FACTORS AFFECTING SIZES OF HOME RANGE AND TERRITORY IN PIKAS

Abstract

The purposes of the present study are to examine the validity of two methods for measurement of home range and to reveal factors affecting sizes of home range and territory on the basis of direct observation of the pika (Ochotona princeps, Lagomorpha). Home range size was estimated by two methods : 1) Home ranges outlined by connecting the outermost periphery of moving routes were calculated with a planimeter. 2) A home range map was superimposed on a 5-m grid system, and home range size was obtained by counting the number of utilized squares. Home range size calculated only by the second method was apparently overestimated. Home range size was affected by sex, age, dominance rank and the size of rock slides. Home range size was smaller and population density was higher in small rock slides than in a large rock slide. Due to occasional invasions of males into other territories, the mean percentage of territories to home ranges was much lower in male than in female, and the home range size often increased after the observation area curve had attained the plateau. The results of the present study strongly suggest that live-trapping procedures are inadequate for making realistic estimates of home ranges.