Friendship across species borders: factors that facilitate and constrain heterospecific sociality

Flocks of starlings, herds of wildebeest, schools of fish, swarms of locusts, colonies of ants, bees and wasps – these examples of sociality are among the most intriguing phenomena in the natural world. It is not surprising, therefore, that the question of why organisms live in groups has attracted a lot of research attention, and today, we have fairly nuanced and in-depth answers to this question. However, our current understanding of sociality comes almost entirely from an intraspecific context, i.e. based on groups of individuals of the same species. We know comparatively little about heterospecific sociality, i.e. social groups or associations among individuals of multiple species.

In a recent paper in the Philosophical Transactions of the Royal Society of London B, Hari Sridhar and Vishwesha Guttal from the Centre for Ecological Sciences, survey and synthesise documented examples of heterospecific sociality in the wild, and propose a conceptual framework to understand how organisms decide whether to group with individuals of their own species (conspecifics) or of a different species (heterospecifics). The authors argue that social partner choice is best viewed as a continuum: some social benefits can only be obtained from conspecifics, some can only be obtained from heterospecifics, and some can be obtained both from conspecifics or heterospecifics.  In cases where both are possible, Sridhar and Guttal propose that factors such as relevance of partner, quality of benefit provided, cost of competition and cost of activity matching will determine whether conspecifics or heterospecifics are chosen.

Paper citation: Hari Sridhar and Vishwesha Guttal, 2018, Friendship across species borders: factors that facilitate and constrain heterospecific sociality, Phil. Trans. Royal Society of London B, 373: 20170014.

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