Modulation of heart rate responses to acute stressors throughout the breeding season in a colonial seabird, the king penguin

Abstract

ABSTRACT'Fight-or-flight' stress responses allow animals to cope adaptively to sudden threats by mobilizing energy resources and priming the body for action. Because such responses can be costly and redirect behavior and energy from reproduction to survival, they are likely to be shaped by specific life-history stages, depending on the available energy resources and the commitment to reproduction. Here, we consider how heart rate (HR) responses to acute stressors are affected by the advancing breeding season in a colonial seabird, the king penguin (Aptenodytes patagonicus). We subjected 77 birds (44 males, 33 females) at various stages of incubation and chick-rearing to three experimental stressors (metal sound, distant approach and capture) known to vary both in their intensity and associated risk, and monitored their HR responses. Our results show that HR increase in response to acute stressors was progressively attenuated with the stage of breeding from incubation to chick-rearing. Stress responses did not vary according to nutritional status or seasonal timing (whether breeding was initiated early or late in the season), but were markedly lower during chick-rearing than during incubation. This pattern was obvious for all three stressors. We discuss how 'fight-or-flight' responses may be modulated by considering the energy commitment to breeding, nutritional status and reproductive value of the brood in breeding seabirds.

Sex‐specific lateralization during aggressive interactions in breeding king penguins

“…We found that brooding king penguins initiated more agonistic interactions than incubating birds, which is consistent with previous findings (Côté, ) and with the idea that parents are willing to invest more into territorial defense with an increasing reproductive value of their chick (Côté, ; Viblanc, Dobson, et al, ; Viblanc, Gineste, et al, ; Viblanc, Smith, Gineste, Kauffmann, & Groscolas, ). Interestingly, brooding birds were also more strongly lateralized than incubating birds, which might be explained by a gradual increase in predation risk (e.g., by brown skuas) around the time of chick brooding (Descamps et al, ) (see c above).…”

“…Sex-dependent lateralization may then be an efficient way to confuse predators as to vigilance behavior related to visually active fields, all while being able to save energy for instance via unihemispheric sleep, a faculty known to exist only in birds and aquatic mammals (Rattenborg, Lima, & Amlaner, 1999). This is all the more relevant for breeding penguins where energy sparing of stored body reserves while fasting on-land is critical to successful breeding (Gauthier-Clerc, Maho, Gendner, Durant, & Handrich, 2001;Groscolas & Robin, 2001;Olsson, 1997 We found that brooding king penguins initiated more agonistic interactions than incubating birds, which is consistent with previous findings (Côté, 2000) and with the idea that parents are willing to invest more into territorial defense with an increasing reproductive value of their chick (Côté, 2000;Viblanc, Dobson, et al, 2016;Viblanc, Smith, Gineste, Kauffmann, & Groscolas, 2015). Interestingly, brooding birds were also more strongly lateralized than incubating birds, which might be explained by a gradual increase in predation risk (e.g., by brown skuas) around the time of chick brooding (Descamps et al, 2005) .…”

An integrative appraisal of the hormonal and metabolic changes induced by acute stress using king penguins as a model

“…acute stress responses (both HPA and sympathetic) and reactivity to external threats (Viblanc et al, 2016(Viblanc et al, , 2015(Viblanc et al, , 2014a(Viblanc et al, ,b, 2012a, possibly explaining the high inter-individual variability observed in our study. CORT plays major roles in the breeding cycle of penguins.…”

“…capture and restraint. Sympathetic heart rate responses to stress are stressor-specific in this species, and captures are known to elicit maximal adrenergic responses when compared to milder stressors such as loud sounds or distant human approaches (Viblanc et al, 2015(Viblanc et al, , 2012a. Whether HPA responses are also stressor-specific (e.g.…”

Quantifying the autonomic response to stressors – one way to expand the definition of "stress" in animals

“…Even then, the prognostic quality of 151 HR itself is tenuous in clinical medicine. In humans, a typical standard deviation of heart 152 rate can be up to 10 beats per minute, which is not itself significantly different from window into the stress state of an animal is challenging from a taxonomic, 163 environmental, circadian, and life history perspective, as they are all factors that affect 164 HR and HR-associated adaptations (Viblanc et al 2015). Therefore, a cardiac measure 165 that provides more resolution into the underlying physiology is required and may be 166 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 blood circulation and delivery of nutrients and glucose to peripheral organs.…”