David Diez Méndez

The world is changing at a rapid pace, and animals need to adapt to these changes to persevere. Animal personality describes that individuals show consistency in the differences in their responses to environmental variation across time or context. However, optimizing behavioural traits in a changing environment requires a certain degree of plasticity. Environmental responsiveness, i.e., behavioural plasticity, stands out as a key feature to adjust an individual's behaviour to a variable environment. Behavioural plasticity is often seen as a complementary aspect of animal personality, since individuals might consistently differ in their plasticity. The underlying mechanisms linking changing environments to plasticity in behavioural traits are largely unknown. We propose that the gut microbiome (GM), often considered the "second genome" of an organism, provides the bridge between environment and host behaviour. Gut bacteria that produce specific metabolic compounds such as neurotransmitters or their precursors, may be essential components explaining behavioural consistency and plasticity. Since diet is a major determinant of GM community composition, we hypothesize that changes in the environment impact diet and lead to changes in GM functionality that ultimately affect animal personality. NEUROGUT will explore the functionality of GM as a mechanism linking the changing environment and animal personality during the first year of a wild bird species by conducting parallel diet experiments in the wild and in aviaries.