Levy walk patterns in the foraging movements of spider monkeys (Ateles geoffroyi)

TL;DR

This study reveals that spider monkeys' foraging movements exhibit Levy walk patterns characterized by power-law distributions in step lengths and waiting times, aligning with optimal search strategies for scarce resources.

Contribution

The paper demonstrates that spider monkeys' foraging trajectories follow Levy walk patterns, providing insights into their search strategies and ecological behavior.

Findings

Step lengths follow a power-law distribution close to theoretical Levy walk predictions.

Waiting times between movements also follow a power-law distribution.

Mean square displacement indicates Levy walk-like movement patterns.

Abstract

Scale invariant patterns have been found in different biological systems, in many cases resembling what physicists have found in other nonbiological systems. Here we describe the foraging patterns of free-ranging spider monkeys (Ateles geoffroyi) in the forest of the Yucatan Peninsula, Mexico and find that these patterns resemble what physicists know as Levy walks. First, the length of a trajectory s constituent steps, or continuous moves in the same direction, is best described by a power-law distribution in which the frequency of ever larger steps decreases as a negative power function of their length. The rate of this decrease is very close to that predicted by a previous analytical Levy walk model to be an optimal strategy to search for scarce resources distributed at random Viswanathan et al 1999). Second, the frequency distribution of the duration of stops or waiting times also approximates a power-law function. Finally, the mean square displacement during the monkeys first foraging trip increases more rapidly than would be expected from a random walk with constant step length, but within the range predicted for Levy walks. In view of these results, we analyze the different exponents characterizing the trajectories described by females and males, and by monkeys on their own or when part of a subgroup. We discuss the origin of these patterns and their implications for the foraging ecology of spider monkeys.