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Orangutans are large-bodied frugivores predicted to be important seed dispersers, however little is known about their seed dispersal effectiveness. To understand wild Bornean orangutan (Pongo pygmaeus wurmbii) seed dispersal effectiveness, we measured the quantity of seeds dispersed, and we considered the quality of dispersal by measuring germination rates of gut-passed and control seeds, gut transit times, and dispersal distances. Research was conducted in Gunung Palung National Park, Borneo, Indonesia (August 2018 to August 2019). We systematically collected orangutan fecal samples, feeding behavior, and GPS tracks during consecutive full-day focal follows. We sieved 549 fecal samples collected from 36 orangutans to count and identify seeds (>2mm). Out of the fecal samples collected, 413 (75.2%) contained seeds. A total of 24 genera were dispersed via endozoochory. Orangutan fecal samples contained a mean of 1.17 genera (range 0-7). Germination experiments were conducted with orangutan defecated seeds and seeds from fruit. A significantly higher percent of orangutan defecated seeds germinated for 5 out of 6 genera than control seeds with pulp (p<0.01). A significantly higher percent of orangutan defecated seeds germinated for 3 out of 6 genera compared to control seeds without pulp (p<0.01). Gut transit times in wild orangutans ranged from 39.5 to 87 hours (n=6). Finally, we modeled seed dispersal distances using orangutan movement tracks (n= 30) with gut passage durations of 45 and 60 hours. Gut retention times of 45 hours resulted in a mean dispersal distance of 507 ± 123m (range 69 - 1341), and 60 hours resulted in a mean distance of 592 ± 115m (range 83 - 1260). We conclude orangutans are effective seed dispersers with similar efficacy to other great apes. Orangutans disperse a wide variety of genera over medium to long distances and gut passed seeds germinate at higher rates compared with controls. Keywords: Ecology, Seed dispersal effectiveness, Movement, Tropical, Asia Funders: National Science Foundation (BCS-1638823); National Geographic Society; US Fish and Wildlife Services (F19AP00798; F18AP00898); Disney Wildlife Conservation Fund 

Orangutans are large-bodied frugivores predicted to be effective seed dispersers. We studied Bornean orangutan (Pongo pygmaeus wurmbii) seed dispersal effectiveness, by measuring the quantity of seeds dispersed and the quality of dispersal in Gunung Palung National Park, Borneo, Indonesia (August 2018 to August 2019). For dispersal quality we conducted germination experiments, measured germination rates, and modeled dispersal distances. We systematically collected orangutan fecal samples, feeding behavior, and GPS tracks during focal follows. We sieved 549 fecal samples collected from 36 orangutans and identified the seeds, and of the fecal samples collected 75.2% contained seeds. A total of 24 genera were dispersed via endozoochory. Germination experiments were conducted with orangutan defecated seeds and seeds from fruits. A significantly higher percent of orangutan defecated seeds germinated for 5 out of 6 genera than control seeds with pulp (p<0.01). A significantly higher percent of orangutan defecated seeds germinated for 3 out of 6 genera compared to control seeds without pulp (p<0.01). Gut transit times in wild orangutans ranged from 39.5 to 87 hours. Finally, we modeled seed dispersal distances using orangutan movement tracks (n= 30) with gut passage durations of 45 and 60 hours. Gut retention times of 45 hours resulted in a mean dispersal distance of 507 ± 123m, and 60 hours resulted in a mean distances of 592 ± 115m. We conclude orangutans are effective seed dispersers, as orangutans disperse a wide variety of genera over medium to long distances and defecated seeds exhibit high germinability. Orangutans are large-bodied frugivores predicted to be effective seed dispersers. We studied Bornean orangutan (Pongo pygmaeus wurmbii) seed dispersal effectiveness, by measuring the quantity of seeds dispersed and the quality of dispersal in Gunung Palung National Park, Borneo, Indonesia (August 2018 to August 2019). For dispersal quality we conducted germination experiments, measured germination rates, and modeled dispersal distances. We systematically collected orangutan fecal samples, feeding behavior, and GPS tracks during focal follows. We sieved 549 fecal samples collected from 36 orangutans and identified the seeds, and of the fecal samples collected 75.2% contained seeds. A total of 24 genera were dispersed via endozoochory. Germination experiments were conducted with orangutan defecated seeds and seeds from fruits. A significantly higher percent of orangutan defecated seeds germinated for 5 out of 6 genera than control seeds with pulp (p<0.01). A significantly higher percent of orangutan defecated seeds germinated for 3 out of 6 genera compared to control seeds without pulp (p<0.01). Gut transit times in wild orangutans ranged from 39.5 to 87 hours. Finally, we modeled seed dispersal distances using orangutan movement tracks (n= 30) with gut passage durations of 45 and 60 hours. Gut retention times of 45 hours resulted in a mean dispersal distance of 507 ± 123m, and 60 hours resulted in a mean distances of 592 ± 115m. We conclude orangutans are effective seed dispersers, as orangutans disperse a wide variety of genera over medium to long distances and defecated seeds exhibit high germinability. Funders: National Science Foundation (BCS-1638823); National Geographic Society; US Fish and Wildlife Services (F19AP00798; F18AP00898); Disney Wildlife Conservation Fund 

