In this situation, you're not really running away from the bear.
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At first glance, this small fish looks pretty innocuous, and many people in South America keep them as pets.
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If you're being chased by a hungry bear, you're more likely to escape if you have a friend running alongside you.
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Small fish often protect themselves by swimming in large groups, making it hard for predators to target a specific fish.
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It could be worse. You could try to trip your friend up or even break their leg, except you're probably too decent to do that.
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That way, the bear might kill your friend instead of you.
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You're just trying to run faster than your friend.
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To their surprise, they discovered that the astyanax bimaculatus turned on each other if a predator approached.
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However, they are a bit of a nuisance. "There's a big problem with fish entering hydroelectric power station machinery. "says Robert Young of the University of Salford in the UK."
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So a few years ago, Young and his fellows started investigating ways to deter the fish from getting into the machinery.
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But a South American fish has no qualms.
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Young says other species might betray each other in the same way, but perhaps nobody has managed to ob-serve this behaviour yet. Thank you.
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In theory, all animals that could become prey have an incentive to attack their fellows when the group is threatened.
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