Epizoochory by large herbivores: merging data with models

The dispersal of plant seeds in the fur of large herbivores (epizoochory) is an important but complex long-distance dispersal mechanism. We developed a spatially explicit simulation model of epizoochorous seed dispersal, which was parameterized based on empirical studies of the movement and behaviour of donkeys, and the distribution, seed production, seed accessibility, seed adhesion, and seed retention on donkey fur of selected plant species in a coastal dune nature reserve in Flanders, Belgium. We compared predicted and observed seed numbers of the 14 plant species on donkey fur.

Modelled seed shadows indicate that for most species about half of all seeds dispersed by donkeys should travel a net distance of >100 m, and about 1% should travel >500 m within this more or less isodiametric 100 ha nature reserve. Seeds with longer retention times are expected to travel further than those with short retention times. Enlarging the reserve area had little impact on the forecasted dispersal distances.

Variation among plant species in the observed seed numbers found on donkey fur were well predicted by the model (R²=0.56, P=0.002), though the predictions relied on relatively crude estimates of seed production and accessibility to donkeys, indicating that more accurate estimates of these parameters are needed.

Our model confirms the important role of epizoochory in affecting long-distance seed dispersal, and provides a modelling framework for integrating the multiple components of the dispersal process.