Light Masking in the Field: An Experiment with Nocturnal and Diurnal Spiny Mice Under Semi-natural Field Conditions

Abstract

Light masking has been studied almost exclusively in the laboratory. The authors populated four field enclosures with locally coexisting nocturnal Acomys cahirinus and diurnal A. russatus, and monitored their body temperatures (T_b) using implanted temperature-sensitive radio transmitters. A 3-h light pulse was initiated at the beginning of two consecutive nights; preceding nights were controls. A. cahirinus T_b and calculated activity levels decreased significantly during the light pulse, demonstrating a negative light masking response (light effect on T_b: −0.32°C ± 0.15°C; average calculated activity records during the light pulse: 7 ± 1.53, control: 9.8 ± 1.62). Diurnal A. russatus did not respond to the light pulse. We conclude that light masking is not an artifact of laboratory conditions but represents a natural adaptive response in free-living populations. (Author correspondence: [email protected])

Keywords:

• Acomys
• Activity patterns
• Body temperature
• Field study
• Light masking
• Spiny mice
• adaptive response

ACKNOWLEDGMENTS

We thank G. Sterzer for her devoted assistance in conducting the field experiments, J. Kazes for his dedicated help in many field logistics issues, R. Cohen for her excellent help in animal surgery, other lab members, family, and friends who helped to construct the experimental set-up, the Israel Nature and Parks Authority for their help and friendship, and the Ein Gedi Field School of the Society for the Protection of Nature in Israel for their hospitality.

Declaration of Interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.