Do animals suffer from post-traumatic stress?
Every few years, snowshoe hare numbers in the Canadian Yukon climb to a peak. As hare populations increase, so do those of their predators, lynx and coyotes. Then the hare population plummets and predators start to die off. The cycle is a famous phenomenon among ecologists and has been studied since the 1920s.
In recent years, though, researchers have come to a startling conclusion – hare numbers fall from their peak not just because predators eat too many of them. There's another factor: chronic stress from living surrounded by killers causes mother hares to eat less food and bear fewer babies. The trauma of living through repeated predator chases triggers lasting changes in brain chemistry that parallel those seen in the brains of traumatised people. Those changes keep the hares from reproducing at normal levels, even after their predators have died off.