To mitigate deforestation effects, reforestation programs with native and/or exotic species have been implemented in the Colombian Andes, but little is known about how such reforestations affect wildlife. Using camera-traps, we studied the species richness, activity patterns, and habitat use of middle and large mammals in two adjacent forests, a native forest and a Eucalyptus grandis reforestation located at the Colombian Central Andes. Since the two forests were adjacent, we expected no differences between species richness in the two forests. The reforestation was a monoculture and an artificial ecosystem, thus we expected differences in activity and habitat use by mammals in the two forest types. We did not find significant differences in the species richness between the forests. The activity of Sciurus granatensis and Mazama rufina was influenced by the time of the day, and there was a temporal and spatial segregation among the soil forager species Nasua nasua, Nasuella olivacea and Dasypus novemcinctus. The species N. nasua y D. novemcinctus used the Andean forest more than the reforestation, whereas N. olivacea used the reforestation more. D. novemcinctus and N. olivacea were mainly nocturnal and/or crepuscular, whereas N. nasua was mainly active during daytime. This suggests that the creation of a new habitat, such as the reforestation, might influence the interactions among some species and apparently, could reduce interspecific competition and thus contribute to their co-existence at the study zone though niche differentiation in time and space.