Mongoose Markets: The Provision and Value of Public Goods

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The trading of goods and services is a fundamental component of human societies, but we are not unique: throughout the animal world, individuals exchange cooperative acts in 'biological markets'. There are lots of examples of non-human animals trading a commodity for itself (e.g., grooming for grooming) or trading one commodity for another (e.g., grooming for help in fights with others). However, our understanding of this market trading has been limited in two main ways. First, by a focus on situations where just one individual receives a benefit (like when someone carries the shopping of a friend). In reality, many cooperative behaviours have multiple beneficiaries (like when someone picks litter in a park). So-called 'public goods' have profoundly different effects on others and so influence relationships between group members in very different ways. The second limitation is a paucity of experiments in natural conditions, which are crucial to avoid measuring odd effects of captive living and to determine exactly how one behaviour influences another (i.e., causality). In this project, we will investigate social factors driving variation in the provision and value of public goods in biological markets. To do so, we will generate new theory from computational modelling and test the predictions using the cross-commodity trading of sentinel behaviour (acting as a raised look-out) and grooming in a tractable wild population of dwarf mongooses.New theory is needed because existing models of biological markets have generally focused on exclusive partnerships in large populations and the trading of single commodities with individual recipients. We will use cutting-edge methods to model the more common scenario where different commodities (including public goods) are exchanged in small family groups where groupmates with non-exclusive friendships repeatedly interact with one another. Dwarf mongooses, Africa's smallest carnivore, are ideal for the testing of our predictions for several reasons. Groups comprise 5-30 individuals who sleep in a burrow, forage and travel together within a shared territory. Throughout the day, all adults act as sentinels - a cooperative act of public good because the individual suspends foraging, adopts a raised position to scan for danger and provides vocal information about danger to all groupmates - and then groupmates groom one another at the burrow before bedtime. Grooming is important both to reduce ectoparasites living in their fur and to maintain social relationships. We have studied these charismatic creatures for over a decade, so have huge amounts of data (from 81 group-years) on sentinel contributions, grooming patterns and the lives of over 200 individuals. Moreover, we have habituated the study population to our close presence, which enables us to collect body-mass data and run experiments (e.g., manipulations of grooming, perceived sentinel contributions and predation risk) in natural conditions.By developing and testing new theory with both long-term data and the results of field experiments, we will determine how (a) the provision of public goods is influenced by receipt of a different commodity and competition among providers, and (b) the value of public goods is affected by their supply and demand. In doing so, we will deepen our understanding of biological markets, group dynamics, cooperation and social evolution, which are topics of interest to a wide range of biologists. Since cooperation and market trading have major interdisciplinary implications, our research will also complement that of anthropologists, psychologists, economists and social scientists. Finally, because helping others is a trait that we admire in family, friends and colleagues, we will use a programme of public engagement activities to enthuse and inform a wider audience about our research on social interactions and the importance of understanding the natural world through blue-skies research.