Effects of sibling competition and physiological and behavioural differences on problem-solving of wild cavies (Cavia aperea).

Behavioural innovations can be crucial for animals to adjust to changing environments and to exploit novel resources. While ecological and evolutionary implications of innovativeness have been investigated intensely, the proximate mechanisms underlying this behaviour are less well understood. Intrinsic individual differences arising from differences in competitive abilities have been hypothesised to drive differences in innovation propensity (bad-competitor hypothesis). We here investigated the relationship between early-life competition among siblings as well as effects of several physiological and personality traits on innovation propensity in young wild cavies (Cavia aperea). Our study aimed to test whether competitive situations in early life, such as being a small sibling or being born in larger litters, enhanced innovation propensity. Furthermore, we tested if intrinsic physiological or behavioural characteristics differed between solvers and non-solvers. We found that neither size rank nor litter size influenced innovation propensity in young cavies at independence. Likewise, physiological traits such as cortisol level, heart rate, and resting metabolic rate did not differ systematically between solvers and non-solvers, although heart rate and resting metabolic rate were repeatable. However, individuals that interacted more with novel objects and innovation tasks were more likely to solve them. Our results suggest that innovation propensity is not shaped by early-life competition or physiological differences but may rather develop consistent individual differences later in life, potentially by competition for mating opportunities.