Causes and consequences of individual forager variability in social bees

Thesis by publication.Cotutule thesis with Université Paul Sabatier (Toulouse, France).Includes bibliographical references.General introduction -- 1. Why bees are so vulnerable to environmental stressors -- 2. The properties of pollen and nectar collection in a honey bee colony -- 3. The majority of honey bee (Apis mellifera) colony productivity is supplied by a minority of foragers -- 4. Inter-individual variability in the lifelong foraging activity of bumblebees -- 5. Inter-individual variability in the foraging behaviour of traplining bumblebees -- 6. Sublethal effects of miticides on honey bee visual learning -- General discussion -- Appendices.In social insects, such as bees, different individuals specialise in the collection of different resources, and it is assumed that natural behavioural variability among foragers contributes to a self-organised optimisation of colony performance. Currently, bee populations are facing an increasing number of environmental stressors, known to disturb the behaviour of individuals, presumably upon their impact on cognitive capacities. Hence it is important to learn more about how stressors impact on individual foraging behaviour to understand how a colony maintains effective nutrition and development. In this thesis in cognitive ecology, I examined the different foraging strategies for the different macronutrient sources, pollen and nectar, and the inter-individual variation in bee foraging performance. I also looked at how stressors, such as pesticides, can impact on bee foraging efficiency. I compared two social Hymenoptera that vary in their level of social complexity: the European honey bee (Apis mellifera L.) and the buffed-tailed bumblebee (Bombus terrestris L.). I used Radio Frequency Identification (RFID) to automatically track the foraging behaviour of bees throughout their life. I found that honey bee and bumblebee colonies rely on a subset of very active bees to supply the whole colony needs. In honey bees, these foragers are more efficient and collect more pollen. I also identified different strategies for pollen or nectar collection in both species. Using manipulative experiments, I then showed that bees exhibit consistent interindividual different behaviours in a spatial learning task and that pesticides impair visual learning. My thesis aims at better explaining the causes of vulnerability of pollinators to sublethal pesticides and other environmental stressors. The results highlight the need for considering behavioural diversity as an adaptation for social insects, as well as a potential dimension of colony-level vulnerability to environmental stressors that can impair the whole colony nutritional balance.1 online resource (204 pages