Humpback whales are known for their lovely singing voices, not so much for their social skills. They are often loners, or typically hang out in pairs or small groups that don't stick together for very long.
But on three research cruises off the southwestern coast of South Africa over the past several years, researchers observed what they termed "super-groups" of whales feeding heavily. They noted between 20 and 200 whales in these large gatherings, which were documented in the fall of 2011, 2014 and 2015. Several casual observers also reported sightings by aircraft, estimating the whales' numbers at between 50 and 60.
“It’s quite unusual to see them in such large groups,” Gísli Vikingsson, head of whale research at the Marine and Freshwater Research Institute in Iceland, told New Scientist.
Southern Hemisphere humpbacks typically spend their summers dining on krill and building their energy reserves in high-latitude Antarctic feeding grounds, say researchers in their study released in the journal PLOS ONE. In winter, they head to the tropical and subtropical coastal waters of the Southern Hemisphere for calving and mating. Researchers were stymied as to why the whales showed a sudden change in pattern.
It's possible the whales were changing their habits due to prey and where it was available. There's also a chance they were merely returning to natural behaviors.
Humpback whales were observed feeding in the same area nearly 100 years ago but due to whaling, their numbers have dropped by about 90 percent.
“It’s possible that the behavior was occurring but just not where it was visible,” says Ken Findlay, lead author of the study from the Cape Peninsula University of Technology in South Africa. “Because there were so few of them, we may not have seen it.”