TESTING THE GENERALITY OF CIRCADIAN–LIGHT INTERACTIONS IN ESCAPE BEHAVIOR IN THE DIURNAL RODENT RHABDOMYS PUMILIO

Rapid escape from approaching threats must be both reliable and flexible, allowing animals to adapt their responses to environmental cues. Previous work from our lab in nocturnal laboratory and deer mice has shown that circadian time and ambient light level jointly shape escape behavior. When presented with overhead visual threats, mice escape faster and more vigorously during the day than at night, and dim light enhances escape responses, while artificial light at night (ALAN) reduces escape probability and slows fleeing. In diurnal species, the relationship between circadian phase, ambient light, and defensive behavior may differ fundamentally from nocturnal rodents, yet this remains largely unexplored. Here, we investigated escape behavior in Rhabdomys pumilio (African striped mice), a diurnal rodent, to test whether principles derived from nocturnal mice generalize across chronotypes. Animals were tested at two circadian phases—ZT02 (daytime) and ZT14 (nighttime)—under two ambient luminance conditions representing bright and dim environments. Preliminary experiments revealed that, in contrast to nocturnal mice, during ZT02 Rhabdomys escape faster and more vigorously under bright ambient light, whereas dim light slows responses. Furthermore, ALAN had a weaker effect on escape behaviour in diurnal compared to nocturnal rodents. Overall, artificial illumination modulated escape behavior in Rhabdomys but with different effects than in nocturnal mice. Ongoing electrophysiological recordings in the superior colliculus and periaqueductal grey will reveal differences in visual encoding, motor signals or both which underlie these distinct impacts of ambient light and circadian rhythm in nocturnal versus diurnal species.