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Living in small spaces: Forest fragment characterization and its use by Philippine tarsiers (Tarsius syrichta Linnaeus, 1758) in Mindanao Island, Philippines


The Philippine tarsier (Tarsius syrichta) is a charismatic species that is threatened by illegal hunting and deforestation. Although they occur in forest and disturbed habitats, ecological information about them is still considerably lacking, which consequently hampers our ability to effectively protect tarsiers from further endangerment. Here, we characterized a 36-ha forest fragment in Mindanao Island where a population of tarsiers persist, and assessed the factors that could have influenced their distribution within the area. We sampled trees (> 1 cm DBH) within 10 × 10-m sampling plots (N = 54), which were established within 1-ha grids (N = 32) and locations where tarsiers were captured (N = 22). The habitat was characterized as a regenerating forest over limestone, with a generally homogeneous structure in terms of tree species richness, abundance, mean DBH, and height. In both sampling plots, we found an abundance of trees below 5 cm in DBH (> 50%) and between 2.6 and 5 m in height (> 40%), which, accordingly, the tarsiers appeared to prefer to use when foraging or sleeping. Lianas were among the most important features of the forest, possibly being a keystone structure in such habitats. Community assemblage, species richness, and mean height of trees, as well as distance to the forest edge, were found to be significant factors that influenced tarsier distribution in the fragment. Our study provides basic yet critical information on the habitat and ecology of Philippine tarsiers in Mindanao, and highlights the importance of forest fragments with rich flora diversity to the survival of the species.

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Fig. 1

Map source: Google Earth Satellite)

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(Map source: Google Earth Satellite). White squares represent 1-ha plot centers, and circles, in general, represent capture plots. Among capture plots, blue circles represent sleeping sites, and yellow circles represent foraging sites

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(Photographs by: Simeon Gabriel F. Bejar)


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This paper was part of an undergraduate thesis of SGFB. Funding was provided by Forest Foundation Philippines (formerly Philippine Tropical Forest Conservation Foundation), Holcim Philippines, Inc. (HPI), and Holcim Mining and Development Corporation (HMDC) through the Biodiversity Research Laboratory, Institute of Biology, College of Science, University of the Philippines Diliman and the Diliman Science Research Foundation. Thanks are due to the Department of Environment and Natural Resources Region 10 (DENR R10), the Protected Area Management Board (PAMB), former Protected Area Superintendent (PaSU) Liza Requina, PaSU Eddie Macasusi, and the rest of the staff for the logistic assistance and issuance of permits, and for allowing the authors to conduct the research in the Initao-Libertad Protected Landscape and Seascape under Gratuitous Permit no. R10-2014-36. The authors are grateful to Jaime Mangalindan, Nonito Antoque, Rey Antoque, and Medeva Jay Busaing for their assistance in the field, and to the biologists and research associates of the Biodiversity Research Laboratory, and Dr. Olga M. Nuneza and the volunteer student-researchers from Mindanao State University-Iligan Institute of Technology for their contributions in the data collection.

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The research project and study methods were conceptualized and designed by Perry S. Ong. Funding and managing of the research process were secured by Perry S. Ong, Mariano Roy M. Duya, and Melizar V. Duya. Data collection and fieldworks were conducted by Simeon Gabriel F. Bejar with John Michael M. Galindon. Data analyses were performed by Simeon Gabriel F. Bejar and Bonifacio O. Pasion. All authors were involved in the drafting and finalization of the manuscript.

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Correspondence to Simeon Gabriel F. Bejar.

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All applicable international, national, and/or institutional guidelines for the care and use of animals were followed. All animal procedures performed in this research were in accordance with the current laws of the Philippines as promulgated with the ethical standards under the Department of Environment and Natural Resources and the Protected Area Management Board, and approved under Gratuitous Permit no. R10-2014-36.

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Bejar, S.G.F., Duya, M.R.M., Duya, M.V. et al. Living in small spaces: Forest fragment characterization and its use by Philippine tarsiers (Tarsius syrichta Linnaeus, 1758) in Mindanao Island, Philippines. Primates 61, 529–542 (2020).

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  • Forest over limestone
  • Edge effect
  • Habitat use
  • Plant diversity
  • Substrate use
  • Tarsier ecology