Vulnerability of Acorn Weevils (Coleoptera: Curculionidae) and Attractiveness of Weevils and Infested Quercus alba Acorns to Peromyscus leucopus and Blarina brevicauda

Both Peromyscus leucopus white-footed mice and Blarina brevicauda shorttailed shrews prey upon the curculionid weevils that attack Quercus alba acorns. Peromyscus leucopus also feeds on Q. alba acorns, but B. brevicauda does not. We conducted feeding experiments using weevil larvae or pupae (1) to determine the relative preference of P leucopus for infested and noninfested acorns; (2) to examine consumption rates of P leucopus and B. brevicauda when larvae are freely available, and (3) to determine whether weevils that have exited acorns and burrowed into the soil are differentially vulnerable to these two predators. No preference by P leucopus was detected in either field or laboratory studies where entire acorns were offered, but P leucopus showed a significant preference for sound over infested when only nutmeat was presented. No significant changes in the rate of consumption of larvae were detected over a 3-day trial period, nor did consumption rate change as the number of exposed larvae was increased from 30 to 50. Curculio pardalis (89 %) and Conotrachelus naso (6%) were the most prevalent weevil species encountered. Overwintering weevils burrowed up to 21 cm into the soil. Blarina brevicauda preyed upon pupae at depths to 15 cm, but P leucopus foraged efficiently to only 3 cm. The null hypothesis that the ratio of sound to infested acorns has no affect on acorn mortality due to granivory by P leucopus could not be rejected on the basis of field experiments using exclosures. Although neither species clearly regulates weevil abundance, B. brevicauda seems a likely determinant of adult weevil abundance in years following low acorn production.