Periodic Reporting for period 1 - CitySleep (SLEEP IN THE CITY: How does artificial light at night affect EEG-based measures of sleep?)
Berichtszeitraum: 2018-04-01 bis 2020-03-31
Anthropogenic environments expose organisms to an array of novel stressors such as light, noise, and chemical pollution. These disturbance factors may interfere with adaptive behaviors and activate stress responses, with deleterious fitness effects. Sleep is a fundamental component of animals’ daily life and sleep deprivation has well-documented deleterious effects on health status. Thus, a primary aim of this project was elucidating whether sleep disruption occurs as a consequence of exposure to light and noise pollution, using a model species, the great tit (Parus major). In addition, I explored how noise, light and chemical pollution affect other aspects of behavior and physiology in these songbirds, including underexplored effects on developing nestlings (e.g. telomere dynamics), and effects on sexual coloration and parental behavior in adults. Finally, I strove to elucidate intraspecific differences in sensitivity to disturbance. Animal personalities, or individually-repeatable differences in behavior, have now been widely documented and may affect sensitivity to disturbance, especially via hormonal correlates.
This project has yielded valuable results, which advance the state-of-the-art. First, results suggest that exposure to ALAN and anthropogenic noise have deleterious effects on developing organisms, providing motivation for mitigation policies. In addition, noise exposure did not affect all nestlings equivalently, suggesting that identifying individual traits that affect stress sensitivity is important to detecting effects of human disturbance. Second, research on adults demonstrated that sexually-selected, carotenoid-based coloration is reduced in birds breeding closer to roads and with higher feather metal concentrations, with important implications for sexual signaling dynamics in anthropogenic landscapes. In addition, the nature of the noise regime, personality type and sex interacted to predict effects of noise exposure on nestling provisioning behavior, again suggesting intraspecific variation in sensitivity to disturbance. Finally, despite significant individual level variation in the effect of ALAN on sleep, effects were not dependent on personality type, as characterized by novel environment exploration behavior. A study involving the effect of constant and variable anthropogenic noise regimes on sleep behavior is currently in the analysis stage.
This project has yielded valuable results, which advance the state-of-the-art. First, results suggest that exposure to ALAN and anthropogenic noise have deleterious effects on developing organisms, providing motivation for mitigation policies. In addition, noise exposure did not affect all nestlings equivalently, suggesting that identifying individual traits that affect stress sensitivity is important to detecting effects of human disturbance. Second, research on adults demonstrated that sexually-selected, carotenoid-based coloration is reduced in birds breeding closer to roads and with higher feather metal concentrations, with important implications for sexual signaling dynamics in anthropogenic landscapes. In addition, the nature of the noise regime, personality type and sex interacted to predict effects of noise exposure on nestling provisioning behavior, again suggesting intraspecific variation in sensitivity to disturbance. Finally, despite significant individual level variation in the effect of ALAN on sleep, effects were not dependent on personality type, as characterized by novel environment exploration behavior. A study involving the effect of constant and variable anthropogenic noise regimes on sleep behavior is currently in the analysis stage.
This project employed a combination of field experiments, correlational studies and laboratory work. I conducted a field experiment to examine how ALAN affects telomere length, physiological stress and body condition in great tit (Parus major) nestlings. On a related vein, I made use of a gradient in noise associated with a major freeway to correlationally examine the relationship between noise exposure, telomere shortening and body mass in nestlings. Nestling telomere length was measured using quantitative PCR, and corticosterone concentrations were measured from feather samples via radioimmunoassay. I also conducted a correlational study to elucidate the relationship between metal contamination, proximity to roads, and carotenoid- and melanin-based sexual coloration in adults, and an experimental study to examine effects of constant versus variable noise regimes on nestling provisioning behavior. For this experiment, I prioritized use of birds that were tested for novel environment exploration behavior (a well-characterised personality trait in great tits) during the winter. Finally, an experimental studies were conducted to examine the effects of ALAN and constant versus temporally variable traffic noise on sleep behavior, and whether effects are modified by personality type.
