Diel activity guild drives different mammal responses to fragmentation and degradation in the Amazon deforestation arc

Abstract Fragmentation and degradation have profound effects on species’ habitat use and activity patterns. According to their diel activity guild, species may respond differently to environmental change, with diurnal species expected to be more vulnerable to these changes. Here, we test this hypothesis by investigating how fragmentation, and degradation modulate the habitat use and overlap in diel activity of contrasting mammal diel activity guilds in the Amazonian arc of deforestation. We used data from camera-traps (2,970 trap-days) across 30 forest fragments (from 8 to 435 ha) and three continuous forest sites. Considering diurnal and nocturnal mammals separately, we examine (1) the effects of fragmentation, and degradation on the habitat use and (2) the overlap in their diel activity across the different forest sizes. Habitat use by diurnal mammals increased with forest size, but not that of nocturnal species. In general, diurnal mammals anticipate their peak activity from 00:00 h to 6:00 h into smaller fragments (< 100 ha). The diel activity patterns of diurnal mammals in small (< 50 ha) and large (< 500 ha) fragments were diverged to those in continuous forest. On the other hand, the diel activity patterns of nocturnal mammals across all size categories showed high overlap with those in continuous forest, indicating that diel activity patterns remained constant along the forest-size gradient. Such behavioral responses of diurnal mammals may be due to changes in fragment size, which alter the temporal availability of trophic resources and, consequently, may increase interspecific competition for limited resources. These findings comprise baseline knowledge informing evidence-based mechanisms of mammalian adaptation in human-modified regions across the tropics.