Map and compass navigation: the mechanism and ontogeny of animal maps

Map and compass navigation, a two-step process in which animals use a map to determine goalward directions and a compass to orient in those directions, accounts for a variety of navigational behaviours across animals, from visual landmark navigation in familiar environments, to returning long distances from novel sites. However, while extensive investigation into the sensory basis of maps has implicated roles for visual, olfactory, and magnetic cues, many details of their mechanism and ontogeny are less well understood. Here, we introduce a framework that deconstructs maps into three components: (1) cues, the nature of the environmental properties that animals use to determine goalward directions; (2) structure, the organisation of information used to determine the goalward direction, distinguishing discrete and continuous map structures; and (3) implementation, encompassing strategies relating to how animals approach their goals and how animals combine multiple information sources. In some cases, inherited rules and imprinting are involved in the ontogeny of these components of map and compass navigation. However, in many instances, including those which require extrapolation of gradients or involve flexible navigation between multiple goals, extensive learning is likely required; nonetheless, how animals resolve the spatial arrangement of cues to learn maps, especially over large scales, is little understood. Mechanisms for determining vectors of self-motion, termed path integration, play an important role in map learning in mammals over relatively small spatial scales; we suggest that path integration could play a similar role in map learning in other taxa and over larger spatial scales. This would imply that path integration is more taxonomically widespread and plays a greater role in navigational learning than currently appreciated. This review helps to clarify links between disparate findings and raises questions about navigational mechanisms and ontogeny to better our understanding of map and compass navigation across taxa and scales.