Must marine predators always follow scaling laws? Memory guides the foraging decisions of a pursuit-diving seabird

Abstract

Foraging animals are expected to adapt their movement patterns to their environment in a way that maximizes efficiency. The search strategies they rely on to achieve this is an enduring question in ecology. Scale-free Levy and Brownian search strategies have received particular attention as both strategies are considered effective when prey are abundant and Levy search is thought to optimize success when prey are patchy. Environmental context has been shown to explain Levy and Brownian movement patterns for various marine predators, but potential effects of habitat structure and cognitive skills are often overlooked. We used bird-borne global positioning sensors (GPS) and temperature depth recorders (TDR) to assess flight paths and dive profiles of foraging parental common murres, Uria aalge. Movement patterns while flying and diving were best approximated by Brownian motion even though their primary prey, capelin, Mallotus villosus, are patchily distributed. Contrary to expectations, there was virtually no support for Levy flights. Further analyses revealed that murre foraging activities are not random, but are rather more deterministic. Murres repeatedly returned to previously visited sites (within ∼2 km), indicating a role of memory, and they focused foraging activities using small-scale area restricted search (ARS;