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The evolutionary ecology of cognition across a heterogeneous landscape

Final Report Summary - EVOLECOCOG (The evolutionary ecology of cognition across a heterogeneous landscape)

The aim of EVOLECOCOG was to examine some of the underlying causes of individual variation in animal cognition and animal personality, and to explore what these meant for the lives of birds. To do this we developed a new automated system that measured discrimination learning (and reversal discrimination learning) in free-living birds (great tits and blue tits). In addition, we developed and validated a new task in the wild for measuring inhibitory control, a cognitive trait commonly studied in human studies of impulsive disorders, but scarcely within animal populations. And in captivity, we adapted a simple problem-solving task that allowed three different kinds of solutions that limit the effects of motor bias. These different measures were then investigated in a variety of new ways.

Our discrimination learning data allowed us to demonstrate that, in the “producer-scrounger foraging game”, learning is important when producing and scrounging, that individual learning in both covary negatively, and that this primarily occurs because of individual plasticity, though the covariation partly arose at the between individual level in the blue tit. This means that selection is likely to occur on these two traits independently of one another, even though they covary. Furthermore, manipulating who birds fed with (familiar, unfamiliar) during the learning process led to a persistent change in sociality metrics, and this led to a difference in cognitive performance.

Another focus of the project was to examine the role of the gut microbiome, or enterobiome, in driving cognition and fitness, which has scarcely been examined outside the field of human biology. Experimental manipulation of the diet in captivity led to parallel changes in the enterobiome and problem-solving performance, which themselves were correlated. In the wild, the enterobiome in eight day old nestlings predicted weight a week later and their survival to fledgling, a rare demonstration of such a fitness effect. Further analyses demonstrated a link between the enterobiome and stress, as measured by the hormone Corticosterone, and that these factors were associated with problem solving or personality, but not both, pointing to complex causes of variation in these behavioural traits. Staying with innovative problem solving, in another study using personality selection lines, we show little influence of personality on problem solving performance. Instead consistent differences between individuals in serial problem-solving performance were explained entirely by motivation, by selective attention, and by experience, the latter being the only example of positive feedback explaining such variation.

Considerable focus was put on inhibitory control. We showed that it explained individual foraging plasticity independently of similar effects of personality on plasticity when faced with the choice of continuing to feed on familiar or a new food source. Inhibitory control measured at the nest related to how often birds fed their young, and to diet measured using DNA metabarcoding of faeces. Problem solving also predicted diet during the winter. Together these data provide novel insight into how individual variation in one of the most fundamental but difficult to measure behaviours in many animal species, diet, is linked to these intrinsic sources of behavioural variation, supporting the hypothesis that they reflect alternative foraging strategies.

We also used an experimental approach to show that differences among individuals in how efficiently they built nests were consistent, and therefore likely adaptive rather than being innate. And against expectations, nest building performance decreased with age, even though hatching success was higher among better built nests. Finally, we used playbacks of song to show that although enemy recognition in the ‘dear neighbour effect’ may be beneficial, it also seems to have a fitness cost.

EVOLECOCOG has shed new light into how individual variation in a range of cognitive traits arises and how it affects behaviour.