Behavioral plasticity and Lévy walk foraging strategies of red howler monkeys in a threatened montane forest

Montane forests (>1,000 m asl) present significant ecological challenges for arboreal foragers due to reduced primary productivity and the spatially aggregated, asynchronous distribution of fruit resources. To thrive in such environments, primates must employ adaptive movement strategies to optimize foraging efficiency. This study examines the behavioral plasticity of the red howler monkey ( Alouatta seniculus ) assessing whether the movement patterns are directed or random in response to fruit availability within a threatened high-Andean forest (2,500–3,000 m asl). We monitored two groups over an annual cycle, integrating spatial trajectory analysis with phenological data from 28 monitoring plots. Our results demonstrate that movement patterns align with "Lévy walks," characterized by clusters of short-step intensive searches interspersed with infrequent, long-distance directed displacements. High availability of fruits and flowers triggered a reduction in travel speed and daily distance, while simultaneously increasing step length and trajectory tortuosity—a hallmark of intensive patch exploitation. Conversely, higher leaf availability was associated with more linear, Brownian-like displacements. These responses varied between groups, revealing flexible spatiotemporal strategies for resource exploitation. These findings suggest that howler monkeys cognitively modulate their movement to maximize food encounter rates, reflecting a high degree of behavioral plasticity. Such adaptive movement strategies are essential for maintaining energetic balance in the face of habitat fragmentation and resource unpredictability. Our study provides evidence of how primates utilize complex searching strategies as a cognitive-driven mechanism to survive and adapt within rapidly changing and human-modified montane landscapes.