Integrating behaviour, physiology and survival to explore the outcome of reintroductions: a case study of grey partridge

Abstract

Personalities, i.e. consistent individual differences in behaviour, have been found in many animal populations. However, the reasons why personalities emerge, how they persist and the consequences they have in a changing environment are poorly understood. Factors influencing personalities include genetic background, prenatal (e.g. hormonal) and postnatal (e.g. environmental) conditions, and the strength of these factors can affect the consistency of personalities over time, and hence their flexibility in a changing environment. In birds, for example, hormones in eggs deposited by mothers can modulate aggressiveness of offspring and environmentally induced nutrition deficits in offspring can reduce neophobia later in life. Hence, investigating the fitness consequences of personalities requires the integration of physiological, behavioural and survival measures. We used the opportunity of a reintroduction project of grey partridge, Perdix perdix , to experimentally explore how multiple pre- and postnatal factors including measures of the hormone corticosterone were related to three behavioural traits. Then, we investigated whether the behaviours were repeatable and related to survival after release into the wild. Grey partridges showed distinct personalities affected by multiple pre- and postnatal factors. Proactive birds had low baseline levels of circulating corticosterone and survived longer after release into the wild compared to reactive and passive personalities. Consequently, the number of survivors after 6 months was substantially higher for proactive than for reactive and passive birds. Integrating data on behaviour, physiology and survival thus allows the investigation of the complex interplay of personality and fitness in a changing environment. • Animals have personalities but what are their fitness consequences in the wild? • We explored factors relating to behaviour of grey partridge bound for release. • Genetic, physiological, individual and social factors affected personalities. • After release, bold birds survived longer than passive and shy individuals. • Integration data on behaviour and physiology can support reintroduction outcome.