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Links between fear of humans, stress and survival support a non-random distribution of birds among urban and rural habitats.

Rebolo-Ifrán N, Carrete M, Sanz-Aguilar A, Rodríguez-Martínez S, Cabezas S, Marchant TA, Bortolotti GR, Tella JL - Sci Rep (2015)

Bottom Line: Recent research efforts have yielded controversial results based on short-term measures of stress, without exploring its fitness effects.FIDs were shorter in urban than in rural birds, but CORTf levels did not differ, nor were correlated to FIDs.These results evidence that urban life does not constitute an additional source of stress for urban individuals, as shown by their near identical CORTf values compared with rural conspecifics supporting the non-random distribution of individuals among habitats according to their behavioural phenotypes.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Ecología, Genética y Evolución &IEGEBA-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.

ABSTRACT
Urban endocrine ecology aims to understand how organisms cope with new sources of stress and maintain allostatic load to thrive in an increasingly urbanized world. Recent research efforts have yielded controversial results based on short-term measures of stress, without exploring its fitness effects. We measured feather corticosterone (CORTf, reflecting the duration and amplitude of glucocorticoid secretion over several weeks) and subsequent annual survival in urban and rural burrowing owls. This species shows high individual consistency in fear of humans (i.e., flight initiation distance, FID), allowing us to hypothesize that individuals distribute among habitats according to their tolerance to human disturbance. FIDs were shorter in urban than in rural birds, but CORTf levels did not differ, nor were correlated to FIDs. Survival was twice as high in urban as in rural birds and links with CORTf varied between habitats: while a quadratic relationship supports stabilizing selection in urban birds, high predation rates may have masked CORTf-survival relationship in rural ones. These results evidence that urban life does not constitute an additional source of stress for urban individuals, as shown by their near identical CORTf values compared with rural conspecifics supporting the non-random distribution of individuals among habitats according to their behavioural phenotypes.

No MeSH data available.


Distribution of feather CORT (CORTf) concentrations measured in urban (n = 109, black bars) and rural (n = 74, grey bars) burrowing owls.Overlapped, we show the relationship between CORTf and the estimated immediate survival of urban owls (black line, 95% CI depicted as dashed lines). There was not a significant relationship for rural individuals (see Results).
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f3: Distribution of feather CORT (CORTf) concentrations measured in urban (n = 109, black bars) and rural (n = 74, grey bars) burrowing owls.Overlapped, we show the relationship between CORTf and the estimated immediate survival of urban owls (black line, 95% CI depicted as dashed lines). There was not a significant relationship for rural individuals (see Results).

Mentions: The effect of CORTf on survival was retained in model selection (Table 3). The best supported model in terms of AICc (Model 1a, Table 3) showed that survival decreased with CORTf levels in rural birds (logit ϕrural = 1.851 (CI: −1.846–5-548)–0.382 (CI: −0.815–0.052)*CORTf) while it exhibited a quadratic relationship in urban ones (logit ϕurban = −4.547 (CI: −8.424–−0.671) + 0.917 (CI: 0.189–1.644)*CORTf–0.034 (CI: −0.065–−0.004)*CORTf2). However, the confidence interval for the beta estimate corresponding to the linear slope of rural birds included zero, indicating a non-significant effect. In fact, a more parsimonious model without this effect was equivalent in terms of AICc (ΔAICc = 1.90, Table 3), indicating that CORTf had a non-detectable effect on the survival of rural birds but a significant quadratic relationship in urban owls (logit ϕurban = −4.646 (CI: −8.493–−0.798) + 0.927 (CI: 0.205–1.650)*CORTf–0.034 (CI: −0.065–−0.004)*CORTf2). Accordingly, ∆AICc between models 1b and 1i (no CORTf effect on survival of rural and urban birds) was 5.38 (Table 3), supporting the CORTf-survival relationship in urban birds (Fig. 3). Therefore, in addition to habitat differences, CORTf had a significant effect on the survival of urban birds, with probabilities of survival being higher at intermediate CORTf levels (Fig. 3).


