Predation by the carrion crow Corvus corone (Passeriformes: Corvidae) on the apple snail Pomacea canaliculata (Architaenioglossa: Ampullariidae) in different locations in Japan

Abstract

Alien species are exposed to novel species interactions in invaded ecosystems, and predators are important components of biotic resistance against aliens. The apple snail Pomacea canaliculata (Lamarck) (Architaenioglossa: Ampullariidae) was introduced to many countries, and causes severe problems including damage to young rice plants. Biotic resistance against the apple snail is generally weak in modernized rice fields, but carrion crows Corvus corone Linnaeus (Passeriformes: Corvidae) are observed to prey on apple snails. Thus, we investigated predation on the apple snails by the crows in three locations in Japan, and compared predation pressure, prey size, and predation methods among locations and different months/years in Ehime Prefecture. Carrion crows preyed on relatively small snails among subadults and adults in paddy fields. Predation rate within 1.2 m from the levee was as high as 87.1% in Ehime, 14.1% in Fukuoka (both in 2 days), and 1.1% in Nara (in 4 days). Thus, predation by crows is considered to be effective in reducing the density of snails in paddy fields in Ehime and possibly in Fukuoka. However, the period of predation and the intensity of predation varied from year to year in Ehime over a 3-year study period.