Repeatable glucocorticoid expression is associated with behavioural syndromes in males but not females in a wild primate.

P J Tkaczynski,C Ross,A Maclarnon,J Lehmann,M Mouna,B Majolo

doi:10.1098/rsos.190256

Abstract

Behavioural syndromes are a well-established phenomenon in human and non-human animal behavioural ecology. However, the mechanisms that lead to correlations among behaviours and individual consistency in their expression at the apparent expense of behavioural plasticity remain unclear. The ‘state-dependent' hypothesis posits that inter-individual variation in behaviour arises from inter-individual variation in state and that the relative stability of these states within an individual leads to consistency of behaviour. The endocrine stress response, in part mediated by glucocorticoids (GCs), is a proposed behavioural syndrome-associated state as GC levels are linked to an individual's behavioural responses to stressors. In this study, in wild Barbary macaques (Macaca sylvanus), consistent inter-individual differences were observed in both sexes for GC activity (faecal glucocorticoid, fGC concentrations), but not GC variation (coefficient of variation in fGC concentrations). The expression of the behavioural syndrome ‘Excitability' (characterized by the frequencies of brief affiliation or aggressive interactions) was related to GC activity in males but not in females; more ‘excitable' males had lower GC activity. There was no relationship in females between any of the behavioural syndromes and GC activity, nor in either sex with GC variation. The negative relationship between GC activity and Excitability in males provides some support for GC expression as a behavioural syndrome-generating state under the state-dependent framework. The absence of this relationship in females highlights that state-behavioural syndrome associations may not be generalizable within a species and that broader sex differences in state need to be considered for understanding the emergence and maintenance of behavioural syndromes.

Highlights

The term ‘behavioural syndromes’ refers to suites of correlated behaviours that vary consistently between individuals across time and contexts [1,2,3,4,5,6]
To test the state-dependent model, we examined whether expression of the repeatable GC variables (GC activity and/or GC variation) were related to the expression of established behavioural syndromes in Barbary macaques
There was no evidence for consistent inter-individual differences in GC variation between males (RA < 0.001; p = 0.629; table 2 and figure 1c) nor between females (RA = 0.001; p = 0.348; table 2 and figure 1d)

Summary

Introduction

The term ‘behavioural syndromes’ refers to suites of correlated behaviours that vary consistently between individuals across time and contexts [1,2,3,4,5,6]. Consistency in behaviour and correlations between different behaviours are potentially maladaptive if this constrains an individual’s ability to adapt to a changing environment [7,8]. The ‘state-dependent’ model posits that inter-individual variation in behavioural repertoires arises from inter-individual variation in ‘state’ and that the relative stability of states can be related to intraindividual consistency in behaviours and correlations of behaviours [5,9,10,11]. Studies investigating endocrine factors and behavioural syndromes have often focused on the hormonal stress response via monitoring of cortisol and other glucocorticoids (GCs; [17,18,19,20]). Fluctuations in GC levels are expected to be closely linked with an individual’s response to its environment and to much of its activity, behaviour and, potentially correlations of behaviour in the form of behavioural syndromes. Certain patterns of behaviour have been framed as ‘coping styles’ to stressors: individuals with ‘proactive’ coping styles tend to be active and aggressive, and to have lower HPA activity and reactivity than ‘reactive’ individuals, which tend to use strategies to avoid confrontation [18,19,29]

Methods

Results

Conclusion