After reviewing over 100 interactions between humpback whales and killer whales, researchers have found that not only do humpbacks aggressively protect their own calves from killer whales, they also tend to rush to the aid of other distraught species like seals.
A humpback might be able to fight a killer whale because of its gigantic size and massive flippers, researchers say.
One possible reason for the humpbacks’ seemingly selfless act could be to increase the chance of protecting their own calves from killer whales. Sometimes this ends up protecting other species.
In 2009, two marine biologists — Robert Pitman and John Durban — observed a series of strange events enroute to the Antarctic Peninsula: humpback whales would rush in to rescue seals that were being attacked by killer whales.
In one instance, for example, a pod of ten killer whales (or orcas) dislodged a crabeater seal from an ice floe. Immediately, two humpbacks charged in and began swimming around the floe. They kept bellowing loudly through their blowholes and slapped the water with their tails and giant flippers until the killer whales “seemed annoyed and finally left the seal alone,” Pitman and Durban write in Natural History.
Now, in a review study published in Marine Mammal Science, Pitman and his colleagues have found that these were not isolated incidents. After reviewing over 100 interactions between humpback whales and killer whales, the team concluded that not only do humpbacks aggressively protect their own calves from killer whales, they also frequently rush to the aid of other distraught species like seals. Even lone humpbacks have been observed meddling with large groups of killer whales that were attacking other species.
In fact, the humpback whale may be the only cetacean that deliberately approaches attacking killer whales and can drive them off, the authors write.
“Many people had seen humpback whales interfering when killer whales attacked other species, but it had previously been largely unreported,” Pitman, who works with the U.S. National Oceanic and Atmospheric Administration’s (NOAA’s) Fisheries Service in San Diego, California, told Mongabay. “A lot of people expressed disbelief in what they had witnessed and I think that may have prevented them from reporting their observations in a formal way.”
The researchers speculate that a humpback might be able to win against a killer whale mainly because of it’s gigantic size and massive flippers, which can measure up to five meters long. In fact, humpbacks have the largest flippers among all cetaceans, the authors write, that are also very flexible and maneuverable.
“When humpbacks are agitated by killer whales, they appear to randomly flail their flippers and flukes without specifically targeting individual attackers,” the authors add. “Nevertheless, killer whales appear to recognize the danger and normally remain ‘at arm’s-length’ when interacting with humpbacks.”
But why would a humpback rescue another species from killer whales, especially when doing this can be both time and energy-sapping, and potentially dangerous?
The answer remains unclear. But one possible reason for the humpbacks’ seemingly selfless act could be to increase the chance of protecting their own kind from killer whales.
This is because adult humpback whales are usually safe from killer-whale attacks because of their gigantic size, but their calves and juveniles are not. So whenever humpbacks hear killer whales hunting or fighting, they could preemptively be interfering with them in the hope of saving members of their own families, the researchers believe. Sometimes, their interference inadvertently benefits other species.
“Humpback calves tend to return to their mother’s feeding and breeding grounds over their lifetimes,” Pitman explained. “That means that there is some increased likelihood that nearby humpbacks will be related and this could explain why humpbacks converge to interfere when killer whales attack other humpback calves – they may be family. When they do this, humpbacks may instinctively respond to attacking killer whales without regard to the species being attacked, which could allow other species to sometimes benefit. This can work because, due to their very large size, healthy adult humpbacks have little to fear from killer whales, so that the cost of intruding is minimal. It is the net gain to humpbacks that can allow this to happen.”
However, whale behavior remains little-understood, researchers say. This is mainly because commercial whaling in the 20th century depleted most oceans of large whales, leaving behind huge gaps in our knowledge of whales.
“Nearly all whales are still recovering from the devastation of 20th century whaling,” Pitman said. “As their populations continue to recover (to the extent that they will), we will learn even more about the behavior and ecological impact of these very large animals. We may be in for even more surprises as we have seen with humpbacks and killer whales.”
- Pitman, R. L., Deecke, V. B., Gabriele, C. M., Srinivasan, M., Black, N., Denkinger, J., Durban, J. W., Mathews, E. A., Matkin, D. R., Neilson, J. L., Schulman-Janiger, A., Shearwater, D., Stap, P. and Ternullo, R. (2016), Humpback whales interfering when mammal-eating killer whales attack other species: Mobbing behavior and interspecific altruism?. Mar Mam Sci. doi:10.1111/mms.12343