Examining the fitness benefits of social plasticity to prey availability in bottlenose dolphins

A key explanation for phenotypic plasticity is that changing behaviour to match conditions increases fitness. Affiliative social associations with conspecifics can be important for coping with challenging conditions, and therefore plasticity in social behaviour in response to environment variation may bring fitness benefits. Here we test the adaptive benefit of social plasticity by quantifying female bottlenose dolphins' (Tursiops truncatus) plastic responses to salmon (Salmo salar) abundance and determine if either this plasticity or mean social behaviour is associated with calving success. We found that more gregarious females and those better connected to all parts of the entire social network had higher calving success, but plasticity in social behaviour in response to salmon abundance was not associated with this component of fitness. This lack of relationship may have arisen as salmon abundance in either current or previous years was not associated with the probability of producing a calf. We therefore demonstrate that being more social is positively associated with females' calving success in our study population, but social plasticity itself is not associated with fitness benefits, questioning whether this is likely to be a mechanism for this population of dolphins to cope with challenging environmental conditions.