Sex predicts response to novelty and problem-solving in a wild bird with female-biased sexual dimorphism

A wide range of animals, including a number of bird, fish, mammal and reptile species, show sex differences in cognitive tests. Hardly anything is known, however, about whether and how sex-specific non-cognitive factors (e.g. response to novelty) affect the expression of cognition in the wild. We used a series of learning and problem-solving tasks in wild breeding skuas, a species in which females are the larger sex (female-biased sexual size dimorphism). We also evaluated the birds' response to novelty (novel objects) before and after the tasks were administered. Both sexes performed equally well in learning (<i>Discrimination-learning task</i>) and re-learning (<i>Reversal-learning task</i>) food associations with colour and spatial cues, but female skuas outperformed males in problem-solving tasks (<i>String-pulling task</i>, <i>Box-opening task</i>). Females were also less neophobic than males: they were faster at accepting a food reward in novel situations. Better female performance may not imply higher cognition <i>per se</i>. Sex-specific size differences may translate into less or more neophobic behavioural types, which, in turn, predict females' problem-solving success and response to novelty. Species with female-biased sexual dimorphism may present a useful model to assess the interactions between sex, non-cognitive factors and cognition in the wild.