Mean fecal glucocorticoid metabolites are associated with vigilance, whereas immediate cortisol levels better reflect acute anti-predator responses in meerkats

Abstract

Adrenal hormones likely affect anti-predator behavior in animals. With experimental field studies, we first investigated associations between mean fecal glucocorticoid metabolite (fGC) excretion and vigilance and with behavioral responses to alarm call playbacks in free-ranging meerkats (Suricata suricatta). We then tested how vigilance and behavioral responses to alarm call playbacks were affected in individuals administered exogenous cortisol. We found a positive association between mean fGC concentrations and vigilance behavior, but no relationship with 2 the intensity of behavioral responses to alarm calls. However, in response to alarm call playbacks, individuals administered cortisol took slightly longer to resume foraging than control individuals treated with saline solution. Vigilance behavior, which occurs in the presence and absence of dangerous stimuli, serves to detect and avoid potential dangers, whereas responses to alarm calls serve to avoid immediate predation. Our data show that mean fGC excretion in meerkats was associated with vigilance, as a re-occurring anti-predator behavior over long time periods, and experimentally induced elevations of plasma cortisol affected the response to immediate threats. Together, our results indicate an association between the two types of anti-predator behavior and glucocorticoids, but that the underlying mechanisms may differ. Our study emphasizes the need to consider appropriate measures of adrenal activity specific to different contexts when assessing links between stress physiology and different anti-predator behaviors.

Family-transmitted stress in a wild bird

“…supports previous studies in other vertebrate species (e.g., 13,14) and emphasizes the adaptive value of stress responses for promoting short-term survival (9). Importantly, our results suggest that stress transfer from brood mates experiencing an external stressor (predator) in the shared environment may enhance the chance of coping with this stressor (antipredator behavior) in brood mates that did not directly receive the stimuli.…”

“…9 and 12). For instance, exposure to predators causes elevation of stress hormones, which in turn enhances antipredator responses such as increased vigilance and fast reaction against predators (13,14), thereby promoting short-term survival (4).…”

Meerkat close calling patterns are linked to sex, social category, season and wind, but not fecal glucocorticoid metabolite concentrations

“…Several studies have shown that high arousal and stressful states, which are assumed to increase GC concentrations, can affect vocal production in vertebrates [3, 4, 26–29]. For instance, fundamental frequency (F0), the lowest frequency of a periodic waveform, tends to be higher in calls produced in high-arousal contexts, such as during encounters with predators [2, 30]. However, these studies have not monitored concentrations of GCs or their excreted metabolites, and it is unclear whether there is a direct link between GC output and vocal production, or whether GCs association to acoustic changes is mediated by other components of an individual’s physiological stress response [30].…”

“…Dominant females also behave more aggressively in food competition contexts during reproductive periods, presumably as a result of their higher energetic needs [39, 40]. Mean fGCM levels (with a temporal delay of about 24 hrs in meerkats reflecting plasma cortisol concentrations [33]) are associated with higher reproductive rates [11] and with vigilance behavior [30]. Meerkats reach sexual maturity around one year of age, although they continue to grow for a while longer [42].…”

Glucocorticoids mediate egg rejection in a brood parasite host

“…Specifically, we experimentally lowered plasma glucocorticoid levels using mitotane injections in an egg-46 rejecter host species and asked whether this treatment shifted the probability of non-mimetic foreign egg 47 rejection compared to a sham-treatment. Because corticosterone can mediate vigilance in vertebrates [14] 48 and suppress parental behaviours in birds [15,16], we predicted that inhibition of glucocorticoid synthesis 49 would reduce foreign egg rejection. 50 51 2.…”