TY - JOUR
T1 - Toughness of the Virunga mountain gorilla (Gorilla beringei beringei) diet across an altitudinal gradient
AU - Glowacka, Halszka
AU - Mcfarlin, Shannon C.
AU - Vogel, Erin R.
AU - Stoinski, Tara S.
AU - Ndagijimana, Felix
AU - Tuyisingize, Deo
AU - Mudakikwa, Antoine
AU - Schwartz, Gary
N1 - Funding Information:
We gratefully acknowledge the Rwandan government for their permission to work in Volcanoes National Park, and the many field researchers and staff of DFGFI's Karisoke Research Center for their commitment to the gorillas and tireless efforts to generate long-term data, without which this study would not be possible. DFGFI also gratefully acknowledges the public and private agencies, foundations, and individuals that have provided support for the Karisoke Research Center. Funding to HG was provided by an American Society of Primatologists Small Research Grant, an International Primatological Society Research Grant, an ASU School of Human Evolution and Social Change Graduate Student Research Grant, and an Institute of Human Origins Fellowship. Support to SCM was provided from NSF-BCS 0852866 and 0964944. The field tester kit was purchased with a National Science Foundation grant to ERV (BCS-0643122). We thank Veronica Vecellio of the Karisoke Research Center for discussions on mountain gorilla foods and help with planning and executing plant collection. Further, we thank Vivek V. Venkataraman for discussion on the project and comments on the manuscript, the Associate Editor and two anonymous reviewers for their constructive comments on the manuscript.
Publisher Copyright:
© 2017 Wiley Periodicals, Inc.
PY - 2017/8
Y1 - 2017/8
N2 - The robust masticatory system of mountain gorillas is thought to have evolved for the comminution of tough vegetation, yet, compared to other primates, the toughness of the mountain gorilla diet is unremarkable. This may be a result of low plant toughness in the mountain gorilla environment or of mountain gorillas feeding selectively on low-toughness foods. The goal of this paper is to determine how the toughness of the mountain gorilla diet varies across their habitat, which spans a large altitudinal range, and whether there is a relationship between toughness and food selection by mountain gorillas. We collected data on the following variables to determine whether, and if so how, they change with altitude: leaf toughness of two plant species consumed by mountain gorillas, at every 100 m increase in altitude (2,600–3,700 m); toughness of consumed foods comprising over 85% of the gorilla diet across five vegetation zones; and toughness of unconsumed/infrequently consumed plant parts of those foods. Although leaf toughness increased with altitude, the toughness of the gorilla diet remained similar. There was a negative relationship between toughness and consumption frequency, and toughness was a better predictor of consumption frequency than plant frequency, biomass, and density. Consumed plant parts were less tough than unconsumed/infrequently consumed parts and toughness of the latter increased with altitude. Although it is unclear whether gorillas select food based on toughness or use toughness as a sensory cue to impart other plant properties (e.g., macronutrients, chemicals), our results that gorillas maintain a consistent low-toughness dietary profile across altitude, despite toughness increasing with altitude, suggest that the robust gorilla masticatory apparatus evolved for repetitive mastication of foods that are not high in toughness.
AB - The robust masticatory system of mountain gorillas is thought to have evolved for the comminution of tough vegetation, yet, compared to other primates, the toughness of the mountain gorilla diet is unremarkable. This may be a result of low plant toughness in the mountain gorilla environment or of mountain gorillas feeding selectively on low-toughness foods. The goal of this paper is to determine how the toughness of the mountain gorilla diet varies across their habitat, which spans a large altitudinal range, and whether there is a relationship between toughness and food selection by mountain gorillas. We collected data on the following variables to determine whether, and if so how, they change with altitude: leaf toughness of two plant species consumed by mountain gorillas, at every 100 m increase in altitude (2,600–3,700 m); toughness of consumed foods comprising over 85% of the gorilla diet across five vegetation zones; and toughness of unconsumed/infrequently consumed plant parts of those foods. Although leaf toughness increased with altitude, the toughness of the gorilla diet remained similar. There was a negative relationship between toughness and consumption frequency, and toughness was a better predictor of consumption frequency than plant frequency, biomass, and density. Consumed plant parts were less tough than unconsumed/infrequently consumed parts and toughness of the latter increased with altitude. Although it is unclear whether gorillas select food based on toughness or use toughness as a sensory cue to impart other plant properties (e.g., macronutrients, chemicals), our results that gorillas maintain a consistent low-toughness dietary profile across altitude, despite toughness increasing with altitude, suggest that the robust gorilla masticatory apparatus evolved for repetitive mastication of foods that are not high in toughness.
KW - dietary ecology
KW - food material properties
KW - masticatory morphology
KW - mountain gorilla
KW - toughness
UR - http://www.scopus.com/inward/record.url?scp=85017473548&partnerID=8YFLogxK
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U2 - 10.1002/ajp.22661
DO - 10.1002/ajp.22661
M3 - Article
C2 - 28388822
AN - SCOPUS:85017473548
SN - 0275-2565
VL - 79
JO - American Journal of Primatology
JF - American Journal of Primatology
IS - 8
M1 - e22661
ER -