93.4 Sunday, Jan. 6 Long-term effects of chronic artificial night light exposure on life-history traits of songbirds DOMINONI, DM*; PARTECKE, J; Max Planck Institute for Ornithology, Germany; Max Planck Institute for Ornithology, Germany firstname.lastname@example.org
We live in the urban millennium, the age of globalization and urban sprawl. Rapid expansion of cities is accompanied by extreme habitat change, and one of the most peculiar characteristics of urbanization is the presence of artificial light at night. However, little is known about the effects of light pollution on wild animals. We hypothesized that light at night may alter daylength perception and therefore modify seasonal timing. We experimentally tested our hypothesis using captive European blackbirds (Turdus merula) as model species. City and forest blackbirds were exposed to either dark nights or low light intensities at night (0.3 lux), and seasonal variation of testicular cycles, plasma testosterone and molt was determined for two consecutive years. In 2011, birds under light at night developed their testes up to one month earlier than control birds kept under dark nights. The same effect was detected in the timing of testosterone secretion and molt. Moreover, regardless of the light treatment city birds developed their testes earlier than forest conspecifics. In 2012, birds under light at night kept their reproductive system shut down for the entire spring and did not molt, whereas control birds showed the same timing of reproduction and molt of 2011, with city birds being earlier than forest birds. In conclusion, here we show that i) light at night can advance timing of reproduction and molt and ii) chronic and long-term exposition to light at night can suppress fitness-relevant life-history stages such as reproduction and molt. Our results emphasize the impact of human-induced lighting on the ecology of hundreds of millions of animals living in cities and call urgently for an understanding of the fitness consequences of light pollution.