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1. Condensed tannins and nutritional quality of Bornean orangutan (Pongo pygmaeus wurmbii) foods in Gunung Palung National Park, West Kalimantan, Indonesia

   Chowdhury, Ishrat; Eori, Madeline; Kane, Erin E.; Conklin-Brittain, Nancy L.; Susanto, Tri Wahyu; Knott, Cheryl D. (February 2020, American journal of physical anthropology)

   Orangutan habitats are characterized by fluctuations in the availability of ripe fruits. During non-fruiting periods orangutans typically incorporate more lower-quality foods such as pith and bark in their diet. Condensed tannins (CT) are secondary plant compounds that bind to proteins, thus impeding the digestibility of proteins, and tending to make foods bitter or unpalatable. We analyzed condensed tannin content in 129 plant samples collected from Gunung Palung National Park in Borneo, Indonesia between 1994 and 2001. We predicted that CT concentrations would be highest in bark, and that there would be a correlation between protein and condensed tannin content. We used ANOVA with Bonferonni’s method for post-hoc comparisons to test for differences in tannin content between plant parts, and Pearson’s correlation to test for relationships between tannin concentrations and other nutrients. There were significant differences in condensed tannin content (F(4)=2.70, p=0.03) but no differences after adjusting the alpha-level for post-hoc comparisons. Whole fruit (including the skin) tended to have the highest CT concentration. However, we found no correlation between CT and concentration of nutrients including crude protein (R=0.12, p=0.19, N=127), free simple sugars (R=-0.09, p=0.40, N=100), or fiber (R=-0.38, p=0.67, N=128). This underscores that plants rich in desirable nutrients may also be rich in antifeedants, posing challenges for orangutan consumption and digestion even as they provide a source of high-quality energy. Additionally, for some food categories where high tannin content is predicted, such as bark, orangutans may be choosing to eat species that are lower in these compounds. 

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2. Dietary fiber and nutritional quality of the foods of Bornean orangutans (Pongo pygmaeus wurmbii) in Gunung Palung National Park, West Kalimantan, Indonesia

   Chowdhury, Ishrat; Eori, Madeline; Susanto, Tri W; Kane, Erin; Conklin-Brittain, Nancy L; Knott, Cheryl D (March 2019, American journal of physical anthropology)

   Wild Bornean orangutans experience fluctuations in the availability of their preferred food, fruit. During periods of low fruit availability, orangutans rely on fallback foods which are expected to be higher in fiber and generally lower in free simple sugars. However, it is not clear whether there is a consistent relationship between fiber content and the content of other nutrients. Here, we examine acid detergent fiber (ADF) content of 101 plant foods consumed by orangutans in Gunung Palung National Park, West Kalimantan, Indonesia, and the correlation between ADF and other important plant macronutrients. Samples were collected during full-day behavioral follows between 1994-2001. Samples were analyzed in triplicate through a reflux apparatus, which quantified ADF proportion by weight. An ANOVA revealed significant differences between ADF concentrations of different plant parts (F(5)=20.89, p < 0.001). Post-hoc analyses (α= 0.005) determined that bark had a significantly higher ADF concentration than pulp and seeds (p<0.001), leaves had a significantly higher ADF concentration than seeds (p<0.001), and whole fruit had a significantly higher ADF concentration than pulp or seeds (p<0.001). We found a negative correlation between free simple sugar concentration and ADF (R = -0.63, p<0.001). However, there was no significant correlation between ADF and protein (R=-0.14, p=0.17) or lipid (R 0.134, p=0.19) content. Our findings corroborate work showing that bark and leaves are particularly high in ADF. However, they underscore the fact that determining dietary quality is complex, and that food items that are high in fiber may still be good sources of non-carbohydrate energy. National Science Foundation (BCS-1638823, BCS-0936199, 1540360, 9414388); National Geographic Society; US Fish and Wildlife (F15AP00812, F12AP00369, 98210-8-G661); Leakey Foundation; Disney Wildlife Conservation Fund; Wenner-Gren Foundation; Nacey-Maggioncalda Foundation; Conservation, Food and Health 

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3. Quantifying free simple sugars in orangutan foods using spectrophotometry: Implications for orangutan feeding ecology

   Robinson, Natalie; Lang, Lexi; Kane, Erin; Knott, Cheryl (April 2018, 87th Annual Meeting of the American Association of Physical Anthropologists)

