Humpback whales intervene in orca attacks against other species

Humpback whales have been making the news for their organized “rescues” — seemingly heroic efforts in which the humpbacks have intervened in attacks by killer whales against other marine mammals.

The humpbacks have not only protected their own calves but they have gone well out of their way to protect gray whales, minke whales, Dall’s porpoises, Steller sea lions, California sea lions, Weddell seals, crabeater seals, harbor seals, northern elephant seals and even ocean sunfish, according to researchers.

The latest incident, in which humpbacks reportedly intervened in a killer whale attack on a Steller sea lion, is said to be the first reported incident in the Salish Sea. The incident took place last week off Sooke, BC, about 20 miles west of Victoria.

“What we witnessed was pure aggression,” Capt. Russ Nicks of BC Whale Watch Tours of Victoria said in a news release from Pacific Whale Watch Association. “We had four humpbacks trumpeting, rolling on their sides, flukes up in the air multiple times.

“The killer whales split many times into two groups, with one that appeared to try to draw the humpbacks away from the sea lion. The other group would go in for the attack while the humpbacks were safely away – but then they’d get in the middle of it again, fighting the orcas off. It was amazing to watch.”

These killer whales were of the transient variety, a subspecies of killer whales that eats marine mammals, as opposed to the resident orcas that each fish.

The same attack and rescue was viewed by naturalist Alethea Leddy of Port Angeles Whale Watch Company, as reported in the news release:

“We got there in time to see some crazy surface activity, with humpback whales splashing in the distance along with orcas. Then two humpbacks surfaced next to us trumpeting, and the next thing we know there were four humpbacks, possibly six, all defending the sea lion.

“The water boiled all around as the orcas tried to separate the sea lion from the humpbacks. It was a wild scene, with the humpbacks even circling the sea lion trying to keep him safe while he frantically struggled to get his breath.

“The anxiety of the humpbacks was palpable, and they took turns diving and slashing at the orcas. This life-and-death drama went on and on until the four transient orcas, known as the T100 family, moved off in the distance. As they did, we saw the sea lion appear next to the humpbacks being guarded and escorted in the opposite direction.

“This was an unbelievable encounter. Hats off to our courageous humpbacks and best wishes to our little Steller sea lion, survivor for another day!”

In July, 14 marine mammal experts reported on 115 apparent rescue efforts by humpback whales during what appeared to be killer whale attacks on other species of marine mammals. Their report appeared in the journal Marine Mammal Science.

Reasons for these rescue efforts are open to much speculation, but the researchers noted that evidence is mounting in favor of a belief that killer whales that eat marine mammals, called MEKW, attack young humpback whales more often than commonly reported.

“Clearly, MEKW predation, even if rarely observed and targeting mainly calves and subadults, represents a threat to humpbacks that is persistent, widespread, and perhaps increasing,” the report states. “As such, humpbacks could be expected to show some specific anti-predator behaviors, and indeed some have been suggested. Ford and Reeves (2008) summarized the defensive capabilities of baleen whales faced with killer whale attack, and they identified two general categories of response.

“Balaenopterid rorquals (including fin whales and minke whales) use their high speed and hydrodynamic body shape to outrun killer whales and were classified as flight species. The generally more rotund and slower-swimming species — right whales, bowhead whales, gray whales and humpback whales — apparently rely on their bulk and powerful, oversized appendages (tail and flippers) to ward off attackers. This group was categorized as fight species.”

Of course, it is one thing for the humpbacks and other baleen whales to take a defensive posture. It is quite another thing for them to go after killer whales when another species of marine mammal is under attack.

In the report, humpbacks initiated encounters with MEKWs 58 percent of the time, while the killer whales initiated contact 42 percent of the time — at least for those cases when the killer whale ecotype could be identified as marine mammals eaters. On a few occasions when known fish-eating killer whales were involved, the encounter was relatively benign, the researchers said.

The video, shot by BBC filmmakers, show a pair of humpback whales attempting to prevent a group of orcas from killing a gray whale calf. In this case, the effort was unsuccessful.

When humpbacks went to the rescue of other marine mammals, it appears that the rescuers were generally a mixture of males and females, according to the report. Humpback postures, whether attacking or defending, involved slapping their flukes on the surface, slashing from side to side, bellowing, persuing and flipper slapping. The length of battles reported ranged from 15 minutes to seven hours. In the end, the prey that was at the center of the battles was killed 83 percent of the time — at least for those cases when the outcome was known.

“The humpback whale is, to our knowledge, the only cetacean that deliberately approaches attacking MEKWs and can drive them off, although southern right whales may also group together to fend off MEKWs attacking other right whales,” the researchers stated, adding that humpbacks’ powerful flippers covered in sharp barnacles can shred the flesh of their opponents.

When in hunting mode, transient killer whales are generally silent, not making much noise. Once an attack begins, they become more vocal, perhaps to coordinate the attack. It appears that humpbacks respond to killer whale vocalizations from distances well out of sight of the attack.

The reasons the humpbacks would get in a fight with killer whales to save another species are listed in three categories:

• Kin selection: Protecting an offspring or closely related animal.
• Reciprocity: Protecting unrelated animals, generally as part of a social organization.
• Altruism: Benefitting another animal at some cost to the one taking action.

It is possible, the researchers conclude, that humpbacks could be improving their individual and group fitness to fend off attacks against their own by protecting other species. One idea is that the killer whales may think twice about attacking a humpback of any age.

“We suggest,” they write, “that humpbacks providing benefits to other potential prey species, even if unintentional, could be a focus of future research into possible genetic or cultural drivers of interspecific altruism.”

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