SURVIVAL OF THE STRESSED

Abstract

A nearby predator eyeing you up for their next meal is undoubtedly enough to kick-start a stress response in all but the very coolest of us – after all, who wants to be eaten? And although stress can bring with it many disadvantages, in the face of a hungry predator it could mean the difference between life and death, and is thought to cause the famous fight-or-flight response. However, in recent years it has proved difficult to directly link the stress response with a change in behaviour, and in some animals the stress response seems out of sync with the behavioural response. As stress responses in animals can be quite complex, Shelley Adamo, from Dalhousie University, Canada, decided to turn to the simpler cricket to see whether their stress response caused a change in behaviour (p. 4608).To begin with, Adamo, along with the help of undergraduate students Ilya Kovalko and Brianna Mosher, allowed crickets to wander around a cross-shaped maze free from any threats. Two of the arms were covered in black board to provide shelter, and the team then recorded how long the crickets spent in both the open and sheltered areas.Next, the team wanted to induce a stress response in their crickets. To do this, the trio exposed some of their crickets to a moving robotic toy hamster that mimicked a potential predator. They also injected some of their crickets with octopamine, a stress response chemical very similar to noradrenaline. After placing the crickets back in the cross-shaped maze, the team found that crickets that had been previously stressed by the moving robotic hamster or those that had been injected with octopamine spent more time hidden in the sheltered areas than before their stress treatment.To test how the stress response may help in a real-life predator–prey situation, the team next placed their crickets into an open maze setup alongside an additional participant – a bearded dragon with a taste for crickets. They found that crickets that had been previously stressed were much less likely to be eaten than their unstressed friends, who often froze in the open, making them an easy target for the hungry bearded dragon. So being stressed does help sometimes!