“Somewhere in the midst of the mammoth ocean; 

there exists the preposterously huge whale”

-Nikhil Parekh

 At the end of the whaling season of 1965, the first protections in American history were put in place for whales. From 1805 to that fateful day in 1965, whale populations are estimated to have collapsed from more than 125,000 individuals (possibly much more) to around 10,000 individuals (Clapham & Baker, 2017). Humpback whales, the 6th largest whales on earth, were hit particularly hard during the human whaling period due to their tendency to swim and hunt close to shore (Clapham & Baker, 2017; Lemon et al., 2021,). Eventually, demand for whales declined due to less need as a food source and medicine, and protections for them got stronger thanks to the International Whaling Commission. In 2021, humpback whale numbers were estimated to be around 80,000 in the southern hemisphere alone, with another estimated 32,000 in the northern hemisphere (Pirotta et al., 2021). As humpback whale populations continue to rebound, humans get more opportunities to study them, and we have been finding that These Creatures are complex beyond anything we imagined. 

Humpback whales are about 12-18 meters long in adulthood and can weigh up to  36 tons (Lemon et al., 2021). There is much speculation about the longevity of humpbacks. Many studies indicate a lifespan of up to 50 years, though there is evidence for humpbacks living 80 years or more (Clapham & Baker, 2017). Humpbacks are baleen whales, meaning they filter feed by opening their mouths wide and taking in massive amounts of schooling-organism-filled water and expelling the water out through long teeth-like bunches of hair called baleen, leaving the krill, lance, herring, or plankton locked inside the mouth to be eventually digested (Friedlaender et al., 2011). A single Humpback can eat 1,600 lbs of food a day at the peak of feeding season (García Cegarra et al., 2021).  This astounding feat of ingestion is the result of some very complex anatomical adaptations and hunting behaviors. 

Humpbacks are known as lunge feeders because of the way they dash upward toward the surface of the water through schools of fish with their mouths open (Kosma et al., 2019). However, their feeding behavior is much more varied and complex than just diving through a fleeing group of fish. Humpbacks around the world have been recorded performing a variety of feeding techniques, seemingly based on what prey they are hunting, including lunge feeding, net feeding, lobtail feeding, bottom feeding, flick feeding, and a variety of other techniques that are not so common as to have been named (Johnson & Wolman, 1984; Hain et al., 1995; Friedlaender et al., 2011; Lemon et al., 2021). During feeding season, which takes place about 5000 miles away from the breeding grounds, humpbacks use these techniques to feed for  up to 22 hours a day in order to put on as much weight as possible (D'vincent et al., 2017). It was long thought due to the empty stomachs of whales that die during the migration that humpbacks only ate when they traveled up north to the feeding grounds, but recently they have been sighted near Northern Chile and Ecuador during breeding season performing feeding behaviors in the warmer waters of the lower latitudes, (García Cegarra et al., 2021). Humpbacks are very adaptable and impressive hunters, but by far the most advanced technique in these whales' repertoire is one called bubble netting. 

