Could the detection of small rodents be improved? The case of Oligoryzomys flavescens, an orthohantavirus reservoir species, in a natural reserve immersed in an urban landscape

Detectability poses a common challenge faced by studies of small mammals. Traditional sampling methods use traps placed exclusively on the ground, which makes them less effective for monitoring species with climbing habits. The bias arising from imperfect detection may have important implications in pest assessment, epidemiological studies involving reservoirs, and conservation studies. In this study, we added above ground level (AGL) traps in the bushy or arboreal stratum to the conventional sampling protocol. Our objective was to evaluate whether the location of the traps influences the seasonal abundance pattern of Oligoryzomys flavescens, a scansorial rodent species identified as an orthohantavirus reservoir in the study area. Additionally, we evaluated the potential impact of various environmental variables on the capture probability of O. flavescens in different strata. Detectability of this rodent was significantly increased in traps placed AGL than at ground level (GL). However, trap placement level did not influence seasonal variation in O. flavescens abundance. Furthermore, the increase in herbaceous cover at ground level positively influenced the probability of capturing O. flavescens in traps placed AGL. Traditional sampling designs relying solely on GL traps may perform well for studies focused on the population dynamics of O. flavescens. Conversely, in areas where herbaceous vegetation facilitates connectivity between the ground and shrub layers, adding AGL traps in the sampling strategy can guarantee better results for studies that need to capture a large number of O. flavescens individuals (i.e., seroprevalence studies or investigations on movements).