Altruists of the ocean?
Recent accounts and Internet videos suggest that humpback whales will approach marine animals in distress and offer protection, most notably when the animals are being attacked by killer whales. This seems like a particularly bad idea on the part of the humpbacks because it puts them at elevated risk of becoming the killer whales’ next victim.
After witnessing one of these acts off the coast of Antarctica, in which a pair of humpbacks came to the rescue of a Weddell seal who was being pursued by killer whales, marine ecologist Robert Pitman of the National Oceanic and Atmospheric Administration’s (NOAA’s) Southwest Fisheries Science Center in California wanted to learn more about this seemingly altruistic behavior.
Pitman and his team combed through reports of observed run-ins between humpbacks and killer whales made by passengers on whale-watching boats and researchers between 1951 and 2012.
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They found that humpbacks almost always interacted with mammal-eating killer whales, only rarely encountering fish eaters. Further, the humpbacks were usually the ones to approach the killer whales and not the other way around.
When a humpback approached, the killer whale was often in the midst of attacking or feeding on a victim. Sometimes these victims were other humpbacks, but their prey also included minke whales, sea lions, seals, and fish. On many of these occasions, the humpbacks displayed distinctive flipper slapping and side-to-side slashing behaviors.
In their paper, published in the journal Marine Mammal Science, the researchers highlight quotes from some of the people who witnessed the interactions. One observer describes having “traveled quite a distance to observe a group of killer whales attacking a gray whale mother and calf pair and out of NOWHERE, a humpback whale came trumpeting in followed by another and then another until we had about 5 or more humpbacks in the immediate area.”
To this observer, it was clear that the clash between the killer whale and gray whale is what had attracted the humpbacks, and the result of the intervention was that “the gray whale cow/calf pair was able to escape.” Other witnesses to these sorts of scenarios had similar impressions.
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On the face of it, the apparent defense of other species by humpback whales seems like altruism — the humpbacks derive no obvious benefits from their interventions and in fact put themselves at considerable risk by getting involved.
However, the authors believe it may simply reflect the humpbacks’ predisposition to throw themselves into the ring when killer whales attack their own calves. Rather than trying to discern who the victim is each time, the humpbacks automatically respond whenever they sense a killer whale is on the attack.
“I think they just have a simple rule,” Pitman tells Science News. “When you hear a killer whale attack, go break it up.”
Watch this video of humpbacks interrupting a killer whale attack on a gray whale calf:
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