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Title: How insects learn about different goal locations : an analysis of learning and return flights of male and worker bumblebees at the nest and at a feeding site
Author: Robert, Théo Geoffrey
Awarding Body: University of Exeter
Current Institution: University of Exeter
Date of Award: 2017
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Abstract:
Bees and wasps perform learning flights when departing their nest for the first few times or a newly discovered food source. Several studies have described the occurances and structure of these flights in several species, but few have examined how the insects systematically vary the characteristics of their learning flights in various conditions in order to aid the acquisition of visual information. This is best done in a species where individuals and nests can be easily manipulated and tested repeatedly. The aim of this thesis was therefore to investigate learning flights in bumblebees, where we have a good understanding of the structure and variability of flights from previous work and can design controlled experiments. I explored the similarities and differences of learning flights of workers and male bumblebees, observing their departures from the nest or an artificial flower. A second objective was to examine how differences in the learning flights affect the bumblebees’ ability to return the learnt location. The experiments were conducted inside a large greenhouse, under natural light regimes, with two large tables placed far apart, one for simulating the ground from which bees emerged when departing their nest, and the other representing a feeding site with an artificial flower. Female bumblebees performed shorter learning flights when leaving a flower than when leaving their nest, although both locations displayed similar visual scenes. At both locations, the duration and trajectory length of learning flights decreased over successive visits, but the decrease was faster at the flower location than at the nest. Bumblebees fixated both their nest and the flower during their learning flights as well as the landmarks available around the two locations, which suggests that they learned the position of the goal relative to these landmarks. When the nest and the flower were hidden and only three cylinders were shown as landmarks in tests, bees searched as accurately for the nest as for the flower. However, they were more persistent when searching for the nest than for the flower, which was not predicted from the variation of learning flights at the nest and flower locations. Another situation in which bumblebees varied the characteristics of their learning flights, but without an impact on their performance when recalling the learnt information, was after visiting flowers filled with low and high sucrose rewards. The bees performed longer learning flights after drinking at a highly rewarded flower. When departing a poorly rewarded flower, bumblebees did not fixate the flower during their learning flights. Nevertheless, the bees were able to return to both the poorly rewarded flower and the highly rewarded flower equally fast. Given the above findings, it is not evident how different durations or trajectory lengths of bumblebee learning flights might be linked to variations in learning of goal locations. Finally, I show that bumblebees of either sex decide to perform learning flights at locations that are of importance to them. Whilst the female workers always performed learning flights when departing their natal nest, the males did not and simply flew away in a straight line. However, when leaving a flower, the males did perform learning flights with characteristics similar to those of the females’ learning flights. They were also able to return to the flower, showing similar approach trajectories as workers. The thesis discusses these findings in the light of ideas and hypotheses that are linked to differential investment in learning which were observed in the various conditions here. It is also discussed why bumblebees used fixations in different ways when learning about the visual environment surrounding goals that are important to them. Whilst many results are parsimonious with the requirements for learning and active flight control to aid the acquisition of visual information, motivation also seems to play a role in varying the occurances and features of learning flights, such as seen in the bees’ greater persistence to search for their nest than for a flower.
Supervisor: Hempel de Ibarra, Natalie Sponsor: Leverhulme Trust
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.716815  DOI: Not available
Keywords: Bumblebees (Bombus terrestris) ; insects ; navigation ; learning flights ; spatial learning
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