A critical review of research concerning the gut microbiome in dogs and its relationship with behaviour

There is growing interest in how the complex assembly of microorganisms (the microbiome) in an animal’s gut influences various aspects of the host’s health, physiology, and behaviour. However, the microbiome itself is shaped by a range of factors and so the direction of causal effects is difficult to determine. Given growing interest in the interaction between the microbiome and behaviour in dogs, we sought to provide a rapid and accessible introduction to the topic, focused on key concepts and considerations. We start by critically reviewing the scientific literature on the factors affecting the composition of the gut microbiome in dogs. This provides the context for our subsequent assessment of studies that have specifically examined the relationship between the gut microbiome and behavioural traits and related cognitive capabilities in dogs. Emerging evidence suggests a link between gut microbiome composition and behavioural and cognitive outcomes, including anxiety, stress responses, and learning abilities. However, given the relative immaturity of this field, there is little replication and studies are not easily comparable. Accordingly, specific associations and mechanistic explanations need to be treated with caution at this time. Our findings underscore the need for comprehensive, standardised research methodologies, including data sharing, and the need for consistent reporting that clearly recognises and acknowledges the wide range of influential factors (and thus limitations) in proposed control/reference populations. Therefore, claims relating to the influence of the gut-brain axis in dogs need to carefully expressed and nuanced. • Gut microbiome may influence dog behaviour, but specific findings are not definitive. • Preliminary evidence links dogs’ gut microbiota to anxiety, aggression, and cognition. • Standardized methodologies are needed to improve study comparability and replicability. • Future research should adopt robust behavioural measures and longitudinal sampling.