Effects of Artificial Light at Night on the Behaviour and Physiology of Free-living Songbirds
25 May 2018
Campus Drie Eiken, Promotiezaal Q0.02 - Universiteitsplein 1 - 2610 Antwerpen-Wilrijk (route: UAntwerpen, Campus Drie Eiken
Organization / co-organization:
Department of Biology
Marcel Eens & Rianne Pinxten
PhD defence Thomas Raap - Faculty of Science, Department of Biology
Urbanization is a serious threat to biodiversity affecting various biological processes. It has a wide range of impacts including habitat destruction and degradation, and exposure to chemical, noise and light pollution. Compared to other stressors, light pollution has until recently received relatively little attention. Artificial light at night (ALAN) has provided substantial benefits to humankind, such as extending the time that can be used for work. However, ALAN also disrupts circadian rhythms such as sleep and can lead to a multitude of direct and indirect physiological consequences. The biological consequences of ALAN are primarily studied under laboratory settings and comparable research on free-living animals is urgently needed as environmental conditions outside of the laboratory may affect behaviour and physiology.
The general aim of this research was to gain fundamental insights into the behavioural and physiological effects of ALAN in free-living animals. Great tits, and to a lesser extent blue tits, were used as model species. This PhD is primarily based on experimental work in which we illuminated the inside of nest boxes in which these cavity nesting birds roost and breed using a newly developed LED lighting system. For our experiments we investigated potential changes in behaviour and physiology from a dark night compared to when animals were exposed to ALAN for one or two nights, depending on the experiment.
From our experiments it became clear that ALAN disrupts sleep behaviour of free-living birds and that these effects are more pronounced during the breeding season. Interestingly, while great and blue tits are ecologically closely related species, the sleep behaviour of great tits was more disrupted by ALAN than that of blue tits. We found that after only two nights of ALAN exposure nestlings did no longer gain any body mass and haptoglobin and nitric oxide, two important measures of physiological condition and immunity, were also affected. However, oxidative status, which is related to life-history trade-offs, was unaffected. Furthermore, while physiology and condition of developing great tits was affected by experimental ALAN inside their nest box, ambient light pollution was unrelated to our physiological measures. Noise pollution on the other hand was related to nestling haptoglobin concentrations.
Sleep disruption by ALAN may eventually be detrimental for an individual’s health. Furthermore, the physiological effects during development may negatively affect short and long-term survival. Taken together, given that ALAN is steadily increasing even with the use of energy efficient LED lights, it is now vitally important to experimentally examine how long-term exposure to ALAN impacts behaviour and physiology and ultimately reproduction and survival and how these effects can be mitigated.