Superb Fairy-wren Malurus cyaneus
It has been shown in many animal species that individuals behave consistently differently from each other, a phenomenon better known as animal personality. We use a natural population of cooperatively breeding superb fairy-wrens to study the effects of personality on demography and individual life-histories in a complex social system. We have performed captive personality tests on a great number of individuals in our population. In this study firstly we showed that different behaviours are correlated to form a continuum from reactive to proactive personality types. Secondly we showed that these behaviours are repeatable over the long term. Finally, adult behaviour was related to stress response at the nestling stage, indicating that individual personalities are stable throughout individuals’ lives.
The pace-of-life syndrome (POLS) hypothesis states that individuals with proactive personalities ‘live fast and die young’. In other words, individuals are expected to trade off future and current reproduction depending on their personality. The more risky behaviour of proactive individuals indicates their prioritisation of current over future reproduction. This should reduce their short-term survival prospects compared to the more risk-averse reactive individuals (i.e. fast versus slow pace of life). We showed that, in accordance with this hypothesis, more proactive individuals are less likely to be present in the population a year after the personality test. Disappearance is a good indication of mortality among female breeders and males (the philopatric and helping sex), as they generally disperse only very short distances, if at all. It is more difficult to distinguish survival from dispersal in juvenile females, as they typically disperse out of the population. We showed the same pattern of lower presence of more proactive individuals a year after the test when juvenile females were excluded. This indicates that short-term survival is indeed related to personality type in superb fairy-wrens and that this POLS applies to at least both males and female breeders.
This is one of the first studies in the wild showing long-term stability of personality types as well as associated paces of life. The result warrants follow up studies at a finer scale to find out at which stages in individual life-histories personality plays a crucial role.
Much of the work described above was conducted as part of Michelle Halls postdoctoral research. She is studying the individual differences in the behaviour of superb fairy-wrens. Michelle is currently situated at the School of BioSciences at the University of Melbourne. More information about Michelle can be found on the People page.
Photo: Ashton Dickerson