Dietary preference of European wild boar (Sus scrofa L.) grazing grass and legume at two contrasting plant heights: A pilot study

There were two objectives: checking a methodology to test diet preferences in a natural environment and secondly to assess diet preferences of European wild boar in terms of species and plant characteristics when offered in a situation with minimal physical constraints. Five hundred pots (100 mm upper diameter, 450 cc volume) were completely filled with soil. Half of the pots were sown with red clover (Trifolium pretense) and half with hybrid ryegrass (Lolium hybridum Hausskn). All pots were irrigated, periodically cut, and maintained outdoors. Then 220 leaves of ryegrass, 201 leaflets of clover and 188 petioles of clover were used to establish a relationship between plant structure dimensions and their dry matter mass. The preference study was conducted in a fenced area (18 m length and 11,1 m width) with a pasture cut to a height of 3 cm (lowest height possible to cover the soil). Four transects were marked separated 2 m from each other, and 16 holes within each transect were made 1 m apart, in which the pots were buried and anchored. Treatments consisted of the factorial combination of two plant species (red clover and hybrid ryegrass) and two plant heights (12 and 18 cm, tall and short, respectively), randomized within each transect (block). During three days, four nose-ringed wild boars grazed the experimental area for one hour and the treatments which they were grazing were recorded every two minutes. Plants structures were measured pre-and post-grazing from marked plants (green thread tied at the base) in each pot to detect consumption and to estimate the amount consumed. Strong correlations were found between plant structures and their dry mass (R2 between 0,83 and 0,89). The methodology was able to show that more dry matter was apparently consumed from clover than ryegrass (P<0.001) and clover had a greater probability of being grazed than ryegrass (P<0.05). Also, the tall plants were consumed more than the short plants (P<0.001) with individual tall plants having a higher probability of being grazed (P<0.05). It is concluded that the novel method proposed was able to detect the diet preferences of wild boar during grazing. Additionally, in this study European wild boar discriminated between plant species and between plant heights, preferring legume over ryegrass and taller over shorter plants. However, more studies with a greater number of animals are necessary to validate these results.