The serotonin transporter gene could play a role in anti-predator behaviour in a forest passerine

Elucidating associations between behavioural variation and genes may help to understand the co-existence of different behavioural phenotypes in natural populations. In birds, two main candidate genes are known to affect exploratory and risk-taking behaviour through the neurotransmitter system: the dopamine receptor D4 gene (DRD4) and the serotonin transporter gene (SERT/SLC6A4). In a small passerine bird, the great tit (Parus major), anti-predator responses (hissing or non-hissing behavioural type) towards a nest predator differ consistently between individuals. As defensive anti-predator behaviours are likely related to variations in neurotransmitter systems, we tested the associations between polymorphisms of the two candidate genes (SERT and DRD4) and the propensity to give hissing calls towards a nest predator in incubating female great tits. We found that acoustic anti-predator responses in wild birds were linked to a single-nucleotide polymorphism in the SERT gene (SNP187 in exon 1), but not in the DRD4 gene. The polymorphism in the SERT gene explains about 16% of the total variance in hissing behaviour. However, as the sample size in this study is quite small, these results are preliminary and should be replicated in future studies.