Hitch-hiking in the wild: should seeds rely on ungulates?

Background – Seed dispersal appears to be a key process in maintaining plant population and community dynamics, even more so in the current context of global warming and landscape fragmentation. Wild ungulates, due to their capacity to cover long distances in a large variety of habitats, are potential vectors of long-distance dispersal for plants. Methods – In order to estimate their role as seed dispersal vectors, we conducted a cross-species comparative approach on three common wild ungulates: roe deer (Capreolus capreolus), red deer (Cervus elaphus) and wild boar (Sus scrofa). We brushed the fur and hooves of animals shot in Loiret forests during the hunting season and counted and identified the seeds transported on the animals' bodies. Results – We found seeds from 41 different plant species, 24% of which were found in the cleft of the hoof. Wild boar transported 85% of the species identified (versus 34% and 7% for roe and red deer respectively). More seeds from plants representing a greater variety of dispersal modes were carried by wild boar. Less than 50% of the transported plants were epizoochorous species. Moreover, the plants transported were mainly non forest or periforest light-demanding species. We also showed that wild boar is a vector for plants not specifically adapted to external dispersal, whereas red and roe deer are more prone to move epizoochorous species. Conclusion – Globally, our naturalist approach confirmed that common large ungulates are indeed effective vectors plants can rely on. Moreover, since many types of seeds are concerned, ungulates' specific role in plant dispersal should be reconsidered