feeding, suggesting they operate well within their biomechanical limits. Second, even if other whale species were physically capable of producing a bubble-net, doing so would likely push them to the edge of their performance envelope, making it a biomechanically costly and impractical option for regular foraging.

Using the kinematic data from our five tagged whales, we modeled the lift force generated by average-sized pectoral flippers, which is about 6.10 m² in surface area on a 13.5-meter-long whale (Woodward et al., 2006). The result: roughly 7,800 N of lift generated by the pectoral flippers. During the tightest turns, a whale of this size would generate about 16,567 N of centripetal force, meaning their flippers could account for nearly half (47%) of the force required to turn. Using published data for a minke whale and a subadult fin whale (Cooper et al., 2008; Segre et al., 2022; Weber et al., 2014), we modeled their pectoral flippers’ contribution during turns at the same centripetal acceleration. The results show that minke flippers generated only about 10% of the required force and fin whale flippers a mere 4%. This stark contrast highlights that other baleen whales must rely heavily on alternative mechanisms such as using flukes as dynamic control surfaces, increasing bank angles and the flippers’ angle of attack, and employing more pronounced spinal flexion to produce the remaining lift needed for effective turning. As a result, whales lacking the pronounced morphology of large pectoral flippers would likely need to expend too much energy to execute tight turns efficiently, rendering foraging strategies like bubble-net feeding energetically impractical or unsustainable.

Baleen whales require dense aggregations of prey to make foraging energetically profitable, and because of their enhanced ability to maneuver, humpback whales are able to exploit less dense aggregations of prey that might otherwise be insufficient through the use of complex foraging strategies like bubble-net feeding. A big reason that they are able to create these bubble-nets is because they have these large, unique pectoral flippers that allow them to maneuver so efficiently at such a large body size.

Full citation: 

Nemeth, C., Gough, W. T., Segre, P. S., Fish, F. E., Szabo, A., Fassmann, W. N., Thomson, S. L., Van Aswegen, M., Burrows, J. A., Chenoweth, E. M., et al. (2025). The key to bubble-net feeding: how humpback whale morphology functionally differs from other baleen whales. Journal of Experimental Biology 228, jeb249607.

doi:10.1242/jeb.249607