Rice plant damage distribution and home range distribution of the ricefield rat Rattus argentiventer (Rodentia : Muridae)

The patterns of rice plant damage distribution and the home distribution of the ricefield rat Rattus argentiventer were studied in a two hectare experimental field and in a two hectare enclosure. Damaged rice plants were randomly (Poisson) distributed during the vegetative stage of rice plant growth but tended to be aggregated or contiguous during the generative stage. Analysis of the spatial distribution of the rats' home ranges, using MORISITA's index of dispersion and nearest neighbor distances, indicated that (i) males showed a slightly stronger tendency to congregate than females, and (ii) females showed a uniform distribution pattern and had mutually exclusive home ranges from the birth season through the lactation period. Before and after the birth season, female rats had a random distribution pattern. Furthermore: an analysis of the degree of home-range overlap between the sexes found that male and female home ranges were distributed almost independently during the non-breeding and early mating seasons. However, early in the breeding season and at the end of the mating season, male and female home ranges overlapped completely. Male and female home ranges were completely exclusive from pregnancy until the end of lactation.