More on the meanderings of mangabeys: how to test whether bounded walks are random

1. Barrett & Lowen (1998) and Waser (1976) attempted to explain the net mon thly and yearly displacements of Grey-Cheeked Mangabeys using observed shor t-term step lengths and assuming a random walk, with and without boundaries . This paper reanalyses their data. 2. Analytic approaches require the root-mean-square step length, not the me an. However, a more flexible approach to making and testing predictions is Monte-Carlo simulation. With a random walk long-term displacements have a l arge variance, so a single observation is unlikely to disprove this null hy pothesis. 3. Restricting movement to a square lattice is a reasonable approximation e ven when rectangular boundaries are incorporated. Describing the boundary c onfiguration accurately is more important. 4. The observed non-uniformity in turning angles should have been incorpora ted as it has a large effect on predicted net displacements, unless the are na is tightly constricted. Randomness of movement within a day can be disti nguished from that between days. For Waser's population it makes sense to p redict long-term displacements using only long-distance daily displacements . 5. There are better approaches to establish both whether boundaries exist a nd whether movements follow a random walk.