Effects of nutritional manipulation on intranidal social behaviour in a small carpenter bee

Abstract

Understanding how subordinate altruistic roles arise among genetically similar individuals is critical to understanding the evolution of animal societies. In particular, maternal manipulation of offspring resources is an understudied process by which mothers may produce cooperative phenotypes among offspring. Mothers of the small carpenter bee Ceratina calcarata frequently produce a smaller underprovisioned daughter, known as the dwarf eldest daughter (DED) in the first cell of their nests. This DED is more subordinate and more easily coerced into helping siblings, aiding mothers in guarding and supplemental foraging and feeding of adult siblings. Colonies of these bees thus offer a unique opportunity to study the indirect effect of nutritional manipulation on behaviour, in particular mutual tolerance. We hypothesized that aggression would be greatest in the presence of DEDs, as they are actively coerced by their mothers to forage and feed their siblings. Here we experimentally added nutrition to the first cells of C. calcarata observation nests to test the effect of nutritional manipulation on colony intranidal behaviour. Using infrared cameras, control ( N = 13) and nutritionally supplemented nests ( N = 13) were observed for a total of 607.5 h. Behaviours were scored and categorized. Although aggression was unaffected, avoidant behaviour was greater in nutritionally supplemented nests. This study is the first experiment examining the effect of nutritional manipulation on intranidal behaviour in a stem nesting bee. Our results indicate that maternal manipulation and nutritional deprivation by mothers is critical to the production of mutual tolerance and division of labour. • We test effects of nutritional manipulation on mutual tolerance in C. calcarata. • Maternal manipulation of offspring nutrition influenced colony behaviour. • Avoidance behaviour increased in colonies with nutritional supplementation. • Control colonies with naturally underprovisioned daughters were more tolerant. • Mutual tolerance is among the most rudimentary social requirements.