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I am reading Three Among the Wolves by Helen Thayer, who is best known for walking and skiing to the North Magnetic Pole accompanied only by her husky, Charlie.

In a subsequent trip, she and her husband spent nearly a year observing the behavior of three wolf packs in three different parts of Canada. This question is about the pack observed on the ice of the Beaufort Sea, to the northwest of Tuktoyaktuk, in winter. (In spring, the wolves move back to land.) This pack of wolves scavenged off the kills of polar bears. As Thayer says:

Polar bears, the primary hunters, killed the prey [the seals] and then ate mostly the fat. Wolves and foxes then ate the remainder of the seal.

According to the National Geographic Society's article Scavenger, scavengers are the janitorial staff of the ecosystem:

Scavengers play an important role the food web. They keep an ecosystem free of the bodies of dead animals, or carrion. Scavengers break down this organic material and recycle it into the ecosystem as nutrients.

The incident that Thayer describes was not about scavenging, but about wolves as recipients of the largesse of a polar bear:

...The bear thrust his head into the seal hole...He hauled out a thrashing seal, crushed its head, and without stopping to eat, walked to the edge of the ice and stared into the water. The three wolves....[rushed] to the body.

The bear ate none of this kill.

On reading the first quote, I postulated that the bear ate only the blubber because it was more efficient to capture another seal, rich in blubber, than to pick at the meat; the wolves were simply filling a niche by scavenging the bear's leftovers, as were the arctic foxes who also followed the bears on the ice.

But it is harder to explain the bear's behavior in the second quote. This seems like pure altruism on the part of the bear (which seems unlikely), or an isolated incident. So, my question:

Has this "altruistic" behavior been reported in other sources for polar bears -- or for any large predator with respect to scavengers -- and if so, what benefit does the polar bear (or other large predator) gain from it?

Addendum: Possibly pertinent facts prompted by comment by @Chris H: The wolves on the sea ice numbered eleven, one of whom had an injured paw. The wolves seemed to belong to a single pack. However, only three wolves were in attendance on the "donor" bear. There were at least six polar bears spread out along the ice margin. The wolves waited respectfully for the bears to leave their kills before darting in. The "donor" bear in question deliberately walked away from his untouched kill, turned his back on it, and stared into the water, allowing the wolves free and unthreatened access to his kill. Also of note is that a bear will sometimes share food with another polar bear. See this report. There is an etiquette for asking. Also, Wolves sometimes predate on small polar bear cubs.

I am not getting far in my research. Most biologists agree that altruism exists among members of the same species for mutual survival reasons, but not between members of different species. Some evidence that this is too shortsighted appears sporadically, e.g. in this article about whales and dolphins helping each other, about a leopard taking care of a baby baboon and wolf/raven research.

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    It's not unknown for scavengers to drive off primary hunters (I'm sure I've read about hyenas and lions in this context). While that doesn't assist to be the case here that bear's experience with wolves may have led it to back off. Conflict (leading to learned behaviour) is more likely as when they meet its likely to be when one or both species are at the edge of normal conditions, and so more likely to act desperately. Comment as speculative, but I'll try to find sources for an answer
    – Chris H
    Feb 7, 2019 at 6:50
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    Contra to some beliefs some animals just like to kill ranker.com/list/animals-that-kill-for-no-reason/laura-allan Feb 7, 2019 at 19:24
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    Maybe the bear just didn't like the taste of that particular seal.
    – B540Glenn
    Feb 8, 2019 at 14:37
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    @JamesJenkins the article that you link is a bit... "sensational". I'm not sure it makes a good source of information although it does have some potentially credible citations.
    – llama
    Feb 13, 2019 at 9:25
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    The seal had a crushed head. Even bears know the warning, "Do not consume if seal is broken.". Nov 19, 2019 at 14:23

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A possible explanation is the wolf-raven interactions described in this question.

Ravens and wolves share kills. Ravens will descend almost immediately after -- sometimes even before -- the wolves make their kill. The author of the book referenced in the above question postulates that ravens can lead wolves to large prey (for example, moose) and receive a payoff in meat. A similar cooperation may be operating between wolves and polar bears. The weak point in this argument is that while ravens can scout over much greater distances than can wolves, the same is unlikely to be true of wolves with respect to polar bears.

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