Seed dispersal is a process essential for the maintenance and regeneration of tropical forests. Many primates are important seed dispersers, and orangutans are predicted to be important seed dispersers as they are large-bodied and highly frugivorous. However, minimal previous research has been conducted on orangutan seed dispersal behavior. Here, we present our preliminary analyses on orangutan (Pongo pygmaeus wurmbii) seed dispersal behavior. Our data were collected in Gunung Palung National Park in West Kalimantan from August 2018 to August 2019. We collected 549 wild Bornean orangutan fecal samples, of which 75.2% of the fecal samples contained intact seeds. Dispersed seeds ranged in length from 0.1mm to 32.5mm. Next, we used a comparative perspective to understand orangutan seed dispersal effectiveness by placing orangutans in the context of the other apes. Orangutans disperse seeds with similar frequency as some populations of chimpanzees and gorillas. Overall, orangutans appear to be effective seed dispersers based on quantitative seed dispersal measures. Orangutans appear to have a vital ecological role in tropical forests, thus we advocate for the conservation of wild orangutans and the forests they inhabit. Funders: National Science Foundation (BCS-1638823); National Geographic Society; US Fish and Wildlife Services (F19AP00798; F18AP00898); Disney Wildlife Conservation Fund 

Documenting the ways in which organisms physically move through space and the influences of habitat structure on their movement and posture are fundamental to understanding their spatial ecology. Movement ecology is thus a significant influence on animal cognition, morphology, diet, group structure, etc. Evidence to date demonstrates that orangutans of different species (Pongo abelii, P. wurmbii) living in similar habitats exhibit positional behavior more similar to each other than to conspecifics in disparate habitats. Therefore, it is a reasonable hypothesis that orangutan positional behavior is a function of habitat rather than morphological constraints. Here, we test this hypothesis by examining the positional behavior of orangutans living in Gunung Palung National Park in West Kalimantan, Indonesia, a primary forest mosaic composed of seven distinct habitats. We use 33,358 instantaneous scan samples collected every 5 minutes during full day follows of habituated adult orangutans (N=27) to examine postural behavior, locomotor modes, and structure use with a null hypothesis of no differences in positional behavior or support use profiles between habitats. We found significant differences in the profiles of orangutan postural behavior (G=216.2, p<0.001), locomotor behavior (G=45.34, p<0.001), and support use (G=137.8, p<0.001) in 5 distinct habitats within Gunung Palung National Park. Orangutans within the same population move through and use distinct habitats in different ways. This underscores the role of local ecology in structuring organisms’ space use as well as the importance of behavioral plasticity to primates’ movement ecology. Funding: 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 

Previous observational research on primate feeding ecology has demonstrated that some primates consume fruit in the morning and leaves in the afternoon. However, diurnal patterning of feeding bouts has not been demonstrated for many of the apes, nor for relatively solitary primates. Furthermore, whether this has nutritional consequences is unclear. Orangutans are largely frugivorous omnivores that also incorporate leaves, bark, pith, and insects in their diet. As primarily solitary animals, their foraging and food choices are not restricted by group size and group decisions – thus they provide an excellent species with which to examine individual ape foraging choices. In accord with previous research, we hypothesized that orangutans would select energy rich and easy to digest foods (i.e., fruit) in the morning, then move to leaves and more fibrous food sources later in the day in order to allow more digestion time, and possibly to gain necessary macronutrients at the optimal time. We examined whether orangutans exhibited diurnal patterning of feeding bouts using 51 full day follows of wild Bornean orangutans (Pongo pygmaeus wurmbii) occurring May 2015 – January 2016 at Gunung Palung National Park, West Kalimantan, Indonesia. While there is a statistically significant difference in food types eaten at different times of day (χ2 = 76.3, p = 0.03), this difference is driven by increased consumption of leaves and pith in the afternoon hours, while fruit is consistently consumed throughout the day. We discuss this in the contexts of optimal nutrient selection and the Geometric Framework of Nutrition. Funding: National Science Foundation (BCS-1638823; BCS-1613393), NSF GRFP (DGE-1247312); Boston University; National Geographic Society, US Fish and Wildlife (F15AP00812), Leakey Foundation, Disney Wildlife Conservation Fund; Wenner-Gren Foundation; Nacey-Maggioncalda Foundation 

