Effect of social defeat in a territorial bird (Parus major) selected for different coping styles.

We addressed the questions (i) whether a social defeat triggers similar autonomic and behavioral responses in birds as is known from mammals and (ii) whether individuals that differ in coping style differ in their reaction to a social defeat. Adult captive male great tits (Parus major) from either of two different selection lines for coping style were used to test the effect of social defeat by an aggressive resident male conspecific on subsequent social and nonsocial behaviour, body temperature, breath rate and body mass. These parameters were measured 1 day before (baseline), immediately after and at Days 1 to 3 and 6 after the social interaction took place (Day 0). Social defeat decreased social exploration and increased body temperature substantially for at least 1 day in all birds. Breath rate and body mass were not affected. Birds belonging to the more aggressive and bolder line showed impairment in activity immediately after the social defeat. This is to our knowledge the first report showing that psychosocial stress in birds can have a similar impact as in rodents, but with a shorter recovery time. This might be due to species-specific differences in sensitivity to social stress, or to differences in the way social stress was induced.

Additive and nonadditive genetic variation in avian personality traits.

Individuals of all vertebrate species differ consistently in their reactions to mildly stressful challenges. These typical reactions, described as personalities or coping strategies, have a clear genetic basis, but the structure of their inheritance in natural populations is almost unknown. We carried out a quantitative genetic analysis of two personality traits (exploration and boldness) and the combination of these two traits (early exploratory behaviour). This study was carried out on the lines resulting from a two-directional artificial selection experiment on early exploratory behaviour (EEB) of great tits (Parus major) originating from a wild population. In analyses using the original lines, reciprocal F(1) and reciprocal first backcross generations, additive, dominance, maternal effects ands sex-dependent expression of exploration, boldness and EEB were estimated. Both additive and dominant genetic effects were important determinants of phenotypic variation in exploratory behaviour and boldness. However, no sex-dependent expression was observed in either of these personality traits. These results are discussed with respect to the maintenance of genetic variation in personality traits, and the expected genetic structure of other behavioural and life history traits in general.