Experience with predators shapes learning rules in larval amphibians

Abstract

Experience is essential for many prey species that must learn about predation risk to survive and reproduce. How prey incorporate information about predation risk via multiple learning events has been the subject of several studies, but results have been inconsistent, with cases where multiple conditionings have enhanced or weakened the learned responses. We hypothesized that such different outcomes reflect differences in the timing and frequency of past experience with the predator. To test this hypothesis, we provided naive wood frog tadpoles (Lithobates sylvaticus) with 4 days of experience with a predator. After a short (2 days) or longer (17 days) delay, tadpoles (naive or experienced) were conditioned to recognize the predator 0, 1, or 6 times. When tested the following day, all tadpoles from the short-delay group exhibited similar intensities of learned responses following 1 or 6 conditionings. However, a different pattern emerged when their background and recent experiences were separated by the longer time lag. Naive tadpoles responded similarly following the conditionings, but experienced tadpoles exhibited stronger responses after receiving multiple conditionings. We confirmed our hypothesis again using wild-caught tadpoles that had predator experience in their natural environment. Our results provide new insight into the surprisingly sophisticated learning rules for how certain aspects of past experience dictate the intensity of learned responses in tadpoles. These results also shed light on conflicting outcomes of past studies and have implications for conservation programs that make decisions about when and how often to train animals to recognize predators before their release.