Animal-mediated seed dispersal is important for promoting forest regeneration and sustainability. Animal movement influences the distribution of seeds across the environment, resulting in spatially aggregated seed dispersal patterns. Animal seed dispersal patterns likely play an important role in the spatial structuring of tree populations: where a seed disperser moves influences the seed distribution. Environmental parameters that shape a disperser’s movement also influence the spatial distribution pattern of their seed dispersal. Orangutans are highly frugivorous and have been shown to disperse intact viable seeds. GPS locations were recorded for all orangutan defecations (n=1721) from 2014 to 2016 at the Cabang Panti Research Station in Gunung Palung National Park (GPNP), Indonesia. Our pilot research at GPNP measured seeds in fecal samples (n=98 fecal samples) and demonstrated that orangutan fecal samples do have intact seeds in more than 95% of t heir feces. A kernel density map was made using the defecation data to calculate the spatial density distribution of the defecations. A geographically weighted regression model (GWR) analyzed how well spatial parameters (altitude, slope, distance to river, and normalized difference vegetation index) predict the spatial density distribution of orangutan seed dispersal. All parameters in the GWR were statistically significant (R2=0.80, p<0.001) and showed low values for collinearity. The results show that orangutan seed dispersal is aggregated in space and the seed dispersal pattern is significantly shaped by environmental variables. This study provides us a better understanding of how the environment plays a role in determining animal behavior which influences the seed spatial distribution. Funders include the National Science Foundation (BCS-1638823), National Geographic Society, US Fish and Wildlife (F15AP00812), Leakey Foundation, Disney Wildlife Conservation Fund, and Nacey-Maggioncalda Foundation. 

Orangutans consume large quantities of ripe fruit and disperse intact seeds over wide areas. However, few studies have quantified seed dispersal in orangutans (Galdikas 1982; Nielsen et al. 2012). We hypothesized that orangutans are effective seed dispersers. This was tested by identifying, measuring and counting seeds in orangutan feces and recording fecal coordinates to determine seed spatial distribution patterns. Orangutan feces were collected opportunistically from March- September 2015 at the Tuanan Research Station (n=97) and from July- August 2016 at the Cabang Panti Research Station in Gunung Palung National Park, Indonesia (n=98). The feces were sieved, seeds were counted, and seed morphotypes were identified in at least 96% of fecal samples. Flanged males, unflanged males, adult females, and juveniles independent enough from their mother to allow for fecal collection, were all observed dispersing seeds. Four fruit genera were dispersed at Cabang Panti and nine fruit genera were dispersed at Tuanan. At Cabang Panti, the largest intact seed size recorded was 2.29cm in length and the smallest seeds dispersed were less than 1mm Ficus seeds. At Tuanan, 31% of fecal samples had 2 or more genera, 42% had 1 genera, and 26% had no seeds. We used descriptive GIS to describe the spatial distribution of the dispersed seeds. We concluded that orangutans have an important role in fruit tree recruitment. They disperse intact seeds of varying sizes and disperse several different genera of seeds. Future research will measure seed dispersal distances and orangutan gut-passage rates to establish the orangutan seed shadow. Funders include the National Geographic Society, the Leakey Foundation, the US Fish and Wildlife Service, United States Agency for International Development, and the National Science Foundation (BCS-0936199). 

The Gunung Palung Orangutan Project has conducted research on critically endangered wild Bornean orangutans (Pongo pygmaeus wurmbii) since 1994 in Gunung Palung National Park, West Kalimantan, Indonesia. A major goal of our broad-ranging research on orangutan behavior and ecology is to understand how the unique rainforest environment of Southeast Asia, characterized by dramatic changes in fruit productivity due to unpredictable mast fruiting, impacts orangutan behavior, physiology, and health. Much of our research has been devoted to the development of non-invasive techniques and an integrated biology approach – using hormonal assays, fecal processing, nutritional analysis, genetics, and behavioral ecology – and has led to an increased understanding of the ecological and evolutionary pressures shaping orangutan adaptations. Our results show that the extended life history and very slow reproductive rate of orangutans are adaptations to their environment. Orangutans in the Gunung Palung landscape, as elsewhere across Borneo and Sumatra, also face a series of conservation challenges, including extensive habitat loss and the illegal pet trade. We highlight how our investigations of orangutan health status, ecosystem requirements, and the assessment of orangutan density using ground and drone nest surveys have been applied to conservation efforts. We describe our project’s direct conservation interventions of public education and awareness campaigns, sustainable livelihood development, establishment of village-run customary forests, investigation of the illegal pet trade, and active engagement with Indonesian government organizations. These efforts, in concert with the development of local scientific and conservation capacity, provide a strong foundation for further conservation as orangutans face a challenging future.