Seed dispersal of muskoxen (Ovibos moschatus) and semi- domesticated reindeer (Rangifer tarandus tarandus), in Sweden

Seed dispersal plays a crucial role in shaping plant community composition, especially in the face of habitat loss, where arctic habitats are particularly vulnerable to climate change. Large herbivores such as muskoxen (Ovibos moschatus) and reindeer (Rangifer tarandus tarandus) may contribute to seed dispersal through endozoochory in arctic habitats. These species are mobile and have long digestive retention times, which could enable long-distance dispersal. This study investigates the vascular plant composition in a bare mountain region in Härjedalen, Sweden, where wild muskoxen roam in summer, and examines what seeds muskoxen and reindeer disperse through their dung. Feces samples were collected in the wild from reindeer and muskoxen. Feces were also gathered from captive muskoxen at the Muskox Centre in Härjedalen during late winter and the summer of 2024. Vegetation inventories were conducted within 10 x 10-meter plots placed around dung samples. A total of 33 vascular plant species were identified in the area. The plant species composition in reindeer and muskox plots differed despite an overlap in plant species. There was a tendency for a higher species richness around muskox droppings than around reindeer droppings. Wild muskoxen and reindeer dispersed relatively few seeds in total (four for reindeer and 11 for wild muskoxen) and species in total (three for reindeer and five for wild muskoxen) through their dung and likely have limited roles as endozoochorous dispersers in the study area. However, captive muskoxen dispersed significantly more seeds than wild muskoxen and reindeer, indicating their potential as seed dispersers below the tree line, especially as wild muskoxen moved below the tree line in late summer. Further research is needed to fully understand the contributions of these large herbivores to plant community dynamics in Swedish arctic habitats.