Links between fear of humans, stress and survival support a non-random distribution of birds among urban and rural habitats.

Rebolo-Ifrán N, Carrete M, Sanz-Aguilar A, Rodríguez-Martínez S, Cabezas S, Marchant TA, Bortolotti GR, Tella JL - Sci Rep (2015)

Distribution of feather CORT (CORTf) concentrations measured in urban (n = 109, black bars) and rural (n = 74, grey bars) burrowing owls.Overlapped, we show the relationship between CORTf and the estimated immediate survival of urban owls (black line, 95% CI depicted as dashed lines). There was not a significant relationship for rural individuals (see Results).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4562227&req=5

f3: Distribution of feather CORT (CORTf) concentrations measured in urban (n = 109, black bars) and rural (n = 74, grey bars) burrowing owls.Overlapped, we show the relationship between CORTf and the estimated immediate survival of urban owls (black line, 95% CI depicted as dashed lines). There was not a significant relationship for rural individuals (see Results).
Mentions: The effect of CORTf on survival was retained in model selection (Table 3). The best supported model in terms of AICc (Model 1a, Table 3) showed that survival decreased with CORTf levels in rural birds (logit ϕrural = 1.851 (CI: −1.846–5-548)–0.382 (CI: −0.815–0.052)*CORTf) while it exhibited a quadratic relationship in urban ones (logit ϕurban = −4.547 (CI: −8.424–−0.671) + 0.917 (CI: 0.189–1.644)*CORTf–0.034 (CI: −0.065–−0.004)*CORTf2). However, the confidence interval for the beta estimate corresponding to the linear slope of rural birds included zero, indicating a non-significant effect. In fact, a more parsimonious model without this effect was equivalent in terms of AICc (ΔAICc = 1.90, Table 3), indicating that CORTf had a non-detectable effect on the survival of rural birds but a significant quadratic relationship in urban owls (logit ϕurban = −4.646 (CI: −8.493–−0.798) + 0.927 (CI: 0.205–1.650)*CORTf–0.034 (CI: −0.065–−0.004)*CORTf2). Accordingly, ∆AICc between models 1b and 1i (no CORTf effect on survival of rural and urban birds) was 5.38 (Table 3), supporting the CORTf-survival relationship in urban birds (Fig. 3). Therefore, in addition to habitat differences, CORTf had a significant effect on the survival of urban birds, with probabilities of survival being higher at intermediate CORTf levels (Fig. 3).

Bottom Line: Recent research efforts have yielded controversial results based on short-term measures of stress, without exploring its fitness effects.FIDs were shorter in urban than in rural birds, but CORTf levels did not differ, nor were correlated to FIDs.These results evidence that urban life does not constitute an additional source of stress for urban individuals, as shown by their near identical CORTf values compared with rural conspecifics supporting the non-random distribution of individuals among habitats according to their behavioural phenotypes.

View Article: PubMed Central - PubMed

Affiliation: Departamento de Ecología, Genética y Evolución &IEGEBA-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.

ABSTRACT
Urban endocrine ecology aims to understand how organisms cope with new sources of stress and maintain allostatic load to thrive in an increasingly urbanized world. Recent research efforts have yielded controversial results based on short-term measures of stress, without exploring its fitness effects. We measured feather corticosterone (CORTf, reflecting the duration and amplitude of glucocorticoid secretion over several weeks) and subsequent annual survival in urban and rural burrowing owls. This species shows high individual consistency in fear of humans (i.e., flight initiation distance, FID), allowing us to hypothesize that individuals distribute among habitats according to their tolerance to human disturbance. FIDs were shorter in urban than in rural birds, but CORTf levels did not differ, nor were correlated to FIDs. Survival was twice as high in urban as in rural birds and links with CORTf varied between habitats: while a quadratic relationship supports stabilizing selection in urban birds, high predation rates may have masked CORTf-survival relationship in rural ones. These results evidence that urban life does not constitute an additional source of stress for urban individuals, as shown by their near identical CORTf values compared with rural conspecifics supporting the non-random distribution of individuals among habitats according to their behavioural phenotypes.

No MeSH data available.