, Volume 174, Issue 4, pp 1127–1137 | Cite as

Faecal particle size in free-ranging primates supports a ‘rumination’ strategy in the proboscis monkey (Nasalis larvatus)

  • Ikki MatsudaEmail author
  • Augustine Tuuga
  • Chie Hashimoto
  • Henry Bernard
  • Juichi Yamagiwa
  • Julia Fritz
  • Keiko Tsubokawa
  • Masato Yayota
  • Tadahiro Murai
  • Yuji Iwata
  • Marcus Clauss
Physiological ecology - Original research


In mammalian herbivores, faecal particle size indicates chewing efficiency. Proboscis monkeys (Nasalis larvatus) are foregut fermenters in which regurgitation and remastication (i.e. rumination) was observed in the wild, but not with the same consistency as found in ruminants and camelids. To test whether this species has exceptional chewing efficiency among primates, as ruminants have among mammals, we compared faecal particle size in free-ranging specimens with those of 12 other primate species. The discrete mean faecal particle size (dMEAN) increased with body mass (M) as dMEAN (mm) = 0.65 (95 % confidence interval 0.49–0.87) M 0.33 (0.23–0.43) in simple-stomached species. At 0.53 ± 0.09 mm, dMEAN of proboscis monkeys was particularly small for their average M (15 kg) and significantly smaller than values of two other foregut fermenting primate species. While we cannot exclude other reasons for the exceptional chewing efficiency in proboscis monkeys, this represents circumstantial evidence for regular use of rumination in this species. Thus, proboscis monkeys might be a model for convergent evolution towards rumination in a non-ungulate taxon.


Chewing efficiency Foregut fermentation Simple stomach Digestive efficiency Food toughness 



I. M. and T. M. thank the Economic Planning Unit of the Malaysian Government, the Sabah Wildlife Department staff, the Kinabatangan Orangutan Conservation Project and our research assistants for support. C. H. is grateful to the Uganda National Council for Science and Technology, the Uganda Forestry Department, and the Uganda Wildlife Authority for permission to work in the Kalinzu Forest. J. Y., K. T. and Y. I. thank the CENAREST, Gabon and the IRET, Gabon, the Ministere des Eaux et Foret and the Conseil Nationale des Parcs Nationaux of the Gabonese government. We thank T. Yamda and S. Higashi for arranging the video data of proboscis monkeys, K. Doi for the sieving of the faecal samples, and two anonymous reviewers for valuable comments. This study was financed by the HOPE and Human Evolution Project of KUPRI (to I. M. and C. H.); a JSPS Grant-in-Aid for challenging Exploratory Research (24657170 to I. M.) and Scientific Research (22255007 to T. Furuichi; 24255010 to J. Y.) by MEXT; a Sasakawa Scientific Research Grant from the Japan Science Society (to I. M.); the Environment Research and Technology Development Fund (D-1007 to T. F.); the JSPS Asia-Africa Science Platform Program (2009–2011 to T. F.); SATREPS by JST and JICA, Japan (to J. Y.). This study was conducted in compliance with animal care regulations applicable to Malaysian, Ugandan and Gabonese laws.


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Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Ikki Matsuda
    • 1
    Email author
  • Augustine Tuuga
    • 2
  • Chie Hashimoto
    • 1
  • Henry Bernard
    • 3
  • Juichi Yamagiwa
    • 4
  • Julia Fritz
    • 5
  • Keiko Tsubokawa
    • 4
  • Masato Yayota
    • 6
  • Tadahiro Murai
    • 7
  • Yuji Iwata
    • 8
  • Marcus Clauss
    • 5
  1. 1.Primate Research InstituteKyoto UniversityInuyamaJapan
  2. 2.Sabah Wildlife DepartmentKota KinabaluMalaysia
  3. 3.Institute for Tropical Biology and ConservationUniversiti Malaysia SabahKota KinabaluMalaysia
  4. 4.Graduate School of ScienceKyoto UniversityKyotoJapan
  5. 5.Clinic for Zoo Animals, Exotic Pets and Wildlife, Vetsuisse FacultyUniversity of ZurichZurichSwitzerland
  6. 6.Faculty of Applied Biological SciencesGifu UniversityGifuJapan
  7. 7.Foundation of Environmental Culture and Education, IncorporatedIidaJapan
  8. 8.Faculty of Children StudiesChubu-Gakuin UniversitySekiJapan

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