A project undertaken at the Department of Ecology, Environment & Evolution, La Trobe University and supervised by Kylie Robert
Background
Artificial lighting can alter the timing of breeding in many wild animals. Change in day length is an important cue for reproductive activation in seasonal breeders to ensure optimal timing of greatest maternal investment with favourable environmental conditions (high resources). We found that artificial lighting in urbanised areas masked seasonal changes in ambient light cues resulting in suppressed melatonin levels and delayed births in free-ranging Tammar wallabies. Despite numerous species co-occurring with humans in urban environments, no study has previously documented the effects of human-made light pollution at night on free-ranging mammals. With a global increase in energy-efficient light sources such as white light-emitting diodes (LEDs) there is great concern for circadian pattern disruption in wildlife resulting in impaired immunity, survival and reproduction. This project will experimentally test long and short wavelength LED lighting on species with the aim of developing “wildlife friendly” outdoor lighting that will have direct management applications.
Figure 1. Seasonally breeding Tammar wallabies (Macropus eugenii) use light cues to signal reproductive activation. Artificial light at night interferes with this natural signal and delays activation. We are currently testing lights of different spectra to produce “wildlife friendly” lighting.
Figure 2. Study lighting installed in wallaby enclosures to test (A) white LED’s and (B) “wildlife friendly” LED’s. The spectral wavelengths for the (a) white LED’s and (b) “wildlife friendly” LED’s.lighting.
Objectives
- a.To develop and experimentally test “Wildlife Friendly” LED lighting as “proof of concept” in a seasonally reproductive mammal impacted by artificial light at night,
b. To determine cycling melatonin levels and reproductive activation under experimental light levels in a seasonally reproductive mammal impacted by artificial light at night, - Monitor the impacts of artificial light on wildlife using large-scale experimental lighting,
- Determine appropriate LED lighting in the future management of species in disturbed habitats.
Progress to date
We have completed the captive study developing and testing “Wildlife Friendly” LED lighting on wallabies (summary below). The results will be submitted as an honours thesis in August and presented at the Australian Mammal Society meeting in September.
We manipulated the spectral composition of LED lights as a means to mitigate the ecological and health consequences associated with their use. We experimentally investigated the impact of white LEDs (peak wavelength 448nm), long wavelength shifted amber LEDs (peak wavelength 605nm) and no lighting, on melatonin production, oxidative stress and circulating antioxidant capacity in the tammar wallaby (Macropus eugenii). Night-time melatonin and oxidative status were determined at baseline (day 0) and again after a 2- and 10-week exposure to light treatments. White LED exposed wallabies had suppressed nocturnal melatonin and elevated oxidative stress compared to no light and amber LED exposed wallabies, while there was no difference in antioxidant capacity. These results show for the first time, a negative effect on oxidative health and provide further evidence that short wavelength light at night suppresses nocturnal melatonin. However, we also illustrate that shifting the spectral output to longer wavelengths could mitigate these negative effects.