Abstract
BackgroundBringing free-living animals into captivity subjects them to the stress of both capture and captivity, leading to the alteration of normal physiological processes and behaviors through activation of the hypothalamic–pituitary–adrenal axis. In free-living birds, although elevated plasma corticosterone (CORT) is an important adaptation regulating physiological and behavioral responses during the process of capture and captivity stress, little information is currently available on the effects of such stress on plasma metabolite levels.MethodsWe examined the effects of immediate capture and 24-h captivity on body mass, body condition, plasma CORT, and metabolite levels including glucose (Glu), triglyceride (TG), total cholesterol (TC), uric acid (UA), in breeding Eurasian Tree Sparrows (Passer montanus).ResultsCORT and Glu levels were increased significantly by the stress of capture, whereas TC and UA levels decreased. Body mass, body condition declined notably after 24 h in captivity, but CORT, Glu, and UA levels increased. Furthermore, male sparrows had lower TG levels after both capture and captivity than those of females. The relationships between plasma CORT and metabolite levels varied between sexes.ConclusionsOur results revealed that the metabolic status of Eurasian Tree Sparrows could be dramatically altered by capture and captivity. Monitoring the dynamic effects of both capture and captivity on plasma CORT, metabolite levels in a free-living bird contributes to a better understanding of the stress-induced pathways involved in sex-dependent energy mobilization.
Highlights
Bringing free-living animals into captivity subjects them to the stress of both capture and captivity, leading to the alteration of normal physiological processes and behaviors through activation of the hypothalamic– pituitary–adrenal axis
To determine the dynamic effects of both capture stress and subsequent captivity stress on plasma CORT and metabolites, we studied changes in plasma CORT, metabolite levels, including Glu, TG, total cholesterol (TC), and uric acid (UA), of breeding Eurasian Tree Sparrows (Passer montanus) that were subject to both the stress of capture in the field and a subsequent 24-h period in captivity
Post hoc results showed that both body mass and body condition decreased significantly during the 24-h period birds were held in captivity (Fig. 1a, b), and that female sparrows were in better condition than males (Fig. 1b)
Summary
Bringing free-living animals into captivity subjects them to the stress of both capture and captivity, leading to the alteration of normal physiological processes and behaviors through activation of the hypothalamic– pituitary–adrenal axis. Bringing free-living animals into captivity is frequently required for conservation, and for research in animal ecology, environmental physiology, and conservation biology (Dickens et al 2010; Mason 2010; Mason et al 2013; Dickens and Bentley 2014) This process subjects animals to both the acute stress of immediate capture and the chronic stress of captivity, resulting in the alteration. Plasma Glu response to capture stress varies with life-history stages in Rufous-winged Sparrows (Peucaea carpalis), i.e. not change in breeding stage, and decreased in molting and non-breeding stages (Deviche et al 2016a) The reason for this variability in plasma Glu regulation in free-living birds remains largely unknown. The confinement, unfamiliar and unnatural conditions experienced by freeliving animals in captivity can lead to the secretion of plasma GC and metabolites (e.g. Glu and TG), resulting in metabolic disorders, energetic stress and reduced fitness (Morgan and Tromborg 2007; Dickens et al 2009, 2010; Mason 2010; Fokidis et al 2011)
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