Paper Wasp Research

Cognition and Social Life

 

Does an individual need a larger or more complex brain to deal with the dynamic social environment of living in a group? In primates at least, brain volume tends to be correlated with social group size. Primates live in hierarchical societies, where each individual has their own personality and is recognised by other members of the social group. This is necessary to direct appropriate behaviour towards others, depending on the individual’s position in the ‘pecking order’, and to determine how to navigate that established order to maximise individual fitness. Unlike some more derived social insect colonies of ants, bees, and termites Polistes dominula also display individual recognition and strict dominance hierarchies, and behave in specific ways to their superiors/inferiors, and all this in a brain of around 1 cubic millimetre in volume. We are investigating whether this ‘social brain hypothesis’ applies in insect social systems. As well as investigating a correlative relationship between brain size/complexity and social life, we are manipulating the social order in this system by removing dominant individuals and therefore promoting subordinates in the hierarchy. This allows us to investigate whether there is any plasticity in the brains of individuals to adapt to the demands of their new positions, or whether individuals with specific neural architecture have an anatomical advantage from the outset.

Examples of our previous work the Social life of Wasps include Green, Field & Cant 2014 and Field & Cant 2009.

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Aggression and dominance

 

Social hierarchies in animal societies where access to breeding opportunities is not equally shared are generally predicted to display a certain amount of aggressive interaction between dominant and subordinate individuals. Generally this aggression tends to be subtle, low-level signalling behaviour such as posturing displays which, when displayed periodically, serves to reinforce the social order and keep the peace. But how to behave towards conspecifics over time is a question addressed by our research. Theoretically, a subordinate individual should challenge the dominant from time to time in order to test whether their physical state has changed to the point where the challenge would be successful. Experimentally removing a dominant wasp (allowing a subordinate to assume the dominant position) leads to aggressive interactions if the dominant is returned after a time, whereas such interactions rarely occur otherwise. It seems that regular low-level displays serve to maintain the hierarchy, preventing elevated fighting behaviour. The timing of this ‘social memory’ however is still a topic of investigation. When is the right time to reinforce your position or challenge a superior? How long is a social memory?

An example of our recent work on dominance and aggression in Paper Wasps can be seen in Thompson et al 2014.

Strategies for maximising fitness

 

For a social system to evolve through natural selection, there must be some advantage to cooperation over solitary breeding. Why help others rear their offspring at the expense of your own opportunities for direct reproduction? By helping relatives to rear offspring, individuals increase the chances that whatever genes they share with those relatives are passed on to future generations. Additionally, if a solitary wasp dies prior to the emergence of her offspring, then those offspring will also die, whereas if a member of a cooperative group dies, there are still others which can sustain the offspring to adulthood, an insurance policy so to speak.

Examples of our research into the strategies that wasps use to maximise their fitness include Donaldson et al 2014 and Shreeves et al 2003

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Wasp Brain Animation

 

Animated video using data obtained using Micro Computed Tomography of the digger wasp Ammophila pubescens.