Range Use Patterns and Spatial Relationships of Merriam's Kangaroo Rats (Dipodomys Merriami)

Abstract

Radiotelemetry was used to investigate the home range patterns and inter-individual spatial relationships of Merriam's kangaroo rat (Dipodomys merriami). Sixty adult D. merriami (32 males and 28 females) were radio-tracked for varying lengths of time over three study periods between November 1980 and December 1982, on two desert habitat sites located near Palm Desert, California. Analyses of home range size and utilization patterns, range overlap with conspecifics, and day burrow distribution and use patterns were carried out. Home range varied between 0.03 ha and 1.16 ha with substantial inter-study differences but no apparent sex differences. Animals maintained relatively stable core activity loci within their ranges which were centered around frequently occupied day burrows. However, long sallies of 100 m or more away from core areas were not uncommon. The examination of shifts in animals' centers-of-activity (COA) over long periods of time indicated that animals maintained relatively stable home ranges over seasons and even years although a few individuals did exhibit COA shifts of more than 100 m. There was substantial home range overlap, with individuals overlapping the ranges of up to 14 radio-implanted conspecifics. The home ranges of pairs of neighboring females overlapped less than did those of males or pairs of opposite sex, and the average nearest-neighbor distance between the day burrows of males and females was significantly smaller than the average nearest-neighbor distance between females. Thus in kangaroo rats, as in other solitary rodents, females maintain territorial spacing to a greater degree than do males. D. merriami utilized several day burrows with moves occurring once every four days on average. However, most animals used only one or two day burrows frequently. The largest moves coincided with reproductive activity, and in particular with the day of estrus. The findings are discussed with respect to their implications for D. merriami social structure, and for comparative studies within the genus Dipodomys and within the order Rodentia.