In the West Central Region of Costa Rica, there are plenty of forests under public and private protection; however, they are increasingly exposed to fragmentation. This is the first report about species richness and the relative abundance of large and medium size terrestrial mammals, in Alberto Manuel Brenes Biological Reserve (ReBAMB) and Nectandra Cloud Forest Reserve (RPN). Our camera trap study was undertaken between April and August, 2008. After 1 620 trap-days, 11 species were identified, nine in ReBAMB and six in RPN. The recorded species in both sites were: Cuniculus paca, Dasyprocta punctata, Nasua narica and Pecari tajacu. Felids were only captured in ReBAMB. The peccary (P. tajacu) was the most abundant mammal within the studied area, in contrast with the apparent absence of species such as white-lipped peccary (Tayassu pecari) and jaguar (Panthera onca). The difference in species composition between both sites was probably consequence of habitat fragmentation, which especially affects RPN. Species as white-lipped peccary and jaguar could be affected, directly or indirectly, by poaching. We propose that a good conservation goal for ReBAMB and due to their ecological importance is to have at least a white-lipped peccary’s population for the next ten years.

Keywords: mammals, abundance, species richness, camera-trap, Costa Rica