Open Collections

Abstract

Migratory movement is integral to the life histories of many animal species, as they travel in pursuit of essential resources, favourable environmental conditions, and reproductive opportunities. The migrations of marine mammals are among the most impressive, spanning vast expanses of open ocean over months at a time. How they navigate this seemingly featureless landscape remains largely unknown, as are the potential environmental cues that may guide them. Southern elephant seals (Mirounga leonina) provide a compelling model for studying open ocean navigation, as they spend most of their lives at sea and migrate thousands of kilometers to reach small, isolated breeding islands. Using ARGOS satellite locations from 271 southern elephant seals tracked across the Southern Ocean between 2009 and 2019, I quantified the characteristics of their long-distance movements and evaluated them against theoretical predictions that assumed reliance on lunar, solar, and geomagnetic environmental cues. I found that the migratory paths of southern elephant seals were remarkably precise and efficient when returning to breeding islands. Individuals maintained straight-line trajectories that accounted for the curvature of the Earth and corrected for drift caused by ocean currents, despite initiating travel from widely dispersed locations. These findings suggest that southern elephant seals are capable of sophisticated navigation, likely guided by specific environmental cues. My results indicate it is unlikely that lunar and solar cues are used for orientation, but the observed movement patterns closely align with predicted use of geomagnetic cues. Seals consistently followed gradients of geomagnetic inclination, total intensity, and declination, with many paths following a combination of two gradients. Sensitivity analyses suggest that successful navigation would require seals to possess high sensitivity to subtle changes in geomagnetic values, whether following individual cue gradients or using them in tandem. This study is among the first to quantitatively characterize the navigational abilities of southern elephant seals and provides some of the first evidence that pinnipeds may use geomagnetic information for navigation and goal-finding. These findings also highlight the utility of tracking information to investigate animal navigation in species that cannot be studied using traditional experimental approaches, advancing understanding of animal movement and ultimately informing conservation.