I find the final question about human intervention fascinating.

  The scientists aren’t recommending intervention, even if the perpetrators tend to be the same few individuals. “We don’t know how natural it is,” says Ursula Siebert, a veterinary pathologist specializing in wildlife population health at the University of Veterinary Medicine Hannover who was not involved with the work. “It can definitely be hard to watch,” Langley adds. “But the life of a seal—and indeed any wild animal—is tough.”

This idea that human influence over nature should not reach beyond species boundaries, that there is no universal value common to several species, seems prevalent in natural sciences. Is it coming from an understandable but misleading distrust of human society and idealisation of "nature", or from a deeper understanding that "nature always knows better", I can't decide.

I once lived in an apartment in Colorado with a balcony overlooking a pond. Once a grebe was paddling around in it followed by four chicks. It was a great image for the Colorado Tourism Office. Then mamma grebe swam back and swallowed the fourth chick whole, and the smaller family paddled away.

Brood reduction isn't common in grebes, but I saw it anyway, and thought maybe I didn't get the straight dope from Disney movies growing up.

I am curious why the killers didn't eat more. Is this just the choicest bits - another pup is easy to find?

Perhaps this is somewhat like male lions killing cubs that are not immediately theirs? Do the seals kill their own pups? Difficult to study, I guess.

Oddly enough, I've seen a similar injury on a dolphin before. Well, the head was missing, but the cutoff point could be described as "corkscrew". None of us had a good idea of the cause, but this hints it may have been predation or scavenging.

The ending reminds me of the “Americans are obsessed with protein” article

Ah, nature thats more like it. Less wholesome, more cthullu.