Phenological responses to climate change: advancing mating and calving in wild and semi‐captive Caspian red deer

Species respond to climate change through phenological and spatial shifts. Herbivorous mammals, in particular, are vulnerable due to their direct dependence on seasonal vegetation and the potential misalignment between their reproductive cycles and shifting food availability. This study examines the influence of temperature, rainfall, and humidity on the timing of mating and calving in wild and semi‐captive populations of Caspian red deer Cervus elaphus maral along the southern Caspian Sea. Our results reveal that in wild populations, rising temperatures from 1 September to 31 May led to earlier calving, while warmer conditions from 1 June to 31 August advanced mating. In contrast, no significant phenological shifts were observed in semi‐captive populations, likely due to supplemental feeding and environmental buffering. These findings suggest that climate‐induced reproductive changes may threaten the long‐term viability of the Caspian red deer, particularly as habitat fragmentation limits access to cooler, higher‐altitude refuges. Conservation efforts should prioritize habitat protection and connectivity in mountainous regions to support population resilience under ongoing climate change.