Bumble bees strategically use ground level linear features in navigation

Joanna S Brebner,James C Makinson,Olivia K Bates,Natacha Rossi,Ka S Lim,Thibault Dubois,Tamara Gómez-Moracho,Mathieu Lihoreau,Lars Chittka,Joseph L Woodgate

doi:10.1016/j.anbehav.2021.07.003

Abstract

Extended ground level structures like roads or field edges can be important cues for navigating animals, seen for example in road-following pigeons. In a landscape devoid of skyline cues but with a rectangular grid of pathways and roads, we used harmonic radar to track free-flying bumble bees, Bombus terrestris. Individual bees consistently used ground level linear features for navigation in a wide range of behavioural contexts. Bee exploration flights, search behaviour and foraging routes were shaped by linear features, with bees frequently flying along and parallel to pathways and roads. Comparisons of flight trajectories across these behavioural contexts show that individuals modulated their use of linear features strategically with respect to their individual goals and experience. Bees searching for a feeder used linear features to target their search, while foragers often followed pathways to return to their hive without overshooting. These findings on a major pollinator have important implications for the placements of bee colonies for agriculture and floral resources for conservation.

Highlights

Extended ground level structures like roads or field edges can be important cues for navigating animals, seen for example in road-following pigeons
Our experimental manipulation of hive and feeder location in a landscape with a featureless, flat horizon and a regular grid of ground level linear features demonstrates that bees made extensive use of these features during their exploration, foraging and searching flights
Exploration flights performed by bees in our field site were vastly different to those observed in environments with a variety of skyline and ground level cues (Osborne et al, 2013; Woodgate et al, 2016)

Summary

Introduction

Extended ground level structures like roads or field edges can be important cues for navigating animals, seen for example in road-following pigeons. Pigeons, Columba livia, follow roads (Guilford, Roberts, Biro, & Rezek, 2004; Lipp et al, 2004), bats fly along hedgerows and treelines (Billington, 2003) and turtles follow coastlines (Luschi, Papi, Liew, Chan, & Bonadonna, 1996) Such features may be relevant for pollinators that exploit agricultural terrains which often present sparse visual environments with prominent man-made linear features. We examined how and to what extent bees learn to use linear features during navigation by using a harmonic radar to track free-flying bumble bees, Bombus terrestris, in a unique, visually sparse landscape, characterized by a ground level rectangular grid of roads, pathways and field borders. In the absence of skyline information, any influence of ground level cues can be isolated, allowing us to quantify bumble bees’ use of linear features in exploration flights, searching flights, foraging flights and over route development

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