An empirical test of the role of learning in translocation

Abstract

Translocation centers on the introducing, reintroducing, or augmenting populations by moving individuals from existing wild source populations to different locations with purportedly suitable habitat. Despite much research in and application of translocation, this technique is often marred by low success rates. While many possible factors could contribute to low translocation success, outcomes are often improved when researchers engage in a soft release, which provides the animals with the opportunity for extra time to acclimate to their release site, indicating that aspects of learning may play an important role in translocation success. To test the importance of the time available for learning in translocation success, we performed hard and soft releases into an existing population of Eastern painted turtles Chrysemys picta that has experienced seasonal ephemeral water sources and in which resident turtles navigate to new permanent sources of water with extreme precision (±3.5 m) using specific routes known to be facilitated by learning. Translocated adult turtles in both hard- and soft-release groups failed to successfully negotiate upland habitat, even when given 3 months to prospect and learn (the maximum time possible in our system). Likewise, turtles in both groups moved more slowly, stopped more frequently, and were slower to restart movement than resident adults. Finally, both translocated groups exhibited significant drops in body mass and elevated rates of predation. In contrast, juveniles from the same donor population navigated to alternative water successfully, with movements and mortality rates not different from resident animals. These results indicate that complex aspects of cognition beyond time to learn can influence translocation success and highlight the importance of considering how and when animals learn.