Short-term use of space by a neotropical forest rodent, Proechimys semispinosus

We examined use of space by adult Proechimys semispinosus (Central American spiny rat) on a small island in the Panama Canal using radiotelemetry. The study was conducted with six males and six females during February and Mar ch when spiny rats were becoming reproductively active and food resources w ere scarce. Our study therefore spanned a potentially critical period in wh ich behavioral changes associated with establishment of territories would b e most likely to occur. However, home ranges of spiny rats overlapped broad ly, and we found no evidence of territoriality. We detected four cases of a male co-occupying a burrow with a female, and one case in which two males co-occupied a burrow. Broadly overlapping home ranges, low nest-site fideli ty, and nest-site co-occupancy of single females with more than one male in a short period of time suggested that P. semispinosus on this island had a promiscuous mating system. However, the mating system of this species may vary with density, ranging from facultative monogamy at low densities to pr omiscuity at high densities.