Abstract
Organisation in eusocial insect colonies emerges from the decisions and actions of its individual members. In turn, these decisions and actions are influenced by the individual's behaviour (or temperament). Although there is variation in the behaviour of individuals within a colony, we know surprisingly little about how (or indeed if) the types of behaviour present in a colony change over time. Here, for the first time, we assessed potential changes in the behavioural type of foragers during colony development. Using an ecologically relevant foraging task, we measured the decision speed and learning ability of bumble bees (Bombus terrestris) at different stages of colony development. We determined whether individuals that forage early in the colony life cycle (the queen and early emerging workers) behaved differently from workers that emerge and forage at the end of colony development. Whilst we found no overall change in the foraging behaviour of workers with colony development, there were strong differences in foraging behaviour between queens and their workers. Queens appeared to forage more cautiously than their workers and were also quicker to learn. These behaviours could allow queens to maximise their nectar collecting efficiency whilst avoiding predation. Because the foundress queen is crucial to the survival and success of a bumble bee colony, more efficient foraging behaviour in queens may have strong adaptive value.
Highlights
Behavioural variation in social insects exists at multiple levels [1], and whilst much is known about variation in behaviour among species [2,3,4], colonies [5,6,7,8,9,10], genetic lines [11,12] and castes [13,14,15], until recently little attention has been paid to the variation in behavioural types among individuals within a colony [16,17,18,19,20]
Two of the three queens performed significantly better than their workers in the learning task (one-way ANOVA, p-value generated in pairwise comparison of Learning Performance Index (LPI) with bootstrapping: colony 1, F (1,22) = 1.903, P = 0.002; colony 4, F (1,17) = 1.947, P = 0.002) indicating that they made fewer errors
While there was no significant difference between the learning ability of the queen and workers in colony 2 (one-way ANOVA, p-value generated in pairwise comparison of LPI with bootstrapping: F (1,16) = 0.873, P = 0.182) the queen notably made fewer errors than 71% of her workers (Figure 3)
Summary
Behavioural variation in social insects exists at multiple levels [1], and whilst much is known about variation in behaviour among species [2,3,4], colonies [5,6,7,8,9,10], genetic lines [11,12] and castes [13,14,15], until recently little attention has been paid to the variation in behavioural types among individuals within a colony [16,17,18,19,20]. Social insect individuals will alter their behaviour, for example their level of aggression, depending on the ecological situation. Some individuals are consistently more aggressive irrespective of the context or situation [21]. This concept forms the basis for behavioural syndromes [21,22] and animal personality [23], whereby individuals exhibit different behavioural types/temperaments. The behavioural types of individuals are important in social insects as the decisions, actions, and fitness of a functioning colony are influenced by the behaviour of its members [10,21,24,25,26]
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