The geomagnetic field does not appear to influence navigation in Eastern painted turtles

Abstract

AbstractGeomagnetic cues provide important information to guide aspects of migration, from the general direction of movement to informing an animal's specific location on the planet. Although such cues are used by many long‐distant migrants, its use for short‐ and moderate‐distance migrations is less clear. We have been studying overland migratory movements in a population of Eastern painted turtles where animals use one of four precise, highly predictable routes to locate water sources during migration. Our previous work suggests a strong role of learning and spatial memory in this precise navigation, but the cues used and the context for their use are unknown. Here, we present a series of controlled field experiments in which we test the hypothesis that geomagnetic cues are utilized when Chrysemys picta engage in these intricate, overland movements. We fitted turtles with 3,309 Gauss magnets (n = 10) or aluminum disk controls (n = 5) and surveyed their ability to locate and navigate their routes during migration; turtles were similarly tested for these abilities outside of the context of migration (magnets, n = 30; control, n = 30). Strong magnets (3,309 Gauss) on their carapaces did not disrupt turtles’ ability to locate the paths or the precision with which they navigated them. Turtles, irrespective of treatment, found their paths and/or navigated their paths with the same high precision that we observed in controls and our previous work, both within and outside of the context of migration. Thus, alternative types of cues must be in use that explain the high precision and high reliability of path location over time. Future studies should examine alternative cues used in migratory navigation and the creation of complex and specific paths.