Science news this week was full of bizarre and baffling animal behavior, with news of chewed-up orca fins washing up on a Russian beach pointing to cannibalism among the apex predators.

There are several orca subspecies, and scientists initially thought these groups kept mainly to themselves. But genetic evidence alongside distinct tooth marks heavily suggests that one group may occasionally snack upon the other, which could explain why the preyed-upon orcas live in large, tight-knit groups.

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