Operationally Defining Home Range: Temporal Dependence Exhibited by Hispid Cotton Rats

Abstract

To determine whether cotton rats (Sigmodon hispidus) establish home ranges, and whether home—range size and shape vary temporally, we measured site fidelity at daily and multiday intervals. The concept of site fidelity can be used to provide a quantitative measure of the existence of a home range. Mean squared distance from the center of activity (MSD) and a linearity index (LI) were used to measure site fidelity of the hispid cotton rat. Significant differences for these metrics between actual and simulated, random movement showed that home ranges existed for both daily and multiday periods. Home—range characteristics varied with temporal scale. Daily home ranges were more concentrated (lower MSD), linear (higher LI), and elongate (higher eccentricity, ECC) than multiday home ranges. The effects of sex, age, and season on MSD, LI, and ECC differed for daily and multiday home ranges. The area of daily home range was not different between sexes or ages, or among seasons, but multiday home ranges was larger for males, for adults, and in winter and summer. Knowing that home ranges exist is a necessary prerequisite for ecology or behavioral interpretation of space—use patterns before comparisons of home—range characteristics are made, however, the temporal scale of measurement must be considered, because scale alone can yield differences in size and shape.