The major results of these studies follow. First, with respect to developmental effects, exposure to ALAN elevated physiological stress, or changed energetic dynamics, as indicated by elevated feather corticosterone concentrations. However, ALAN did not change rates of telomere shortening, suggesting that the combination of effects induced by light exposure has no net effect on telomere dynamics. In contrast, anthropogenic noise was correlated with shorter telomeres in the smallest members of broods, which may be especially sensitive to stress. In addition, variability in noise levels was positively associated with carotenoid-based coloration in nestlings, suggesting that both the mean and variance in noise levels have important biotic effects. Fledging success and recruitment rates were not associated with exposure to ALAN or noise. Second, with respect to effects in adults, both feather metal concentrations and distance to a road were associated with carotenoid-based coloration. Melanin-based coloration was highly repeatable between years, but was not associated with anthropogenic pollution. In addition, females and birds that explored a novel environment more rapidly reduced nestling provisioning rates more when exposed to noise than males and individuals with lower exploration scores, but these differences were only apparent in the case of more variable noise. Exposure to ALAN significantly disrupted sleep, but this effect was not contingent on personality type. The study on effects of constant and variable noise on sleep is currently in the analysis stage.
The major results of these studies follow. First, with respect to developmental effects, exposure to ALAN elevated physiological stress, or changed energetic dynamics, as indicated by elevated feather corticosterone concentrations. However, ALAN did not change rates of telomere shortening, suggesting that the combination of effects induced by light exposure has no net effect on telomere dynamics. In contrast, anthropogenic noise was correlated with shorter telomeres in the smallest members of broods, which may be especially sensitive to stress. In addition, variability in noise levels was positively associated with carotenoid-based coloration in nestlings, suggesting that both the mean and variance in noise levels have important biotic effects. Fledging success and recruitment rates were not associated with exposure to ALAN or noise. Second, with respect to effects in adults, both feather metal concentrations and distance to a road were associated with carotenoid-based coloration. Melanin-based coloration was highly repeatable between years, but was not associated with anthropogenic pollution. In addition, females and birds that explored a novel environment more rapidly reduced nestling provisioning rates more when exposed to noise than males and individuals with lower exploration scores, but these differences were only apparent in the case of more variable noise. Exposure to ALAN significantly disrupted sleep, but this effect was not contingent on personality type. The study on effects of constant and variable noise on sleep is currently in the analysis stage.
This project has advanced the state of the art by integrating behavioral ecology, physiology and genetic approaches to examine the effects of multiple anthropogenic disturbance factors across multiple life-history stages. In the first study to examine the effects of ALAN on wild nestling birds, I granted new insight into the effects of ALAN on developing organisms, specifically suggesting that physiological stress is induced without affecting telomere dynamics. My study on the relationship between anthropogenic noise and physiological stress in nestlings advanced on past research by considering variability in the noise environment and by testing for interactions with individual traits that could modify sensitivity to disturbance. The results of my research on the relationship between sexual coloration and exposure to anthropogenic pollution included the unique finding that carotenoid-based coloration is negatively related to proximity to a road. I am unaware of any past study testing for this relationship, and there is now an urgent need for more studies to test the generality of this result. Finally, my studies on the effects of anthropogenic noise on nestling provisioning and sleep behavior advance on past research by considering whether different noise regimes have distinct biological effects. Specifically, I tested the prediction that more variable noise regimes, which may be more likely to activate stress responses, have more pronounced effects than constant noise. This prediction was supported by results for provisioning behavior. By demonstrating diverse effects of anthropogenic disturbance on a common urban songbird, results highlight the need to be cognizant of human impacts on the environment and to strive to reduce deleterious impacts, to the extent possible. Many of the response variables measured, such as telomere length and sleep behavior, are highly conserved in vertebrates. Thus, taking measures to reduce deleterious effects in animals may also have positive effects on humans.