Bubble netting, or bubble-net feeding, is an extremely complex behavior that is only known to be used by Humpback and Bryde’s whales. Bubble netting involves the use of air bubbles emitted from the blow hole, paired with spiral-shaped maneuvers to make prey swim in a denser formation for more efficient feeding (Friedlaender et al., 2011). This behavior was a mystery for a long time because scientists could only observe it from the surface of the water. But, in 2006 Friedlaender et al attached tracking/audio monitoring devices to humpbacks in Maine which were participating in bubble-net feeding behaviors. The results were revelatory. The team identified two main types of bubble-net feeding, which they called the double loop and the clockwise upward spiral.  Both maneuvers, seen in Figure 1, involved blowing bubbles out of the blowhole for the duration of the loop or spiral (Friedlaender et al., 2011). This motion through space, combined with the wall of bubbles created by the whale, creates a funnel structure around the schooling prey. This pushes them together into a tight mass just in time for the whale to surface with its mouth agape, capturing the condensed ball of fish in an extremely efficient manner (Friedlaender et al., 2011). The double loop maneuver involves a lobtail (violently striking the water surface with the tail fins) after the initial loop, known as the corral-loop, seemingly to stun the prey that have been collected at the surface, after which is the capture-loop where the whale opens its mouth and lunges through the now herded and stunned prey. The clockwise upward spiral technique involves the whale coming up from underneath the school of fish, spiraling up at an ever-sharper incline as it gets closer to the surface, and lunging at the top of the spiral with no stunning procedure like lobtailing involved. This study showed almost consistent variations between different individuals but rarely saw any variation in one individual’s techniques. Some whales use double loops almost every time, some favor the clockwise spiral. Of those humpbacks using the clockwise spiral technique, audio data showed that some prefer to make pillars of bubbles, blowing timed bursts that rise up to fit together, and others spiral upward making a constant stream of bubbles (Friedlaender et al., 2011). It is quite a surprise to see so much variation of this behavior in a single-feeding population. It has also been shown that Humpbacks in the gulf of Maine use a variation of this technique using “seltzer-sized” bubbles which are considerably smaller than those made by whales seen in Alaskan waters. This behavior shows even more variation in different populations around the world (Johnson & Wolman, 1984). Only one individual from this study conducted by Friedlaender, et al, showed some variation in bubble netting behavior, using the corral loop within a spiral net, essentially combining the two techniques, in 11 of 109 recorded events (Friedlaender et al., 2011).

 There are fascinating variations in netting behavior all over the globe and some scientists have even shown that they are culturally transmissible. Studies have noted bubble netting as a new behavior in British Columbia and in Chile, where the data goes back to the 1980’s and shows no signs of netting until recently (García Cegarra et al., 2021).  These findings changed the way people thought about the subject of bubble netting, but technology was still a major limiting factor. Computer models and drone technology have dramatically changed the field and given us insight into how bubble netting behavior involves precise use of sound and visual cues to make it a more effective hunting technique. 

Humpbacks have the longest pectoral fins-to-body length ratio of any whale, measuring up to one-third of the humpback’s body length, whereas many other cetaceans’ fins are closer to one-seventh of the body length (Kosma et al., 2019). Length of humpback fins has been correlated to increased agility, due to the ability to hunt faster prey than any other baleen whales, but it seems their fins supply them with more than just speed and maneuverability (Friedlaender et al., 2011). In 2019, a study was done by Kosma, Werth, Szabo, and Straley which proposes a very inventive use for the white underside of the humpback whales’ notably long pectoral fins. Using drones, the team filmed and photographed bubble netting events of individuals and discovered that they were using a technique never recorded before in humpbacks which they named ‘pectoral herding.’ Pectoral herding is the use of the pectoral fins, turned inward toward the mouth on either side to make a wall of white at the gaps in the mouth, seemingly to startle the fish away from the bright fins and make them condense in the center where the mouth will soon be, making for the largest possible mouthful for the whale. Interestingly, humpback whales seem to understand that this flash from the fins only works in bright light conditions. As can be seen in figure 2, pectoral herding is used in direct sunlight, but once the hunting ground is covered by shadows from the clouds, they change tactics to a simpler vertical lunge technique. However, the complexities of net feeding are many. It has been shown that humpbacks even employ the use of sounds when bubble netting, and this may be key to making the behavior possible. 

The most complex form of bubble netting is group netting, in which these whales employ all of the aforementioned tactics in a social setting. Humpbacks have been observed doing scaled-up versions of bubble netting, including unifying their vocalizations in order to sequester bigger schools of fish. Early studies found that each whale in the group has a role and does not deviate from it until the group dispels. They physically orient themselves to come up from the water in the same order every time for the duration of the feeding (D'vincent et al., 2017). Members of these groups still do the clockwise spiral motion, but they work together to make nets 20 meters in diameter or more (D'vincent et al., 2017). Some whales will even move in and fill in patches in the bubble wall, and some whales outright do not help build the net at all and just swim in to claim the catch (Friedlaender et al., 2011). This is potentially a case of cheating, as kin selection seems unlikely due to the humpback’s social system, namely behaviors like promiscuity, short parental period, and wide offspring dispersal (Friedlaender et al., 2011). However, cheating is rare, and usually, groups are highly coordinated. 

