Home Range, Population Density, and Food Resources of Agouti paca (Rodentia: Agoutidae) in Costa Rica: A Study Using Alternative Methods 1

ABSTRACT Field studies of elusive mammals such as Agouti paca are difficult, and results are often biased and incomplete because the animals are nocturnal and avoid traps. By studying an A. paca population in a Pacific lowland forest of Costa Rica, we developed indirect observational methods to estimate population density and food resource utilization. To estimate population density, we divided the number of A. paca burrows found in a 12‐ha census area by the average number of burrows utilized per individual from radiotelemetry data. We compared this estimate to independent population estimates obtained using two transect methods. Agouti paca density was estimated at 93 individuals/km 2 based on burrow number, and between 67 to 70 individuals/km 2 using transect methods. This discrepancy corroborates previous studies suggesting that transect methods underestimate population density. To identify food resources consumed by the species, we collected fruits and seeds with unambiguous A. paca teeth marks. The only animal in Central America with an incisor width similar to A. paca. is Dasyprocta variegata; in a comparison of both species, however, we found that A. paca had a significantly larger incisor width and that teeth marks of 4 mm or wider unambiguously indicated handling by this species. By applying this technique, food resources utilized by A. paca can be identified more easily than by direct observation. At our study site, we identified 33 plant species consumed by A. paca; 61 percent are new records for this animal. Our results suggest that A. paca plays a major, although not fully understood, ecological role in seed predation and dispersal.