Sampling allows assessing the impact of human activities on mammal communities. It is also possible to assess the accuracy of different sampling methods, especially when the sampling effort is similar. The present study aimed at comparing two mammalian surveys carried out over a three-year interval, in terms of sampling effort, capture success, abundance of domestic dogs, impact of human activities, and relative biomass using camera traps, in the Serra do Japi Biological Reserve and surroundings, located in Jundiaí, state of São Paulo, southeastern Brazil. The total richness recorded was 13 species, one domestic and 12 wild mammals. Sampling effort in both surveys was similar, but capture success and number of captures differed. The abundance of wild mammals and dogs did also differ between surveys. There was a highly significant correlation between abundance of wild mammals and capture effort for the survey performed in 2006/2007, but not for the survey performed in 2009/2010. The difference between samples may be related to human disturbance, since the number of domestic mammals photographed was higher in the second survey, three years after the first survey. Despite being a reserve, the area is still under pressure from urbanization, biological invasion, environmental degradation, and hunting, which may reduce the abundance of wild mammals.