Corticosterone, Avoidance of Novelty, Risk‐Taking and Aggression in a Wild Bird: No Evidence for Pleiotropic Effects

Abstract

Certain inherent characteristics of individuals can determine both physiological and behavioural responses to environmental challenges, which could drive a correlation between levels of corticosterone (CORT), the most important stress hormone and behavioural profiles. Therefore, CORT level may mediate consistent behaviours along the shy/bold continuum, and thus, it could serve as a pleiotropic basis for behavioural syndromes. Moreover, behavioural responses to environmental challenges may have consequences for CORT concentrations, which would also result in a correlation between physiology and behaviours even without requiring pleiotropic mechanisms. Accordingly, we investigated the relationship between CORT and behaviour in free-living male collared flycatchers, Ficedula albicollis, using recently developed field assays. More specifically, we characterised novel object avoidance, intraspecific aggression and risk-taking in males and related these correlated behaviours to the concentration of CORT metabolites in droppings measured by enzyme immunoassay. Individuals with higher levels of excreted CORT metabolites had no consistently higher or lower behavioural scores along the shy/ bold spectrum, as avoidance of novelty, aggression and risk-taking were not systematically related to CORT metabolite concentrations in the same direction. Moreover, environmental challenges owing to the presence of a novel object, territorial intruder and a potential predator caused no elevation in the level of CORT metabolites. Therefore, we did not find correlative evidence for CORT driving correlated behaviours through pleiotropic effects or for particular behaviours during courtship causing elevation in CORT levels.

Evidence for a mechanism of phenotypic integration of behaviour and innate immunity in a wild rodent: implications for animal personality and ecological immunology

“…These results contradict the hypothesis that hormonal pleiotropies dictate evolutionary trajectories of behaviour and immunity, yet they provide evidence that even with independent evolutionary responses to differing selection pressures, hormonal pleiotropies dictate tradeoffs between behaviour and immunity. Field studies in western bluebirds, Sialia mexicana, and collared flycatchers, Ficedula albicollis, also did not find evidence for hormonal pleiotropies explaining animal personality (Duckworth & Sockman, 2012;Garamszegi et al, 2012), calling for additional tests of the hypothesis that assess other endocrine elements such as receptors.…”

“…animal personality) correspond to similar patterns of variation of immune traits described by the field of ecological immunology (Ardia, Parmentier, & Vogel, 2011;Schmid-Hempel, 2003;Sheldon & Verhulst, 1996). Researchers have questioned whether physiological mechanisms are responsible for these patterns of (co)variation, but the extent to which such mechanisms influence behavioural and immune variation and covariation remains unresolved (Ardia et al, 2011;Demas, Adamo, & French, 2011;Duckworth & Sockman, 2012;Garamszegi et al, 2012;Koolhaas, 2008;Krams et al, 2013;Sih et al, 2004). If multiple traits share a single mechanism, then that shared mechanism can facilitate functional integration of those traits or impede their independent expression, analogous to the pleiotropic effects that a single gene may have on multiple traits (Duckworth & Sockman, 2012;Garamszegi et al, 2012;Ketterson & Nolan, 1999;Krams et al, 2013).…”

“…However, many of these studies have focused on one type of trait, while research on glucocorticoidassociated phenotypic integration of suites of traits reveals that phenotypic independence is not uncommon (e.g. Buehler et al, 2012;Garamszegi et al, 2012;Koolhaas, De Boer, Coppens, & Buwalda, 2010). This may be because the actions of glucocorticoids have multiple pathways (Sapolsky et al, 2000).…”

“…Researchers have questioned whether physiological mechanisms are responsible for these patterns of (co)variation, but the extent to which such mechanisms influence behavioural and immune variation and covariation remains unresolved (Ardia et al, 2011;Demas, Adamo, & French, 2011;Duckworth & Sockman, 2012;Garamszegi et al, 2012;Koolhaas, 2008;Krams et al, 2013;Sih et al, 2004). If multiple traits share a single mechanism, then that shared mechanism can facilitate functional integration of those traits or impede their independent expression, analogous to the pleiotropic effects that a single gene may have on multiple traits (Duckworth & Sockman, 2012;Garamszegi et al, 2012;Ketterson & Nolan, 1999;Krams et al, 2013). By this reasoning, a number of traits may be relevant, but in this study we focus on relationships between behaviour and immunity because immunity is relatively understudied with respect to animal personality (but see Kluen, Siitari, & Brommer, 2014;Krams et al, 2013;Sild, Sepp, & Hõrak, 2011) and both are central to other hypotheses of trait covariation and maintenance of variance (e.g.…”

Evaluation of boldness assays and associated behavioral measures in a social parrot, monk parakeet (Myiopsitta monachus)

“…(1) Novel object tests simulate an encounter with an unfamiliar item, generally accompanying a food resource in the test arena (Wilson et al, 2010;Garamszegi et al, 2012). (2) Emergence tests focus on the propensity of individuals to leave a safe location and enter an unknown, potentially dangerous environment (Brown & Braithwaite, 2005;Miller et al, 2006).…”