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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.


Relationships between feather CORT (CORTf) and FID of urban (grey dots) and rural (white dots) adult burrowing owls.In the external margins of the plot, we included the boxplots for FID and CORTf of rural (n = 49) and urban (n = 72) birds.
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f1: Relationships between feather CORT (CORTf) and FID of urban (grey dots) and rural (white dots) adult burrowing owls.In the external margins of the plot, we included the boxplots for FID and CORTf of rural (n = 49) and urban (n = 72) birds.

Mentions: According to previous studies, urban burrowing owls showed significantly shorter FIDs than their rural conspecifics (urban birds: mean = 18.29 m, SE = 1.05, n = 72; rural birds: mean = 54.51 m, SE = 3.83, n = 49), even while controlling for the slightly shorter -although not statistically significant- FIDs in males (mean = 31.19 m, SE = 3.49, n = 56) than in females (mean = 34.48 m, SE = 3.12, n = 65) (Table 1). However, this closer interaction with humans does not suppose an extra-source of stress, as urban birds showed nearly identical CORTf concentrations than rural ones (urban birds: mean = 9.61 pg/mm, SE = 0.38, n = 72; rural birds: mean = 9.57 pg/mm, SE = 0.33, n = 49, Fig. 1). CORTf did not differ between habitat types even when controlling for year and the slightly and marginally significant lower CORTf concentrations found in males (mean = 9.01 pg/mm, SE = 0.29, n = 56) than in females (mean = 10.10 pg/mm, SE = 0.40, n = 65; Table 1). Moreover, CORTf concentrations were not related to individual FIDs, either when considering all birds together (Table 1) or when taking into account potential differences between habitats (interaction habitat *FID: F1,115 = 0.05, p = 0.82; Fig. 1).


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)

Relationships between feather CORT (CORTf) and FID of urban (grey dots) and rural (white dots) adult burrowing owls.In the external margins of the plot, we included the boxplots for FID and CORTf of rural (n = 49) and urban (n = 72) birds.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f1: Relationships between feather CORT (CORTf) and FID of urban (grey dots) and rural (white dots) adult burrowing owls.In the external margins of the plot, we included the boxplots for FID and CORTf of rural (n = 49) and urban (n = 72) birds.
Mentions: According to previous studies, urban burrowing owls showed significantly shorter FIDs than their rural conspecifics (urban birds: mean = 18.29 m, SE = 1.05, n = 72; rural birds: mean = 54.51 m, SE = 3.83, n = 49), even while controlling for the slightly shorter -although not statistically significant- FIDs in males (mean = 31.19 m, SE = 3.49, n = 56) than in females (mean = 34.48 m, SE = 3.12, n = 65) (Table 1). However, this closer interaction with humans does not suppose an extra-source of stress, as urban birds showed nearly identical CORTf concentrations than rural ones (urban birds: mean = 9.61 pg/mm, SE = 0.38, n = 72; rural birds: mean = 9.57 pg/mm, SE = 0.33, n = 49, Fig. 1). CORTf did not differ between habitat types even when controlling for year and the slightly and marginally significant lower CORTf concentrations found in males (mean = 9.01 pg/mm, SE = 0.29, n = 56) than in females (mean = 10.10 pg/mm, SE = 0.40, n = 65; Table 1). Moreover, CORTf concentrations were not related to individual FIDs, either when considering all birds together (Table 1) or when taking into account potential differences between habitats (interaction habitat *FID: F1,115 = 0.05, p = 0.82; Fig. 1).

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.