Rodents of the genus have been reported to be nocturnal with a bimodal activity pattern and to frequently change burrows. However, no studies to date have examined these ecological aspects with the use of radio-telemetry. Five were captured and radio-collared to study their activity patterns and burrowing ecology from 9 March to 15 April 2016. Nocturnal activity ranged between the hours of 18:00 and 05:00 with a probable reduction of activities between 20:00-23:00 and around 04:00 with diurnal activity between 06:00 and 17:00 h with a reduction of activity between 11:00 and 14:00. While the present study does confirm nocturnal activity and a bimodal pattern, this study also suggests greater diurnal activity as compared to previous studies. Additionally, data presented here also suggest that . may not change burrows as frequently as previously reported.

Small mammal communities in the Neotropics are composed largely of sigmodontine rodents. However, many questions regarding these communities remain unanswered, especially those pertaining to fine-scale sympatry and habitat selection. To address this, we examined sigmodontine community structure and vegetation in the western margin of the Upper Paraná Atlantic Forest and the southwestern-most extent of the Cerrado (CE) (an extensive South American savanna ecoregion) of Paraguay. Vegetation classifications were derived from satellite imagery combined with maps based on extensive ground-based surveys. The three most abundant species (, , and ) were found most often in microsympatry with conspecifics, and were negatively associated with other species. was associated with high forest (HF), and with bamboo understory (BU), whereas did not exhibit a habitat preference. The first two species' distributions within the landscape were found to be driven primarily by habitat selection, and by a behavioral response (avoidance) to the presence of the other two species. Moreover, habitat influences whether or not a particular species associates with, or avoids, conspecifics or other species.