Differences in adrenocortical responses between urban and rural burrowing owls: poorly-known underlying mechanisms and their implications for conservation

The hypothalamus–pituitary–adrenal/interrenal (HPA) axis of vertebrates integrates external information and orchestrates responses to cope with energy-demanding and stressful events through changes in circulating glucocorticoid levels. Urbanization exposes animals to a wide variety of ever-changing stimuli caused by human activities that may affect local wildlife populations. Here, we empirically tested the hypothesis that urban and rural owls (Athene cunicularia) show different adrenocortical responses to stress, with urban individuals showing a reduced HPA-axis response compared to rural counterparts to cope with the high levels of human disturbance typical of urban areas. We applied a standard capture-restraint protocol to measure baseline levels and stress-induced corticosterone (CORT) responses. Urban and rural owls showed similar circulating baseline CORT levels. However, maximum CORT levels were attained earlier and were of lower magnitude in urban compared to rural owls, which showed a more pronounced and long-lasting response. Variability in CORT responses was also greater in rural owls and contained the narrower variability displayed by urban ones. These results suggest that only individuals expressing low-HPA-axis responses can thrive in cities, a pattern potentially mediated by three alternative and non-exclusive hypotheses: phenotypic plasticity, natural selection and matching habitat choice. Due to their different conservation implications, we recommend further research to properly understand wildlife responses to humans in an increasingly urbanized world.

Mother–infant cortisol attunement: Associations with mother–infant attachment disorganization

This study explores the conceptualization of mother–infant cortisol attunement both theoretically and empirically, and its association with mother–infant attachment disorganization. In a community sample (N = 256), disorganization and cortisol were assessed during the Strange Situation Procedure (SSP) at infant age 17 months. Salivary cortisol was collected at baseline, and 20 and 40 min after the SSP. We utilized three statistical approaches: correlated growth modeling (probing a simultaneous conceptualization of attunement), cross-lagged modeling (probing a lagged, reciprocal conceptualization of attunement), and a multilevel model difference score analysis (to examine the pattern of discrepancies in mother–infant cortisol values). Correlated growth modeling revealed that disorganized, relative to organized, dyads had significant magnitude of change over time, such that, among disorganized dyads, as mothers had greater declines in cortisol, infants had greater increases. The difference score analysis revealed that disorganized, relative to organized, dyads had a greater divergence between maternal and infant cortisol values, such that maternal values were lower than infant values. Disorganized attachment status was not significantly associated with attunement when conceptualized as reciprocal and lagged in the cross-lagged model. Findings suggest that mother–infant dyads in disorganized attachment relationships, who are by definition behaviorally misattuned, are also misattuned in their adrenocortical responses.