   Orangutans (Pongo pygmaeus wurmbii) in Gunung Palung National Park, West Kalimantan, Indonesia experience significant seasonal and annual fluctuations in the availability of their preferred food, ripe fruit. When ripe fruit is limited, orangutans increase their consumption of bark, pith, and leaves, which are continuously available and may act as fallback foods. While these foods are presumed to be less nutritious, it is not clear whether this is the case. Free simple sugars (FSS) provide orangutans with readily-metabolizable energy, and are thus an important nutritional compound for food choice. Here, we examine FSS concentrations in a variety of orangutan foods (n=54) to better understand orangutan foraging and nutritional ecology. We predicted that preferred foods would have higher concentrations of FSS than fallback foods. We analyzed FSS concentrations using a modified phenol-sulfuric acid method, and tested sample absorbency using a spectrophotometer at 490 nm. We analyzed 54 samples from 48 species, examining six plant parts: bark, flowers, leaves, pulp, seeds, and skin/pulp. Although preliminary results indicated no statistically significant differences in sugar content across the six food categories (F(5,47)=1.78, p=0.14), we did find that preferred foods (fruit pulp and seeds) had an average sugar concentration that was significantly higher (4.7%) than fallback foods (leaves and bark) (t=2.355, p=0.04). Therefore, as predicted, we find that orangutans prefer food types with higher concentrations of FSS. Obtaining adequate caloric and nutritional intake is crucial for orangutan reproduction and development, and thus this study provides new insight into what drives orangutan dietary choices. National Science Foundation (BCS-1638823, BCS-0936199, 9414388), National Geographic Society, US Fish and Wildlife (F15AP00812, F12AP00369, 98210-8-G661), Leakey Foundation, Disney Wildlife Conservation Fund, Wenner-Gren Foundation, Nacey- Maggioncalda Foundation. 

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4. Home Range Overlap in Female Bornean Orangutans: Responses to Fluctuations in Food Availability

   Zdanowicz, V; Blackburn, A; Susanto, TW; Knott, CD (January 2020, 6th Annual Meeting of the Northeastern Evolutionary Primatologists)

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   Bornean orangutans (Pongo pygmaeus wurmbii) are large bodied great apes that live in rainforests dominated by mast-fruiting dipterocarp trees with extreme fluctuations in fruit availability. Orangutans respond to this temporal and spatial variability in fruit production by ranging over large areas and adopting a semi-solitary social structure. Females have overlapping home ranges, engage in both scramble and contest competition for food, and actively avoid each other. Overlap requires individuals to share access to resources and adjust ranging to optimize energy intake, thus habitat quality likely influences ranging patterns. Here we investigate whether habitat and food availability are significant predictors of female orangutan home range overlap using data collected at Gunung Palung National Park, Indonesia, a site with 7 distinct habitats. Researchers collected GPS waypoints of orangutan movements during all day focal follows. Fruit availability was measured through monthly monitoring of over 6000 trees, across 60 plots. We used R to calculate range overlap per habitat between pairs of adult female orangutans over three-month periods (2013-2019). Our results show a trend towards a negative relationship between overlap and fruit availability (N=15, Pearson’s R= -0.322, p=0.242). We also found habitat to be a predictor of female range overlap, with overlap most likely to occur in the alluvial bench habitat and significantly less likely in the peat swamp (p<0.05). These findings reveal the independent influences of fruit availability and habitat type on female orangutan home range overlap, highlighting the potential importance of habitat-specific food availability on ranging behavior and contest competition. Funders: NSF (9414388, BCS-1638823, BCS-0936199); National Geographic; USFish/Wildlife (F18AP00898, F15AP00812, F13AP00920, 96200-0-G249, 96200-9-G110); Leakey; Disney Conservation Fund; Wenner-Gren; Nacey-Maggioncalda; Conservation-Food-Health; Orangutan Conservancy; Woodland Park Zoo; Boston University GRAF 

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5. Ingestive Behavior of Bornean Orangutans (Pongo pygmaeus wurmbii): coping with mechanical challenges while foraging

   Kane, Erin; McGraw, Scott; Laman, Tim; Susanto, Tri Wahyu; Knott, Cheryl (April 2018, 87th Annual Meeting of the American Association of Physical Anthropologists)

   Bornean orangutans (Pongo pygmaeus wurmbii) preferentially eat pulp and mesocarp when fleshy fruit is abundant. However, during non-masting periods, orangutans rely on foods that can be mechanically challenging, including leaves, woody plant tissue, and seeds. Although adult orangutans’ jaws are well adapted for intense and, perhaps, repetitive loading during chewing, it may be easier for flanged adult males to process tough or hard foods than for adult females because of dramatic sexual dimorphism. Here, we use video data and in situ focalobservations from Gunung Palung National Park, West Kalimantan, Indonesia to test the hypotheses that orangutans exhibit food- and sex-specific oral processing profiles. Pilot data (n=94 feeding bouts; 76 adult females, 18 adult males) suggest no significant differences in use of incisors (F(3,71)=0.41, p=0.75), canines (F(3,71)=0.78, p=0.52), or molars (F(3,71)=0.88, p=0.46) per ingestive action while processing fruit, leaves, termites, or bark. Females used significantly more incisions per ingestive action (2.20) than males (1.01) (t=2.44, p=0.008), and, though differences were not significant, performed more canine bites (female mean=0.08, male mean=0.00, p=0.17) and mastications (female mean=4.88, male mean=3.95, p=0.24) per ingestive action than males. We detected no difference in the behaviors used by orangutans to process different food types, despite great variation in food mechanical properties. However, this may be because our pilot data did not capture the range of mechanical challenges in orangutan diets. Nevertheless, our preliminary results support the hypothesis that adult females work harder than flanged males during oral food processing, explicable due to sexual dimorphism. National Science Foundation (BCS-1638823, BCS-0936199); National Geographic Society; US Fish and Wildlife (F15AP00812, F12AP00369, 98210-8- G661); Leakey Foundation; Disney Wildlife Conservation Fund; Wenner-Gren Foundation; Nacey-Maggioncalda Foundation 

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