Data set for: Dominance is associated with reduced cleaning activity in group-living Elacatinus prochilos gobies

<em>Elacatinus prochilos </em>can be found in two socio-ecological contexts: inhabiting cleaning stations, where they live in pairs and feed by removing ectoparasites from larger marine organisms (cleaners), or barrel sponges, where they live in dominance-hierarchies and rarely engage in cleaning interactions (sponge-dwellers). To better understand which factors influence cleaning activity in facultative species, we used individuals from a controlled social structure (small groups with dominance hierarchy) and feeding conditions (better access to food to dominants). We found that dominance significantly decreased cleaning activity in sponge-dwellers but not in cleaners. Our study highlights the importance of testing the flexibility of individuals in different social contexts to better understand the evolutionary importance of adaptive behavioral flexibility.