POPULATION-DYNAMICS OF DIDELPHIS-MARSUPIALIS IN NORTHERN COLOMBIA

A population of the common opossum, Didelphis marsupialis, inhabiting a highly degraded agricultural area in northern Colombia was studied b y live-trapping for over two years. Three transects were established i n strips of riparian vegetation within a matrix of agricultural crops. Sampling was performed once in October 1993 and then monthly from Aug ust 1994 through December 1995. Four population-level characteristics were estimated: abundance, sex ratio, age structure, and breeding acti vity. Abundance was very high at the beginning of the study but declin ed dramatically and then fluctuated at low numbers. The sex ratio did not vary among high-abundance, decline, and low-abundance population p hases, but there was a deficiency of females with young at high abunda nce and of adults during the decline. The impact of these characterist ics on the population dynamics of D. marsupialis is discussed with spe cial emphasis on reproductive traits. These characteristics may also c ontribute to the potential of D. marsupialis as a reservoir for a wide variety of infectious agents.