Diversity and abundance of small mammals in degraded tropical dry forest of northern Colombia

An area of highly disturbed tropical dry forest in Cordoba Department, northern Colombia was censused by live-trapping for 17 months to examine diversity, abundance, and population dynamics of opossums and rodents in this habitat type. Three sampling transects were established along narrow corridors of second-growth vegetation extending into an agricultural landscape. An initial census was conducted in October 1993, and monthly censuses were conducted from August 1994 through December 1995. Two species of opossums (Didelphis marsupialis and Marmosa robinsoni) and five species of rodents (Sciurus granatensis, Heteromys anomalus, Oecomys concolor, Zygodontomys brevicauda, and Proechimys canicollis) were captured during the study. Relative abundances of D. marsupialis, H. anomalus, and Z. brevicauda were extremely high during the initial census and at the beginning of the monthly censuses but declined dramatically thereafter and fluctuated erratically through the remainder of the study. These results suggest that the disturbed habitat supports a small-mammal fauna of low diversity. However, several of the species appear to have benefitted from forest clearance and agricultural activities and may occasionally reach extremely high numbers. While abundances may be very high, populations are not stable and may exhibit large-scale fluctuations in abundance.