Daily activity pattern of mantled howlers (Alouatta palliata)

Activity patterns structure temporal niche partitioning across taxa, yet temporal organization of primate behavior remains poorly characterized relative to activity budgets. We investigated the daily activity pattern of mantled howlers (Alouatta palliata), energy-minimizing folivorous-frugivorous primates with characteristically high resting proportions. Between 2012 and 2021, we conducted 6828 h of focal observations on two groups in a forest fragment at Los Tuxtlas (México), assessing whether howlers exhibit structured temporal patterns and identifying factors influencing activity timing. Circular statistics revealed highly significant temporal structuring and cosinor analysis detected weakly unimodal patterns with substantial 12 h secondary periodicity. Wavelet analysis identified ultradian rhythms at 4 h intervals. Food abundance, temporal components, and group identity were highly influential in activity patterns, with food abundance negatively affecting activity, while temperature, rainfall, and reproductive state showed minimal effects. This study demonstrates that mantled howlers maintain structured unimodal activity patterns despite their energy-minimizing lifestyle, with resource availability and group identity exerting stronger influence on temporal organization than immediate climatic conditions.