How does recent experience with predators affect learning ability in mosquitofish?

Stressful experiences can alter how an individual views the world, such as whether it is a safe or dangerous place. The level of risk an individual perceives can then affect an individual’s behavior in a variety of... [ view full abstract ]

Stressful experiences can alter how an individual views the world, such as whether it is a safe or dangerous place. The level of risk an individual perceives can then affect an individual’s behavior in a variety of contexts. For example, the presence of a predator nearby can cause individuals to group more closely together and show more vigilance. Using the local western mosquitofish (Gambusia affinis), this study examined whether recent brief encounters with predator cues can affect an individual’s ability to learn a color-reward association. Mosquitofish were either exposed to visual and chemical cues to predation pressure briefly twice a day for two days (predator-exposed treatment) or exposed to control water cues twice a day for two days (control treatment). After their treatment, all mosquitofish were trained in pairs to associate entering a doorway in a particularly colored wall with a food reward. Pairs had two training sessions a day over the course of 3 days and during each session, we recorded the time with which they entered to rewarded doorway. Our results suggest that repeated encounters with predator cues results in learning deficits. Individuals from the predator-exposed treatment were slower to enter the rewarded chamber to get the food reward compared to control individuals. A subset of individuals were tested 4 days later to determine whether they retained their learned association and the difference between predator-exposed and control treatments in their color-reward association persisted  through this extended time period. These results suggest that recent stressful encounters affect either an individual’s ability to learn a color-reward association or their motivation to explore (either to enter a doorway or obtain food). Understanding how previous stressful experiences can carry over to affect other behaviors is important to how we view vulnerability of individuals to disturbance.