An animal’s biological clock, synchronized by the light and dark cycles in nature, enables many animals to anticipate and prepare for the cyclic changes in their environment. Today, in many habitats, due to the increasing use of artificial lighting, light has become an unreliable signal of day and night and even of the season of the year.

Such light pollution has a significant potential to affect an animal’s biological clock and, as a result, its behaviour, physiology and ecology. The effect of lighting regimes on amphibians has been little studied, and therefore has been the focus of the research carried out by Yael Ballon, currently completing her MSc degree and continuing to a doctorate, supervised by Prof. Noga Krofeld-Shor. Yael investigated the importance of light in determining the behavioural patterns and physiology of the spadefoot toad on a daily and seasonal scale. As part of the research, the activity levels of toads from our breeding colony in the Zoological Garden were measured using a dedicated camera system developed by Yael. The system documents the toads’ movement and activity in light, temperature and moisture controlled chambers. These parameters are measured under different lighting regimes, as well as in response to light pulses given during the night hours, in order to study the potential effects of light pollution. In addition, comparisons have been made between toads assigned to either a short or long daylight regime, and the influence of day length on the toad's aestivation has been studied. 

The results of the study indicate a possible strong influence of artificial lighting on the biological clock of the spadefoot toad. Light pollution penetrates most habitats, especially winter ponds – the spadefoot toads’ habitat – and its influence on the biology of this species could thus be significant. The findings are expected to have implications for nature conservation, urban planning policy and the construction of artificial winter ponds.

The breeding colony of the spadefoot toad, photo: Yael Ballon

The breeding colony of the spadefoot toad, photo: Yael Ballon  

About