How do bees select and follow routes in cluttered environments?

• Applicant: Dr. Olivier Bertrand
• Subject Area: Sensory and Behavioural Biology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 467027324

Travelling between different locations, sometimes over long distances and through challenging environments, can be vital for many animals. For example, central place foragers, such as ants and bees, travel between food sources and their hive or nest. By integrating the distances and directions along the path travelled during an outbound journey, an insect can estimate the direct way home. However, path integration is subject to noise. A second guidance system based on visual features in the environment may direct insects along previously learnt routes. In the last decade, it became clear that path integration and visual guidance interact in some way in experienced foragers to direct them efficiently between food sources and their home. However, little is known about the processes how foraging insects become experienced. In the proposed project, we want to investigate how bumblebees become efficient foragers in cluttered environments. Earlier studies showed that bees can cross a variety of environments, from open terrains to heavily cluttered environments. We recently observed that they can be trained to follow a route in artificial cluttered terrains. We will build in an elaborate lab setting artificial forests with varying densities, composed of “trees” looking alike or being distinct by their shape, form or colour. We will monitor how bumblebees become experienced in such cluttered environments, from their first encounter with the forest to an almost straight path on their way home. We hypothesise that local punishments, such as the duration of a flight manoeuvre required to avoid a collision with an object on the direct path home or collisions with obstacles trigger the learning of visual cues. We will locally punish bees in various ways and monitor the development of their flights home through clutter as experience increases. The flight paths of naïve bees are convoluted and contain many different motifs, such as arcs, loops, or zigzagging. We hypothesise that this kind of motifs may represent some behavioural building blocks, which, depending e.g. on the environment, are sequenced in a suitable manner constituting a flight trajectory. We will develop analyses to objectively decompose the behaviour of bees into a sequence blocks, compare their occurrences and transition probabilities in various situations, and study their temporal organisation. Our project will help to fill the knowledge gap about how animals become experienced travellers in their often challenging habitats. It will serve to improve our understanding on the building blocks of learning in freely moving animals.

• DFG Programme: Research Grants