COS 184-3 - Effects of predation risk on learning and memory in free-living mammals

Background/Question/Methods

Predators can influence prey in two non-exclusive ways, through consumptive effects, where the predator influences the density of prey by direct consumption, and through non-consumptive risk effects, where the presence of the predator can alter aspects of prey physiology, morphology, and behaviour. One such consequence of predation risk effects found in laboratory studies is an impairment of learning and memory. However, in free-living animals learning and memory have been suggested to be essential to their ability to respond to and cope with environmental stressors. Yet, few studies have examined the cognitive ability of free-living animals when exposed to predation risk. Here, we used a modified version of Morris Water Maze (MWM) to test how predation risk affects cue-based spatial learning and memory in free-living white-footed mice (Peromyscus leucopus). Free-living mice were first exposed to auditory playbacks of predation risk or control sounds for 3 weeks. They were then live-trapped and subjected to the MWM test, which consisted of mice being placed into a small pool of opaque water where they needed to find a hidden platform to escape the water. They underwent 5 consecutive trials (learning), followed by a 2 h rest period prior to the last trial (memory).

Results/Conclusions

Contrary to lab-based studies, we found that predation risk had no effect on mice learning; i.e., they maintained their ability to learning (reducing the distance traveled to find the platform across the first 5 trials). We did find that risk exposure impaired memory; i.e., a loss of performance between the 5^th and 6^th trial. These results support the idea that learning may be of critical importance for free-living animals in coping with environmental stressors (opposite of laboratory findings). However, predation risk did reduce their ability to remember (similar to laboratory findings). Examining risk-induced effects in free-living animals may provide novel insights into cognitive behaviour and neurobiology, given that these animals have evolved with such stressors.