A light-exploiting insectivorous bat shows no melatonin disruption under lights with different spectra

Natural light-dark cycles synchronize an animal's internal clock with environmental conditions. The introduction of artificial light into the night-time environment masks natural light cues and has the potential to disrupt this well-established biological rhythm. Nocturnal animal species, such as bats, are adapted to low light conditions and are therefore among the most vulnerable to the impacts of artificial light at night (ALAN). The behaviour and activity of insectivorous bats is disrupted by short-wavelength artificial light at night, while long-wavelength light is less disruptive. However, the physiological consequences of this lighting have not been investigated. Here, we examine the effect of LEDs with different spectra on urinary melatonin in an insectivorous bat. We collected voluntarily voided urine samples from Gould's wattled bats (Chalinolobus gouldii) and measured melatonin-sulfate under ambient night-time conditions (baseline) and under red (λP 630 nm), amber (λP 601 nm), filtered warm white (λP 586 nm) and cool white (λP 457 nm) LEDs. We found no effect of light treatment on melatonin-sulfate irrespective of spectra. Our findings suggest that short-term exposure to LEDs at night do not disrupt circadian physiology in the light-exploiting Gould's wattled bat.