Lost: on what level should we aim to understand animal navigation?

Abstract

Given that all interactions between an animal and its environment are mediated by movement, questions of how animals inherit, refine and execute trajectories through space are fundamental to our understanding of biology. As with any behavioural trait, navigation can be thought of on many conceptual levels – from the mechanistic to the functional, and from the static to the dynamic – as laid out by Niko Tinbergen in his four questions of animal behaviour. Here, we use a navigation-centric interpretation of Tinbergen's questions to summarise and critique advances in the field of animal navigation. We discuss the ‘state of the art’; consider how a proximal/mechanistic understanding of navigation is not a prerequisite to understanding ultimate questions of evolutionary/adaptive importance; propose that certain aspects of animal navigation research – and certain taxa – are being neglected; and suggest that extreme experimental manipulations might lead to the mischaracterisation of non-adaptive ‘spandrels’ as functional navigational mechanisms. More generally, we highlight pressing questions within the field, the answers to which we believe are within reach, and highlight the important role that novel methods will have in helping us elucidate them.

Gauge-and-compass migration: inherited magnetic headings and signposts can adapt to changing geomagnetic landscapes

“…For actual migration systems, this has only been assessed for migration based on correlated random walks—per definition less directed than compass courses—with supplemental navigational abilities based on geomagnetic information [ 38 ]. While gradient-based navigation using innate or early-learned information offers the possibility to correct for imprecision or displacement [ 88 ], e.g., by currents, it could also produce inefficient migrations when gradients in field components are closely aligned [ 9 , 29 , 38 , 90 ]. Our results suggest that constant-heading migration modulated by magnetic signposts could be sufficiently robust to variable and changing geomagnetic fields, at least given suitable compass precision and intrinsic variability in inherited headings.…”

“…While global patterns of avian migration can be explained as efficient energy acquisition of seasonal resources [ 91 ], enabling hindcasts of prehistoric migration routes [ 22 , 77 ], little is understood regarding the population consequences of how migratory orientation is transmitted across generations [ 43 , 88 , 89 ]. Using an evolutionary algorithm approach enables population-level assessments of how inherited migratory orientation programs can both mediate and constrain adaptation of historic and novel migration routes.…”