Influence of temperature on intraspecific, unbalanced dyadic contests between crabs

Intraspecific agonistic interactions are widespread across the animal kingdom, with many individual morphological and physiological characteristics playing important roles in the fate of disputes. Additionally, changes to environmental conditions can influence the outcomes of animal contests. The shore crab (Carcinus maenas) is a globally distributed species, present in numerous coastal and estuarine temperate systems around the world. Although shore crabs are highly tolerant to changes in temperature, this parameter has important physiological effects on the species' ecology, while its effects on behavior are not fully understood. Our study aims to investigate how different individual characteristics (such as sex, color morphotype, carapace and chela morphology) and temperature conditions affect the dyadic interactions between shore crabs when disputing food resources. In general, the differences in carapace width between opponents, their sexes, color morphotypes and the temperature conditions interacted and were important predictors of the contest fate. We found that the body size and color morphotype of C. maenas determined the fate of dyadic disputes. However, the higher temperatures disrupted the well-established dominance of the larger red color morphotype individuals. Overall, the agonistic contest results suggest higher plasticity than previously acknowledged.