Vol. 51 No. 7, 2012

Spatial Overlap between the Intermediate Egret Egretta intermedia and Its Aquatic Prey at Two Spatiotemporal Scales in a Rice Paddy Landscape

Naoki Katayama^1,*, Tatsuya Amano², Go Fujita¹, and Hiroyoshi Higuchi¹

¹Laboratory of Biodiversity Science, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
²Biodiversity Division, National Institute for Agro-Environmental Sciences, 3-1-3 Kannondai, Tsukuba-shi, Ibaraki 305-8604, Japan

Naoki Katayama, Tatsuya Amano, Go Fujita, and Hiroyoshi Higuchi (2012) Quantification of patterns of spatial overlap between predators and prey at multiple spatiotemporal scales can be a useful approach to understanding hierarchical predator-prey interactions.  To date, many empirical studies have focused on only fine spatial scales (less than a few hectares) except in pelagic marine systems.  Furthermore, the temporal scale of predator-prey overlap has rarely been explored.  This study investigated spatial overlaps between the Intermediate Egret Egretta intermedia and its aquatic prey at 2 scales in a rice paddy landscape in central Japan.  At a broad spatial scale (more than several hectares), both the egrets and their prey tended to be more abundant in the area of rice fields using traditional irrigation practices than in the area of fields using modern practices, during the flooding periods from late May to late June.  At a finer scale, there was a positive spatial correlation between abundances of egrets and their prey in each rice field only at the short temporal scale of a few days.  These results suggest that hierarchical predator-prey interactions in rice paddy landscapes are caused by several processes operating at different spatiotemporal scales.

Key words: Agricultural intensification, Foraging ecology, Multi-scale patch selection, Predator-prey interaction, Spatial distribution.

*Correspondence: Tel: 81-3-58417543.  Fax: 81-3-58417542.  E-mail:katayama@es.a.u-tokyo.ac.jp