Amphibians are one of the most nocturnal groups of vertebrates and sadly their numbers have declined with loss of wetland habitats, pollution and diseases, with the 2019 State of Nature Report showing a 13% further decline since only 1970.(1)

The latest organisation to lend their support to the Dark Skies Cumbria Project is the Cumbria Amphibian and Reptile Group (2), who highlighted recent studies assessing the impacts of light pollution on common toads (Bufo Bufo).

Pictured: Common toads (Bufo Bufo) Copyright Ian Brodie

In late spring adult toads emerge from their overwintering sites and start migrating towards the pond on mild, damp evenings. Toads tend to return to ancestral breeding ponds along the same routes each year and are risk of being killed on the roads.

Research published in 2019 and 2020(3) highlights the potentially significant impact of artificial light on these sensitive species. Researhers experimentally exposed adult breeding male Common Toads to different light intensities (Lux) for 20 days, to investigate their activity using infrared cameras. The artificial lighting reduced toad activity over 24 hours by 56% at 5 lux and by 73% at 20 lux. Other research showed that under artificial light conditions frogs and toads find it harder to detect their prey and lower activity rates shorten foraging time. The follow-on research examined the sexual behaviour and fertilisation success of common toads under different light intensities. There was a clear major effect upon mating success and the higher light intensity of 5 lux-exposed on males reduced their fertilisation rate by 25%.

These combined effects on male toads at the onset of and during the spring breeding period could impact the reproduction and ultimately lead to a reduction in fitness, and have a long-term negative effect on the health of overall populations.

Clearly the effect of lighting on these toads and all amphibians needs to be carefully considered.(4) 

(1). https://www.arc-trust.org/News/state-of-nature-2019-report-published

(2). https://groups.arguk.org/carg

(3). https://academic.oup.com/conphys/article/7/1/coz002/5307659?login=true and

https://www.sciencedirect.com/science/article/abs/pii/S0269749119358348?via%3Dihub

      NB. Body mass and food take were unaffected in this study due to its short time-limited duration.

(4). See also USA research findings highlight other wider potential effects: https://www.independent.co.uk/climate-change/news/toads-frogs-amphibians-lights-slow-growth-extinction-night-case-western-reserve-university-a8429511.html