Relationships between personality traits and the physiological stress response in a wild mammal

Abstract

Glucocorticoids (GCs) are involved in the regulation of an animal’s energetic state. Under stressful situations, they are part of the neuroendocrine response to cope with environmental challenges. Animals react to aversive stimuli also through behavioral responses, defined as coping styles. Both in captive and wild populations, individuals differ in their behavior along a proactive–reactive continuum. Proactive animals exhibit a bold, active-explorative and social personality, whereas reactive ones are shy, less active-explorative and less social. Here, we test the hypothesis that personality traits and physiological responses to stressors covary, with more proactive individuals having a less pronounced GC stress response. In wild populations of invasive gray squirrels Sciurus carolinensis, we measured fecal glucocorticoid metabolites (FGMs), an integrated measure of circulating GCs, and 3 personality traits (activity, sociability, and exploration) derived from open field test (OFT) and mirror image stimulation (MIS) test. Gray squirrels had higher FGMs in Autumn than in Winter and males with scrotal testes had higher FGMs than nonbreeding males. Personality varied with body mass and population density. Squirrels expressed more activity-exploration at higher than at lower density and heavier squirrels had higher scores for activity-exploration than animals that weighed less. Variation in FGM concentrations was not correlated with the expression of the 3 personality traits. Hence, our results do not support a strong association between the behavioral and physiological stress responses but show that in wild populations, where animals experience varying environmental conditions, the GC endocrine response and the expression of personality are uncorrelated traits among individuals.

Measuring personality traits in Eurasian red squirrels: A critical comparison of different methods

“…Personality traits activity and immobility, measured in the OFT, had a moderate repeatability, suggesting they are reliable personality traits for red squirrels, in both alpine and plain sites (Brehm & Mortelliti, 2018; Carter et al., 2013). This is similar to other studies on the same species, where repeatabilities for activity and immobility were also moderate (Mazzamuto et al., 2019; Santicchia, Wauters, Piscitelli, et al., 2020; Wauters et al., 2019), and on other studies on rodents where repeatability of activity measured in the OFT were from moderate to high ( Tamiasciurus hudsonicus : Boon et al., 2008; Tamias striatus : Montiglio et al., 2012; Sciurus carolinensis: Mazzamuto et al., 2019, Santicchia, Wauters, Dantzer, et al., 2020; Marmota flaviventer : Petelle et al., 2019; Peromyscus maniculatus , Myodes gapperi , Blarina brevicauda: Brehm et al., 2019, Brehm et al., 2020).…”

“…Recent studies on rodents measured exploration in the OFT using different variables, such as duration or frequency of behaviours observed, and reported repeatabilities from low to moderate ( Marmota flaviventer : Petelle et al., 2019; Myodes glareolus : Schirmer et al., 2019). Previous studies on the same species and on a different squirrel species also found low repeatability values for exploration measured in the OFT ( Sciurus vulgaris : Santicchia, Wauters, Piscitelli, et al., 2020; Wauters et al., 2019; Sciurus carolinensis : Santicchia, Wauters, Dantzer, et al., 2020) and among‐individual variation in the duration of exploration behaviours in the OFT was low, compared to other behavioural measures taken during the same tests (see Table S2; Santicchia, Wauters, Dantzer, et al, 2020; Table 1; Santicchia, Wauters, Piscitelli, et al., 2020; Table 2; Wauters et al., 2019). Hence, behaviours related to pure exploration by this species occur rarely in such tests.…”

“…Hence, separating exploration from activity is critical and not always possible, since they are strongly and positively associated in several squirrel species (Boon et al., 2008; Boyer et al., 2010; Martin & Réale, 2008; Patterson & Shulte‐Hostedde, 2011). This highlights how, in different squirrel species, the OFT might not be the best way to measure exploration separately from activity (Boon et al., 2008; Boyer et al., 2010; Martin & Réale, 2008; Santicchia, Wauters, Dantzer, et al., 2020; Santicchia, Wauters, Piscitelli, et al., 2020; Wauters et al., 2019).…”

Investigating Personality in Polar Bears Using the Concept of Behavioral Instability

“…It has for several species been shown that conspecific individuals have different personalities [1,2]. These different personalities are expressed by consistent behavioral responses under various conditions, that can vary with different variables e.g.…”

“…These different personalities are expressed by consistent behavioral responses under various conditions, that can vary with different variables e.g. population density, stress and enrichment [2,3,4]. The personality of an animal can influence its welfare, as these responses can vary between individuals, i.e.…”