Circadian use of time is an important, but often neglected, part of an animal's niche. We compared the activity patterns of the Neotropical otter Lontra longicaudis in two different areas in Brazil using camera traps placed at the entrance of holts. We obtained 58 independent photos in the Atlantic Forest (273 camera trap-days) and 46 photos in Pantanal (300 camera trap-days). We observed different kernel density probabilities on these two areas (45.6% and 14.1% overlap between the 95% and 50% density isopleths respectively). We observed the plasticity in Neotropical otter activity behaviour with different activity patterns in the two areas. In the Pantanal, the Neotropical otter selected daylight (Ivlev = 0.23) and avoided night (Ivlev = −0.44), while in the Atlantic Forest it selected dawn (Ivlev = 0.24) and night (Ivlev = 0.14), avoiding daylight (Ivlev = −0.33). We believe that this pattern can be due to human activity or shifts in prey activity.

Daily activity patterns reflect interactions between circadian mechanisms and environmental stimuli. Among these stimuli, temperature can be an important factor affecting activity budgets. To sample the agouti (Dasyprocta azarae), a systematic camera-trap grid was established with 50 independent sampling sites. A circular kernel function was used to characterize the activity patterns of the agouti population. To evaluate shifts in activity as a function of mean daily temperature, the entire set of records was subdivided into smaller sets covering different temperature ranges. The activity pattern belonging to each set was characterized and compared through the overlap of their full activity (95% isopleth) and activity core (50% isopleth). Based on 400 independent records, agoutis were predominately diurnal. They shifted their activity core, while keeping their activity range (the amount of time a population remains active during the 24-h cycle) constant through the temperature gradient. The agouti demonstrated a unimodal activity pattern at lower temperatures, which became more bimodal at higher temperatures. Nevertheless, it kept its activity range constant, regardless of temperature. These results likely reflect a trade-off between activity time and thermoregulation during the diurnal period and demonstrate how the agouti can change its behaviour to achieve thermal comfort.