Horse owners know that some mounts are more spirited than others, and dog owners readily speak of their companion’s temperament. But can one speak of character or personality in the same way as in psychology for human beings?

An original answer to this question has recently been provided by researchers working with bees. Yes, it appears that these insects have different personalities. Let us take an example. One often observes a bee leaving the hive, exploring the surroundings, then returning after having found new flowers and informing its nestmates by means of a “dance”. Other workers then move in the indicated direction. All this has been known since the description of these behaviours by Karl von Frisch in 1944. And yet? By marking bees with small spots of paint, researchers showed that some of them (between 5 and 25 percent of foraging bees) systematically search for new food sources (even when flowering fields have already been discovered), whereas others merely follow the indications provided by the dance. Are these exploratory bees specialised in food searching, or does this reflect a broader difference, a temperament of certain individuals particularly attracted to novelty?

Homebound or exploratory bees?

To find out, Zhengzheng Liang and his colleagues at the University of Illinois focused on a rarer behaviour: the search for a new nesting site. When part of the bees in a hive forms a swarm to found a new colony, it is again a small number of individuals that set out in search of a favourable location (a cavity in a tree trunk, a man-made hive). When such a site is discovered, the exploratory bees return to the swarm and indicate it to the others by dancing. These are the same individuals that also tend to search for food more readily. This thus appears to be a kind of “personality trait” expressed in two different contexts: some individuals seek novelty and venture out, while others prefer safety and remain in already known areas or at least those identified by the exploratory bees.

Can one truly speak of personality differences in these bees? This is how the study has sometimes been presented, although the researchers themselves do not use this term in the original article. Nevertheless, the scientific community now accepts that one can speak of personality in animals when consistent individual differences are observed over time and expressed across different contexts. The behaviour of bees clearly meets this definition.

But what underlies these behavioural differences? Z. Liang and his colleagues investigated possible genetic bases. After providing captive bees with only a single food source for several days, they added a new one that differed in both location and odour. Some foragers then turned to this new source, while others preferred to keep the original one. This procedure was repeated several times over several days to minimise the probability of accidental discovery: bees that had discovered at least two new food sources were considered exploratory, whereas those that had never left the first source were considered homebound.

The expression of certain genes in the bees’ brains proved to differ depending on whether the bees were exploratory or homebound. These genes are linked to signal transmission via neurotransmitters such as dopamine, glutamate, GABA, or octopamine (the latter substance, like dopamine, is a catecholamine and acts as a neurotransmitter in invertebrates). Some of these genes are similar to those that, in vertebrates, are involved in regulating novelty seeking and the reward system. Thus, in humans, a gene encoding a dopamine receptor is also associated with novelty seeking. A curious human and a curious bee would therefore share such genes—of course, with certain differences.

Does gene expression influence the behaviour of bees, or does the adventurous behaviour of some individuals stimulate the expression of these genes? To find out, homebound bees were fed syrup supplemented with glutamate or octopamine and became more exploratory. Conversely, adding a molecule that blocks the action of glutamate promoted homebound behaviour. These effects affect only exploratory behaviour, not the general tendency to move or to forage. It is therefore indeed genetic differences that influence bee behaviour.

However, the mechanisms involved remain unclear, especially since these effects do not appear systematically: food availability, the state of the hive, and the genotype of the foragers likely also influence exploratory behaviour. Moreover, adding GABA has no effect, and some contradictory effects have been observed. Further studies are therefore required, but this work already reveals striking similarities between certain factors influencing human personality and that of the bee! (Article published in Cerveau & Psycho No. 52, July 2012)

 

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See also: 

► The individual intelligence of the bee

► Behaviour and cognition: what a mini-brain can teach us

► Are bees victims of their intelligence?

► The intelligence of bees

► The bee can perform additions and subtractions

► Visual recognition in insects

► The bees’ geometric sense