Humpback whales have scientists stumped. These whales are changing their typical behavior and have begun forming groups of approximately 200 whales or more. Typically, humpbacks are found alone, in pairs, or in small groups. But something has prompted the whales to alter that pattern.
These massive groups weren't a one-off occurrence, and have been spotted several times over the years. Research crews observed the large groups during cruises in 2011, 2014, and 2015. The groups were located off the south-western coast of South Africa.
But the fact that the groups converged wasn't the only unusual factor here. When the whales were spotted, they were much further north than their normal feeding grounds. Typically, whales feed in the polar Antarctic waters during the summers. They spend winters in tropical latitudes.
These super groups of whales were the subject of a recently published study. The study, published on PLOSone, examines the convergence of groups of between 20 and 200 whales. It notes that these Southern Hemisphere humpback whales were observed feeding in these huge groups.
At this point, the exact reason why the humpbacks are changing their behavior is unknown. “I’ve never seen anything like this,” said Ken Findlay, lead author on the study. The whales have the scientists stumped.
It's possible that the Humpbacks are simply repeating a behavior that's more than 100 years old. Humpbacks were once seen feeding in the same area off of South Africa, though that was almost 100 years ago. Whaling dramatically reduced the whales' population, so the behavior may have been going on all of these years but wasn't visible because the whale population was so low.
The humpbacks may also be modifying their behavior in response to changes in the prey that's available. Whale congregations often indicate areas of the ocean that are particularly productive. After all, food has to be dense and plentiful in order to support multiple whales.
These massive congregations definitely had a purpose: to feed. Scientists observed the whales repetitively and consecutively diving. The whale blows had a fishy smell to them. Clearly, the whales were hunting.
Humpback whales hunt for their prey. They gang up on schools of fish using a technique called "bubble net feeding." The whales circle their prey, with some whales blowing air so that other whales can drive the prey into a net that's been made out of bubbles. The fish get confused and trapped inside this bubble net, and then all of the whales rush in and eat the fish.
It makes sense that humpbacks congregate in areas where the feeding is good. They have to, as these massive whales can eat up to one ton of food a day, each. If the availability of the whales' prey is increasing, then they may be congregating more than they have in the past. It's possible that humpbacks once used to form these massive groups, and that they just haven't been able to because the prey hasn't been concentrated enough.
Because humpbacks spend so much time alone, they don't all participate in bubble net feeding. Whales are capable of capturing prey on their own, and bubble net feeding is a learned behavior. But during the times when whales are in groups, whales can feed efficiently.
The fact that we're seeing these huge humpback groups may have a positive implication for both the species and the health of the seas. Gísli Vikingsson, head of whale research at the Marine and Freshwater Research Institute in Iceland, noted that the humpback whale population has seen a recent resurgence. “For the last few decades, suddenly they seem to have overcome some threshold and have begun to increase very fast,” said Vikingsson. It's possible that these massive groups are just a reflection of the whales' natural behavior, made possible by the increased numbers.
Will we ever understand all of the marvels of the ocean? Probably not. The mystery of these huge whale gatherings certainly requires more investigation. Until we know the answer as to why these groups are forming, though, we can rejoice in seeing that the humpback whale population is thriving today.