Human pressure and protection gradients reshape diel activity patterns of terrestrial mammals.

Abstract

Background: Human activities increasingly reshape wildlife diel activity patterns, yet species-specific adjustments across land-use gradients with varying levels of human pressure and protection remain poorly understood. Nepal's 2020 COVID-19 lockdown created a quasi-experimental reduction in human mobility, allowing clearer attribution of temporal responses to human pressure.

Methods: Using camera trap data from matched 30-day windows (March 24-April 24) in 2019 (pre-lockdown) and 2020 (lockdown) across the Bardia complex, representing a mosaic of human pressure and protection gradients, including Bardia National Park (NP), its buffer zone (BZ), and adjacent human-dominated areas outside of buffer zone (OBZ). NP-2020 treated as the baseline and quantified species-specific activity patterns with kernel densities, coefficients of overlap (Δ, 95% CIs), circular mean peak-time shifts (hours, 95% CIs), and a nocturnality index (% detections between 19:00-05:00 h, 95% bootstrap CIs). We analyzed four contrasts and reported overlap and peak-time shifts within species, contrasting NP-2020 with the same species in BZ and OBZ during survey periods 2019 and 2020.

Results: Relative to the NP-2020, herbivores -especially chital, barking deer, hog deer, and wild boar shifted activity peaks by ~ 6-11 h toward night and showed reduced overlap within-species in BZ and OBZ, with several near anti-phase schedules in OBZ. Sambar remained comparatively stable and crepuscular, while tigers exhibited low NP-BZ overlap and near 12 h offsets in their activity peaks. Lockdown conditions increased overlap and attenuated nocturnal displacement for several species (notably chital and sambar), evidencing rapid behavioral relaxation.

Conclusion: The dominant pattern is a gradient of increasing nocturnality and declining overlap in activity patterns as human pressure increases from NP to BZ to OBZ, with persistent nocturnality in hog deer and wild boar indicating chronic constraints. We emphasize integrating temporal refugia into management by limiting high-intensity human activities during crepuscular periods and reducing nighttime noise and lighting at forest-agriculture interfaces, so wildlife need not rely on extreme nocturnality to coexist with humans. Long-term monitoring that couples activity metrics (overlap, peak-time shifts) with environmental factors and physiological indicators is needed to evaluate demographic and fitness consequences and to inform temporal ecology in multi-use landscapes.