We often think of stress as a bad thing, but it has evolved to protect us. When we find ourselves in life-threatening situations, our bodies prepare to fight or run. Stress hormones are released, our heart rate increases, our breathing quickens and our muscles become primed for action.
Every species on Earth has some form of stress response, from bacteria to plants, invertebrates and vertebrates. When faced with, for instance, being eaten, extreme weather or competition from rivals, the stress response kicks in and prepares individuals to get through the situation alive.
The behaviour that stress causes varies drastically between species, though. For example, while humans might run from a predator, opossums play dead and ooze a stinky liquid from their rear ends, horned lizards shoot blood from their eyes, and some plants create toxins so that they taste nasty.
Just as some people are more prone to stress than others, the same is true in animals. From fish to primates, individuals vary in how stressed they become. In some species, such as the white-faced capuchin, scientists have even shown that individuals who get more stressed are more likely to survive tough conditions. Stress really can be a good thing.
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