Wild mice in an urbanized world: Effects of light at night under natural and laboratory conditions in the single-striped grass mouse (Lemniscomys rosalia).

Urbanization, and the accompanying artificial light at night (ALAN), can disrupt the activity of animals. Such disruptions at the base of a food web can ripple through the ecosystem. Most studies of ALAN are performed in the laboratory. Thus, we lack basic information about the circadian responses of animals under natural environmental conditions to fully evaluate the impact of ALAN. We studied the behaviour and activity of wild-caught, peri-urban single-striped grass mice (Lemniscomys rosalia) under a natural treatment and in a standard laboratory treatment, including dim light at night to mimic conditions that they could experience. The species exhibited predominantly crepuscular activity under all experimental treatments. It showed the highest level of activity under the natural treatment, whereas ALAN significantly suppressed its activity. Males were more active than females under all experimental treatments. The marked changes in activity under ALAN is of particular concern since global change in combination with urbanization can lead to a change in vegetation density and composition that will decrease the number of suitable microhabitats and expose small mammals to novel habitat changes. We suggest that the single-striped mice could become vulnerable because of urbanization, leading to impacts on its ecosystem broadly.

Learning and laterality in wild-caught Namaqua rock mice (Micaelamys namaquensis).

Individuals often exhibit differences in cognition and/or preferences for one side over the other. Such differences have been attributed to the mating system and lateralization of the brain hemispheres that can differ between the sexes, respectively. Despite the hypothesized significant effects on fitness, only a limited number of rodent studies addresses sex differences in laterality and most focus on laboratory rodents. Here we examined whether wild-caught Namaqua rock mice (Micaelamys namaquensis), a rodent widespread in sub-Saharan Africa, exhibit sex differences in learning and laterality in a T-maze. Food-deprived animals entered the maze significantly faster over subsequent learning trials, suggesting that the sexes learned to find the food reward at the end of the maze arms equally. Although we could not confirm a side preference at the population level, the animals were strongly lateralized at an individual level. When the sexes were considered separately, females exhibited a preference for the right maze arm while the opposite was observed in males. The lack of comparable studies of sex-specific lateralization patterns in rodents makes the generalization of our results challenging and highlights the need for more such studies in rodents at both the individual and population levels.