Fuller, G., Raghanti, M. A., Dennis, P. M. et al. 2016. A comparison of nocturnal primate behavior in exhibits illuminated with red and blue light. Applied Animal Behaviour Science 184, 126-134.
Over evolutionary time, light from the sun, moon, and stars has provided organisms with reliable information about the passage of time; but modern artificial lighting has drastically altered these cues. Evidence is accumulating that exposure to light at night—particularly blue wavelengths—from computer screens, urban light pollution, or as an occupational hazard of night-shift work has major implications for human health. Nocturnal animals in zoos are generally housed on reversed light cycles and are illuminated by blue or red artificial light so that daytime visitors can observe their active behaviors. However, previous research suggests that exposure to light all 24h of the day and exposure to blue light during the dark phase can be harmful to human and animal health. Information about the consequences of lighting design for animal health and behavior is needed to formulate evidence-based guidelines for the exhibition of nocturnal animals in zoos. This study was conducted with nocturnal strepsirrhines at two facilities, one where the standard practice was to house nocturnal primates under blue light, and the other red. We experimentally changed the color of light illuminating habitats during the dark phase using an ABA study design and recorded continuous behavior data. We hypothesized that activity levels and time allocated to specific active behaviors would be lower under blue light compared to red. The overall percent of time spent performing active behaviors was lower when subjects were housed under blue light compared to red (generalized linear mixed models: pottos (N=4), F1,1169=54.0, p<0.001; pygmy slow lorises (N=2), F1,689=26.4, p<0.001; moholi bushbabies (N=2), F1,482=99.1, p<0.001; and aye-aye (N=1), F1,312=8.4, p=0.005). These changes were largely due to increased time spent moving around exhibits and examining objects under red light. We were also able to measure concentrations of the timekeeping hormone melatonin in the saliva of the aye-aye and found that levels were significantly lower in blue light compared to red (F1,85=18.0, p<0.001). These results offer a compelling reason to reconsider the practice of exhibiting nocturnal animals under blue light, as wavelength-dependent suppression of behavior and hormones may have important implications for animal health and welfare.