Hairy prairie-clover (Dalea villosa var. villosa) is a rare plant species found in the Canadian Prairies that is believed to be vulnerable to extirpation. A significant threat to the Dundurn population in south-central Saskatchewan is intensive grazing by domestic livestock and wildlife, which reduces the survival, fitness, and productivity of D. villosa. Major herbivores in this area are cattle (Bos taurus), white-tailed deer (Odocoileus virginianus), and mule deer (Odocoileus hemionus). Preference or selectivity of cattle and deer for D. villosa has not been formally studied, and it is not known whether cattle or deer are responsible for the highest rate of herbivory. Several ecological and management-related factors may influence the probability of D. villosa patches and individual plants being grazed, and the extent to which they are grazed. These factors include cattle stocking rates, densities and times, proximity to preferred deer habitat, surrounding vegetation types, D. villosa patch size, shape, and density, and plant size.
Results/Conclusions
We conducted an observational study and used structural equation modeling to elucidate which factors are most influential on the herbivory of D. villosa. We found that some factors were directly influential, but that complex relationships among these factors determined the susceptibility of D. villosa plants and patches to herbivory from either cattle or deer. Identifying influential factors and their relationships is crucial to understanding the ecology and management implications of D. villosa populations where grazing may present an additional risk to the population. Furthermore, the findings and methodologies presented will be of value in the conservation of other rare species and populations.