TERRITORIALITY - RELATION OF RANGING PATTERN AND HOME RANGE SIZE TO DEFENDABILITY, WITH AN ANALYSIS OF TERRITORIALITY AMONG PRIMATE SPECIES

1. Existing theory suggests that territoriality will evolve when resources are limited and defendable, but defendability has seldom been analyzed quantitatively. 2. Here we argue that defendability depends on the ability of an animal to monitor the boundaries of its range in order to detect potential intruders and introduce an index of defendability (D) which is the ratio of observed daily path length (d) to an area equal to the diameter (d′) of a circle with area equal to home range area of the animal. This index is sensitive only to extreme deviation from circular shape. 3. Review of the literature on primate ranging reveals that all territorial groups for which data are available have an index of 1.0 or greater, and that few nonterritorial species have an index of 1.0 or greater. 4. Regression analysis of the relationship of daily path length to feeding group weight and foliage in the diet reveals that both feeding group weight and foliage in the diet account for a large proportion of the variance in daily path length, and that territorial and nonterritorial groups do not differ in day range for a given group weight and diet. © 1979 Springer-Verlag.