Does moonlight suppress or stimulate activity of a tropical forest small mammal

Small nocturnal mammals must balance their activity to maximize foraging efficiency while reducing vulnerability to predators, and moonlight has been widely investigated as a predation risk cue. Didelphis aurita, a nocturnal marsupial, can act as both a competitor and an intraguild predator, and as a prey, increasing or reducing activity under this condition, respectively. We evaluated the effect of moonlight, temperature, and age on the bimodal activity pattern of D. aurita in an Atlantic Forest area, southeastern Brazil. Opossums were more active at low light conditions and in colder nights in the second activity peak. Adults were more active in the second peak, when compared to juveniles and subadults. We suggest that the observed behavior can be a consequence of a preference to periods of low light conditions, to increase foraging efficiency, since D. aurita display features that reflect specialization to scotopic vision such as the tapetum lucidum.