Are Humpback Whales and Killer Whales at War?

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In the early 1980s, scientists Hal Whitehead and Carolyn Glass of the Newfoundland Institute for Cold Ocean Science observed for the first time scientifically something that whalers had anecdotally described numerous times in the past: killer whales (orcas) attacking humpback whales. On two occasions, while sailing off the coast of Newfoundland in the North Atlantic, Whitehead and Glass witnessed a dozen or more orcas harassing large groups of as many as thirty humpback whales. What they saw drilled home the findings of a previous study published in 1980 – 33% of the 756 humpbacks identified off Newfoundland and Labrador had scars left by the teeth of orcas. Apparently, orcas and humpbacks frequently clashed.

Humpback whales can be fifty feet long and weigh 66,000 pounds, while killer whales average around twenty feet in length and tip the scales at 5,000 pounds for females and 10,000 pounds for males. With these massive figures in mind, Whitehead and Glass' dry description of the marine combat they saw seems a little more weighty.

"The orcas rushed towards the humpback at about 11-15 km/h," they wrote. "On four occasions we saw the humpback turn its belly toward the approaching orca, thrashing with its flukes. Fluke thrashing, turning, and rolling were common responses to orca attack. Directly after such an encounter, the orca retreated, frequently pursued for several meters by one or more humpback."

Glass and Whitehead described stringy pieces of blubber with flesh attached littered across the ocean battlefield, and numerous humpbacks bloodied with open wounds. No animals on either side were killed, however.

"During both encounters we had the definite impression that the orcas had no immediate intention of attempting to kill a humpback," they conjectured. "The orcas may have been simply attempting to obtain mouthfuls of humpback flesh. Alternatively, they might have been testing the humpbacks to single out animals which, perhaps on account of disability, sickness, or age, could then be killed by a greater number of orcas acting cohesively."

More than three decades later, scientists have now know that killer whales actively hunt humpback whale calves. This isn't too surprising. Orcas are often called the "wolves of the sea" because they regularly pursue large mammalian prey in packs. What is surprising, however, is that humpback whales – commonly viewed as gentle giants – seem to go on the offensive against killer whales. They fight back.

In 2016, a large team of scientists led by Oregon State marine ecologist Dr. Robert Pitman reported at least thirty instances all over the world of humpbacks attacking orcas as the orcas pursued other non-humpback mammals. On one incredible occasion, fourteen humpback whales intervened to prevent a pod of orcas from feeding on a gray whale calf the orcas had just killed.

Pitman et al

"One specific humpback whale appeared to station itself next to that calf carcass, head pointed toward it, staying within a body length away, loudly vocalizing and tail slashing every time a killer whale came over to feed," Alisa Schulman-Janiger, a whale researcher with the California Killer Whale Project, told National Geographic.

Another researcher remembered a similar instance.

“[W]e had 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... It seemed quite clear that the killer whale/gray whale interaction had attracted the humpbacks, though I cannot say whether it was motivated by curiosity, playfulness or an act of benevolence. The result however was that the gray whale cow/calf pair was able to escape. [On other occasions] I also personally observed several sea lions surviving predation attempts as a result of humpback whales distracting killer whales."

Behavior like this is not easy to explain. Did the humpbacks confuse the gray whale calves for their own, perhaps? Was it a bit of cross-species altruism? Or was it simply an antagonistic effort to deny the killer whales their meals – payback for previous predation attempts. Whale intelligence is prodigious but mysterious, so none of these hypotheses can be confirmed or refuted.

"The humpback whale is, to our knowledge, the only cetacean that deliberately approaches attacking mammal-eating killer whales and can drive them off," Pitman and his co-authors wrote.

They do this armed with by far the largest flippers of any cetacean. Each is up to five meters long, weighs as much as a ton, and "has a knobby leading edge often encrusted with large, sharp, sessile barnacles that can tear the flesh of their opponents," Pitman described. "When humpbacks are agitated by killer whales, they appear to randomly flail their flippers and flukes without specifically targeting individual attackers."

Killer whales, on the other hand, are armed with four rows of sharp, three-inch teeth, making this global 'war' between two of the most recognizable cetaceans a violent one indeed.

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