Reindeer ( Rangifer tarandus ), a keystone species of Arctic and subarctic ecosystems, display remarkable ecological and behavioural plasticity, occupying environments ranging from open tundra to closed taiga forests. However, little is known about dietary variability among wild forest reindeer ( R.t. fennicus ) or semi-domesticated populations ( R.t. tarandus ) inhabiting similar forested landscapes. This study investigates t...