Innovative behaviors such as exploiting novel food sources can grant significant fitness
benefits for animals, yet little is known about the mechanisms driving such phenomena,
and the role of physiology is virtually unexplored in wild species. Two hypotheses
predict opposing effects of physiological state on innovation success. On one hand,
poor physiological condition may promote innovations by forcing individuals with poor
competitive abilities to invent alternative solutions. On the other hand, superior
physiological condition may ensure greater cognitive capacity and thereby better problem-solving
and learning performance. To test these hypotheses, we studied the behavior of wild-caught
house sparrows (Passer domesticus) in 4 novel tasks of food acquisition, one of which
was presented
to the birds in repeated trials, and we investigated the relationships of individual
performance with relevant physiological traits. We found that problem-solving performance
across the 4 tasks was moderately consistent within individuals. Birds with lower
integrated levels of corticosterone, the main avian stress hormone, solved the most
difficult task faster and were more efficient learners in
the repeated task than birds with higher corticosterone levels. Birds with higher
concentration of total glutathione, a key antioxidant, solved 2 relatively easy tasks
faster, whereas birds with fewer coccidian parasites tended to solve the difficult
task more quickly. Our results, thus, indicate that aspects of physiological state
influence problem-solving performance in a context-dependent manner, and these effects
on problem-solving capacity, probably including cognitive abilities, are more likely
to drive individual innovation success than necessity due to poor condition.
