Abstract
<title>Abstract</title> <p> The extent to which upgrading protected areas contributes to wildlife population recovery remains a central question in conservation biology. We assessed population densities of large mammals following the 2019 gazettement of Ugalla River National Park in western Tanzania to evaluate whether enhanced protection status has initiated ecological recovery in a historically degraded ecosystem. Using ground-based line transect distance sampling, we estimated post-gazettement densities of large mammals and compared them with pre-gazettement baselines from the Ugalla River Game Reserve. Among eight species with historical comparisons, five showed increased densities. topi ( <italic>Damaliscus lunatus</italic> ) increased significantly (288%, p = 0.045), while defassa waterbuck, warthog, reedbuck, and lichtenstein's hartebeest showed substantial but non-significant increases. Impala, oribi, and giraffe showed non-significant declines. Elephant, buffalo, and carnivores were rarely detected, most likely reflecting life-history constraints and historical poaching legacies. Group size patterns further suggest early-stage population reorganization rather than complete ecosystem reassembly. Our findings demonstrate that gazettement can catalyze early wildlife recovery, but responses are species-specific and strongly constrained by historical disturbance and life-history traits. Sustained protection, habitat-focused management, and long-term monitoring will be essential to translate initial population gains into restored trophic structure and ecosystem function. </p>