| We surveyed that feeding damage by nutria (Myocastor coypus) to unionid mussels in a floodplain water-body of the Kiso River, Japan. We analyzed 8 shell mounds composed of a total of 357 shells including Anodonta spp. (1.1％), Unio douglasiae nipponensis (22.7％), and Lanceolaria grayana (76.2％). Our results of Manly's α (significant level was above α=0.33) revealed that Lanceolaria grayana was strongly selected by feeding nutria (α=0.90) with neither Anodonta spp. (α=0.02) nor U. d. nipponensis (α=0.07) being selected. In addition, we confirmed tooth marks (i.e.scratches and cracks) on 78.7％ of these shells: only scratches on U.d. nipponensis, whereas both types of marks on Anodonta spp. and L. grayana. These findings suggest that unionid mussels were available food resource for the nutria, and that the food availability for the nutria was differed between mussel species. |
