Oosthuizen et al. Data.pdf

Multimammate mice from the genus <i>Mastomys</i> are the most widespread rodent complex in Africa. They are prolific breeders, occurring at high densities, can cause significant agricultural damage, and are reservoir hosts for a number of pathogens that can be transmitted to humans. Multimammate mice are nocturnal and given their success in urbanised environments, we were interested in how they would respond to increasingly bright anthropogenic spaces. We evaluated the locomotor activity of wild-caught southern multimammate mice (<i>Mastomys coucha</i>), under four treatments: in an outdoor enclosure with natural light and temperature fluctuations, in a laboratory under a standard 12h Light:12h Dark light regime, and two artificial light at night (ALAN) regimes (2 Lux) of varying proximity to the experimental animal cages. The study animals remained nocturnal for the duration of the experiments. They were more active under the laboratory conditions compared to the outdoor treatment. The mice reduced their activity under ALAN. When the night light originated remotely from a corner of the room, activity levels decreased by more than 50%, whereas under direct ALAN from above the cages, there was a 75% decrease in activity. The onset of activity was later during the two LAN treatments and resulted in increased activity during the light phase of the day. We concluded that <i>Mastomys coucha </i>is strongly averse to light and show severe behavioural and circadian responses to light at night. We predict that it is unlikely that <i>Mastomys</i> will flourish in cities, but that they could thrive in and around dark urbanised refugia with access to abundant food.