Study finds previously unreported height use and increased social behavior in Philippine tarsiers, suggesting behavioral flexibility in fragmented habitats

08 Jan 2026

Sleep and sleep-related behaviors are integral components of primate behavior and ecology, linked to various habitat-specific factors and often modified in response to environmental fluctuations and threats.

Despite the growing literature on primates, information on sleep-related behaviors of tarsiers remains sparse, especially for Philippine tarsiers, where our current understanding is hampered by the paucity of studies on wild populations. We radio-tracked eight Philippine tarsiers inhabiting a protected forest fragment between December 2016 and February 2018 to assess their sleeping site selection, sleep-related positional behavior, and social system.

From 266 instantaneous sampling bouts, where each tarsier was observed a maximum of once per day, we found that the tarsiers frequently used trees with thickets of lianas and at least 15 plant species as sleeping sites. They slept from ground level to above 8 m, with most sightings at 3 to 6 m, and recurrent detections above 8 m, and preferred a flexed resting posture, on angled or horizontal, small-sized lianas or branches. Although frequently solitary, they also slept in pairs and in small groups of up to four individuals. We inferred polygyny based on observations of one adult male who associated and huddled with two non-associated adult females, and direct male care through huddling and accompaniment.

Our study revealed increased height use and gregariousness not previously described for Philippine tarsiers, shedding light on potential flexible behaviors by nocturnal primates in fragmented landscapes. Sleep-related behaviors present another avenue of research that has important implications for their conservation.

The data and analysis from this paper will greatly contribute to furthering the taxonomic study of the Philippine tarsier. This also gave us more information to understand the ecology and behavior of tarsiers.

Authors: Simeon Gabriel F. Bejar (Institute of Biology, University of the Philippines Diliman), Danah Marie P. Purificacion (Philippine Science High School Main Campus, Quezon City), Lemnuel V. Aragones (Institute of Environmental Science and Meteorology, University of the Philippines Diliman), Marilyn M. Balais (Institute of Environmental Science and Meteorology, University of the Philippines Diliman), Anna Pauline O. de Guia (Institute of Biological Sciences, College of Arts and Sciences, University of the Philippines Los Baños), Melizar V. Duya (Institute of Biology, University of the Philippines Diliman), Perry S. Ong (Institute of Biology, University of the Philippines Diliman) and Mariano Roy M. Duya (Institute of Biology, University of the Philippines Diliman)

Read the full paper: https://doi.org/10.1007/s10764-024-00443-5

Study finds previously unreported height use and increased social behavior in Philippine tarsiers, suggesting behavioral flexibility in fragmented habitats

Sleep and sleep-related behaviors are integral components of primate behavior and ecology, linked to various habitat-specific factors and often modified in response to environmental fluctuations and threats.

Despite the growing literature on primates, information on sleep-related behaviors of tarsiers remains sparse, especially for Philippine tarsiers, where our current understanding is hampered by the paucity of studies on wild populations. We radio-tracked eight Philippine tarsiers inhabiting a protected forest fragment between December 2016 and February 2018 to assess their sleeping site selection, sleep-related positional behavior, and social system.

From 266 instantaneous sampling bouts, where each tarsier was observed a maximum of once per day, we found that the tarsiers frequently used trees with thickets of lianas and at least 15 plant species as sleeping sites. They slept from ground level to above 8 m, with most sightings at 3 to 6 m, and recurrent detections above 8 m, and preferred a flexed resting posture, on angled or horizontal, small-sized lianas or branches. Although frequently solitary, they also slept in pairs and in small groups of up to four individuals. We inferred polygyny based on observations of one adult male who associated and huddled with two non-associated adult females, and direct male care through huddling and accompaniment.

Our study revealed increased height use and gregariousness not previously described for Philippine tarsiers, shedding light on potential flexible behaviors by nocturnal primates in fragmented landscapes. Sleep-related behaviors present another avenue of research that has important implications for their conservation.

The data and analysis from this paper will greatly contribute to furthering the taxonomic study of the Philippine tarsier. This also gave us more information to understand the ecology and behavior of tarsiers.

Authors: Simeon Gabriel F. Bejar (Institute of Biology, University of the Philippines Diliman), Danah Marie P. Purificacion (Philippine Science High School Main Campus, Quezon City), Lemnuel V. Aragones (Institute of Environmental Science and Meteorology, University of the Philippines Diliman), Marilyn M. Balais (Institute of Environmental Science and Meteorology, University of the Philippines Diliman), Anna Pauline O. de Guia (Institute of Biological Sciences, College of Arts and Sciences, University of the Philippines Los Baños), Melizar V. Duya (Institute of Biology, University of the Philippines Diliman), Perry S. Ong (Institute of Biology, University of the Philippines Diliman) and Mariano Roy M. Duya (Institute of Biology, University of the Philippines Diliman)

Read the full paper: https://doi.org/10.1007/s10764-024-00443-5