The killer whales that feed on mackerel have been found to have very worn down teeth as a result of their feeding behaviour.

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Although we can't say for sure if it is this early exposure to these foods that makes the difference or whether it is learned behaviour from the feeding habits of the whole family that is important, it makes sense that fresh is best.

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"They're going there to feed, or they're going there for meeting, where males and females could meet perhaps away from a feeding area, where there's less competition and more focus on mating behaviour, " he suggested.

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