Learning capabilities enhanced in harsh environments: a common garden approach

Abstract

Previous studies have suggested that the ability to inhabit harsh environments may be linked to advanced learning traits. However, it is not clear if individuals express such traits as a consequence of experiencing challenging environments or if these traits are inherited. To assess the influence of differential selection pressures on variation in aspects of cognition, we used a common garden approach to examine the response to novelty and problem-solving abilities of two populations of black-capped chickadees (Poecile atricapillus). These populations originated from the latitudinal extremes of the species's range, where we had previously demonstrated significant differences in memory and brain morphology in a multi-population study. We found that birds from the harsh northern population, where selection for cognitive abilities is expected to be high, significantly outperformed conspecifics from the mild southern population. Our results imply differences in cognitive abilities that may be inherited, as individuals from both populations were raised in and had experienced identical environmental conditions from 10 days of age. Although our data suggest an effect independent of experience, we cannot rule out maternal effects or experiences within the nest prior to day 10 with our design. Nevertheless, our results support the idea that environmental severity may be an important factor in shaping certain aspects of cognition.

Figure 1.

Latency to the completion of a problem-solving task (removing a weighted, transparent cover from a well containing a wax worm) in black-capped chickadees. Pre- and post-treatment exposure of a wax worm on the testing apparatus controlled for motivation, the tendency to feed on the floor of the cage and habituation to the testing set-up. Filled circles, Kansas; open circles, Alaska.

Figure 2.

The response to novelty of black-capped chickadees as assessed by the latency to (a) approach, (b) sit on and (c) take a wax worm from a novel feeder. Pre- and post-treatment exposure of a wax worm in a familiar feeder controlled for motivation and the tendency to feed on the floor of the cage. Filled circles, Kansas; open circles, Alaska.