Humpback whales are gathering in huge groups, and nobody knows why

Although humpback whales are not typically known to be social creatures, preferring to swim alone or in small groups most of the time, experts have spotted so-called “super-groups” of the aquatic mammals during three recent research cruises, according to a new study.

Writing in the journal PLOS One, Ken Findlay of the Cape Peninsula University of Technology (CPUT) and his colleagues said that they had found 22 separate instances of between 20 and 200 whales gathering off the coast of South Africa during voyages in 2011, 2014 and 2015.

As Gizmodo and ScienceAlert reported this week, such large gatherings of humpbacks are rare. The creatures tend to prefer traveling in groups of seven or less. There had previously been only one recorded instance of a gathering of more than 20 whales, and that was thought to be multiple smaller groups traveling close together.

“I’ve never seen anything like this,” Findlay, a zoologist and marine biologist at CPUT, told New Scientist during an interview on Friday. “It’s possible that the behavior was occurring but just not where it was visible. Because there were so few of them, we may not have seen it.”

humpback whale in the water

Scientists aren’t sure of why these whales are behaving in this manner. Credit: NOAA

Odd behavior may actually be good news, say experts

In their study, he and his fellow researchers called the behavior “novel and intense,” adding that it is “a relatively recent behavior exhibited by these whales” and that no such large groups have been spotted “elsewhere in low or mid-latitudes during Southern Hemisphere… migrations.”

Findlay’s team believes that the whales may be adapting in response to the changing availability of prey, New Scientist said– and it isn’t just the size of their hunting groups that have gotten the attention of scientists. These “super-groups” were found far beyond the whales’ normal hunting grounds in the southern polar region of Antarctica, thousands of kilometers to the south.

Typically, Southern Hemisphere humpbacks (Megaptera novaeangliae) spend their summers in the Antarctic, eating krill and building up fat for the winter. Once the season changes, they head north to tropical and subtropical waters, where the females give birth to new calves. These large groups were spotted in October and November, indicating changes to their normal patterns.

“Reasons for this recent novel behavior pattern remain speculative, but may relate to increasing summer humpback whale abundance in the region,” the authors wrote. “These novel, predictable, inter-annual, low latitude feeding events provide considerable potential for further investigation of Southern Hemisphere humpback feeding behaviors in these relatively accessible low-latitude waters.”

In other words, the unusual activity may actually be good news. As ScienceAlert pointed out, Australia’s humpback population is reportedly at its highest levels since the 1960s, and whales have also become more abundant in South Africa, where nearly 100 years ago an estimated 90 percent of their population had been killed off by whaling, according to New Scientist.


Image credit: Jean Tresfon/PLOSone