A humpback whale breaches at Uramba Bahia Malaga National Natural Park in Colombia. © Dan Kitwood/Getty
The relationship between humpback whales and orcas is tense to say the least, which is unsurprising given the orcas’ taste for humpback calves. The humpbacks vigorously defend their calves from attacks, but they also extend that protection to other species of sea mammals.
A new review of 115 historical observations of interactions between the two species reveals that it’s not uncommon for humpbacks to attack hunting orcas in much the same way that songbirds mob raptors.
It makes perfect sense for humpbacks to drive off predators that threaten their offspring. But in only 11 per cent of observations was it a humpback calf that was being hunted. The rest of the time, the target was a seal, sealion, another whale or dolphins, or even, on one occasion, a sunfish.
In one striking encounter an adult humpback rescued a seal that had been knocked from an ice floe by orcas, by raising it out of the water on its belly and holding it in place with its fins. Humpbacks have been observed protecting their own calves in this way.
While it may be tempting to credit the whales with something resembling human morality – an urge to protect the weak from the strong, perhaps – Robert Pitman of the US National Oceanic and Atmospheric Administration (NOAA) is reluctant to anthropomorphise the animals. He believes this apparently altruistic behaviour can be explained in terms of self-interest.
“I don’t think that humpback whales have moral codes,” he told BBC Wildlife Magazine. “My guess is that they are just focused on preventing killer whales from having their way during attacks, regardless of what the prey species may be.”
In which case, the other species to which the humpbacks extend their protection benefit as a side effect of the whales’ simple rule of thumb.
“The behaviour can persist because it is the net results that pays off for the humpbacks,” said Pitman. “And adult humpbacks are not at risk of predation from killer whales, so the cost of them intervening is rather small.”
Source: Marine Mammal Science.
Read more wildlife news stories in BBC Wildlife Magazine