Experimental evidence for adaptive personalities in a wild passerine bird

Abstract

Individuals of the same species differ consistently in risky actions. Such 'animal personality' variation is intriguing because behavioural flexibility is often assumed to be the norm. Recent theory predicts that between-individual differences in propensity to take risks should evolve if individuals differ in future fitness expectations: individuals with high long-term fitness expectations (i.e. that have much to lose) should behave consistently more cautious than individuals with lower expectations. Consequently, any manipulation of future fitness expectations should result in within-individual changes in risky behaviour in the direction predicted by this adaptive theory. We tested this prediction and confirmed experimentally that individuals indeed adjust their 'exploration behaviour', a proxy for risk-taking behaviour, to their future fitness expectations. We show for wild great tits (Parus major) that individuals with experimentally decreased survival probability become faster explorers (i.e. increase risk-taking behaviour) compared to individuals with increased survival probability. We also show, using quantitative genetics approaches, that non-genetic effects (i.e. permanent environment effects) underpin adaptive personality variation in this species. This study thereby confirms a key prediction of adaptive personality theory based on lifehistory trade-offs, and implies that selection may indeed favour the evolution of personalities in situations where individuals differ in future fitness expectations.

Evidence of social niche construction: persistent and repeated social interactions generate stronger personalities in a social spider

“…Our data suggest that, at least in this species, four weeks of repeated social interactions are needed to fully establish social niches. While several studies have now investigated how different ecological factors influence among-individual variation in behaviour [4][5][6]11], fewer have investigated how these factors generate individual consistency in behaviour (but see [19,34]). Our study demonstrates that the stability of the social environment may be especially influential in generating and even reinforcing individual differences once they appear.…”

“…While there are now a number of welldeveloped theoretical models predicting potential causal mechanisms (reviewed in [1][2][3]), thus far empirical tests of these predictions are extraordinarily few (but see [4][5][6]). In order to fully explain the presence of consistent individual differences in behaviour, or personalities, a potential mechanism would need to address the two key aspects of personality: among-individual variation in behaviour and within-individual consistency over time.…”

Characterizing behavioural ‘characters’: an evolutionary framework

“…A taxidermic mount of a male great tit was presented as a visual stimulus with a playback song as an acoustic stimulus (detailed below). In each year, each male was subjected to four aggression tests during its first breeding attempt (defined as attempts initiated within 30 days after the first egg of the year in all of the plots was found; [21]). Each male was subjected to two simulated territorial intrusions during egg-laying (1 and 3 days after its first egg was observed) and two during incubation (1 and 3 days after clutch incubation was confirmed).…”

Senescence rates and late adulthood reproductive success are strongly influenced by personality in a long-lived seabird

“…This was carried out by fitting the models below, using a loop which varied the boldness scores input per iteration of the model. For every parameter in the model, we present the 95% CIs for every model parameter, based on the 1000 iterations [35]. We present the full tables of results in the electronic supplementary material, appendix S4, with all parameter estimates on the link scale.…”