Bubble net fishing is a behavior that seems to get more complicated the more we learn about it. The more we know about these behemoths of the oceans, the more we can do to protect them. Scientists and most governments have been giving more careful attention to whales every year, and it is starting to show.

A study from 2021 recorded evidence of humpback ‘supergroups’ of 35+ individuals forming a bubble net together for the first time ever. This massive resurgence in humpback numbers may be due to the deep protections that have been enforced in waters around Australia, and the slowing in recent years of Japanese ‘research’ whaling in the southern oceans (Pirotta et al., 2021). It is possible that these behaviors existed in this area before whaling, but decimated populations did not warrant the techniques. It is also possible that it is another sign of cultural transmission of hunting techniques between humpback populations (Pirotta et al., 2021). More study is needed on the subject to find out, but the fact that there are enough humpbacks in the southern oceans to conduct these kinds of studies for the first time since the early 1800’s is very heartening. 

Populations are bouncing back from near extinction, revealing proof that humanity has the power and ability to be good stewards of the earth. The resurgence of humpback wwhales is kind of a small thing in the grand scheme but is also a great source of hope in the sometimes dark landscape under which climate change looms. Maybe if we are capable of protecting the whales, we are capable of protecting the biodiversity of our planet.

References

Bryngelson, S. H., & Colonius, T. (2020). Simulation of humpback whale bubble-net feeding models. The Journal of the Acoustical Society of America, 147(2), 1126–1135. 

Clapham, P. J., & Baker, C. (2017). Whaling, modern. In Encyclopedia of marine mammals (pp. 1070–1074). Elsevier. 

D'vincent, C. G., Nilson, R. M., & Hanna, R. E. (2017). Vocalization and coordinated feeding behavior of the humpback whale in southeastern Alaska. Environmental science. Retrieved October 5, 2022, 

Friedlaender, A., Bocconcelli, A., Wiley, D., Cholewiak, D., Ware, C., Weinrich, M., & Thompson, M. (2011). Underwater components of humpback whale bubble-net feeding behaviour. Behaviour, 148(5-6), 575–602. 

García Cegarra, A. M., Castro, C., & Van Waerebeek, K. (2021). Feeding of humpback whales in low latitudes of the southeast pacific ocean. Neotropical Biodiversity, 7(1), 421–430. 

Hain, J. W., Ellis, S. L., Kenney, R. D., Clapham, P. J., Gray, B. K., Weinrich, M. T., & Babb, I. G. (1995). Apparent bottom feeding by humpback whales on stellwagen bank. Marine Mammal Science, 11(4), 464–479. 

Johnson, J. H., & Wolman, A. A. (1984). The humpback whale, Megaptera novaeangliae. Marine Fisheries, 46(4), 30–37. Retrieved October 12, 2022, 

Kosma, M. M., Werth, A. J., Szabo, A. R., & Straley, J. M. (2019). Pectoral herding: An innovative tactic for humpback whale foraging. Royal Society Open Science, 6(10), 191104. 

Lemon, C. L., Cheyne, S. A., & Werth, A. J. (2021). Megaptera novaeangliae Bubble Net Feeding Behavior: A Brief Review. H-SC Journal of the Sciences, 10. 

Parekh, N. (2016). poems (1st ed.) [PDF]. Poemhunter. 

Pirotta, V., Owen, K., Donnelly, D., Brasier, M. J., & Harcourt, R. (2021). First evidence of bubble‐net feeding and the formation of ‘super-groups’ by the east australian population of humpback whales during their southward migration. Aquatic Conservation: Marine and Freshwater Ecosystems, 31(9), 2412–2419.