Abstract
The Biological Market Theory (BMT) posits that cooperation between non-human animals can be seen as a mutually beneficial exchange of commodities similarly to what observed in human economic markets. Positive social interactions are commodities in non-human animals, and mutual exchanges fulfilling the criteria of the BMT have been shown in several species. However, the study of biological markets suffers from methodological limitations that are mainly linked to the difficulty of clearly identifying the currencies and their exchanges in the short-term. Here, we test whether bonobo females are more attractive during their maximum swelling phase, whether they exchange grooming and Genito-Genital Rubbing (GGR) on a daily level of analysis, and whether these daily exchanges fulfil the BMT criteria. Females engaged more in GGR when their sexual swelling was in the maximum phase. Moreover, they exchanged grooming and sex according to the daily “market fluctuations” associated with swelling status. Females in the minimum phase (low-value) increased their probability to engage in GGR with females in the maximum phase (high-value) by grooming them preferentially. In line with the supply/demand law, the female grooming strategy varied depending on the daily number of swollen females present: the higher the number of swollen females, the lower the individual grooming preference. As a whole, our study confirms BMT as a valid model to explain daily commodity exchanges as a function of the temporary value of traders, and underlines the importance of a day-by-day approach to unveil the presence of a biological market when the value of traders frequently changes.
Highlights
The Biological Market Theory (BMT) posits that cooperation between non-human animals can be seen as a mutually beneficial exchange of commodities to what is observed in human economic markets[1]
Females engaged significantly less in Genito-Genital Rubbing (GGR) when they were both in the minimum swelling phase, compared to when at least one female of the dyad was in the maximum swelling phase (Randomization paired t9 = − 2.275, P = 0.027) (Prediction 1 supported)
Our results confirm the key role of sexual swelling in bonobos and provide new insights on the exchange of grooming with sex on a daily basis
Summary
The Biological Market Theory (BMT) posits that cooperation between non-human animals can be seen as a mutually beneficial exchange of commodities (i.e. goods or services) to what is observed in human economic markets[1]. We focus on the bonobo (Pan paniscus) to fill this gap by exploring the possible existence of a biological market regulating the exchanges of social interactions in females living in two stable social groups To reach this goal, we focussed our analyses on the daily fluctuation of grooming and socio-sexual interactions as a function of the swelling status of actor and receiver. As far as we know, it has never been demonstrated that the Biological Market Theory explains the exchange of commodities in bonobos, it has been h ypothesized[20]
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