Territory size and defendability in primates

Mitani and Rodman (1979) showed that a simple measure of the defendability of the range area could differentiate fairly successfully between territorial and non-territorial species of primates. Their analysis has, however, been much criticised on the grounds that it considered only the day journey length and the diameter of the range area. We develop a number of more realistic indices of territory defendability that take into account both the length of the boundary to be defended and the detection distance as well as linear measures of range size. These indices (a) discriminate between territorial and non-territorial species more successfully than the Mitani-Rodman index and (b) allow the results to be extended to species which do not forage in cohesive groups. However, our results suggest that the Mitani-Rodman analysis was in many ways correct. © 1994 Springer-Verlag.