The behavioural patterns observed in many organisms generally result from the integration of both external and internal cues. Why do animals behave the way they do? The study of the proximate and ultimate mechanisms underlying animal behaviour tries to answer this question. Although various approaches have been developed for examiningoften quantitatively and with increasing specificity and resolutionthe roles genes play in the regulation of behaviour, until recently they were limited to

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... al candidate genes and often neglected ultimate mechanisms. Advances in genomic approaches in recent years have made it possible to examine gene expression patterns (in the brain and elsewhere) on a genomic scale even in nontraditional, yet ecologically and evolutionarily important model systems. As behavioural genomics begins to integrate proximate and ultimate mechanisms of animal behaviour, we may finally understand why animals behave the way they do.