Competition for acorns among wild boar (Sus scrofa) and small mammals in aMediterranean woodland

Observations of the rooting activity of wild boar in a holly-oak grove show ed that in March-April the decrease of scorns in the diet (31%) was lower t han their availability (82%). Moreover the occurrence of deep rooting event s remains high despite the low occurrence of grass roots in the diet. These observations suggested that wild boar may exploit hoards of acorns collect ed by small mammals living in the study area (mainly wood mice Apodemus sp. ). in order to test this hypothesis two experimental trials were set up to: (1) investigate whether wild boar were able to locate acorns buried in the ground (range 0-30 cm) and (2) establish if mouse burrows were more likely to be excavated than locations without burrows. The results clearly show t hat wild boar actively search for buried acorns, mainly in March (59% vs 31 % in April and nothing in May) and that burrows are excavated significantly more than locations without burrows (ratio 2:1, respectively). Moreover, l ocations with burrows are characterized by a decline of rooting activity as a function of the distance from their centre (P = 0.02), which is absent i n the control locations (P = 0.74). Our results show that wild boar are abl e to partly compensate for a reduced above-ground availability of scorns by predating on hoards collected by small mammals. Since this occurs during a critical period for female wild boar when they are giving birth and lactat ing, this behaviour may strongly influence the population dynamics of both wild boar and small mammals.