A survey of the orangutan Pongo pygmaeus pygmaeus population in and around Gunung Palung National Park, West Kalimantan, Indonesia based on nest counts
Johnson A, Knott CD, Pamungkas B, Pasaribu M, Marshall A
BIOLOGICAL CONSERVATION
121(4): 405-507 FEB 2005

Abstract:
We conducted the first orangutan population census of Gunung Palung National Park, West Kalimantan, Indonesia, between April and September 2001. We used a refined line-transect nest-count methodology utilizing transect recounts to survey 69 km at 14 sites within the park and 14.2 km in the buffer zone. We present the first Bornean orangutan density estimate using complete site-specific parameters and long term monitoring of nest decay rates. Average orangutan density was 3.0 individuals/km2, with densities ranging from 2.4 ind/km2 in montane forest to 4.1 ind/km2 in primary peat swamp. In addition, we tested alternative approaches to calculation of the nest-duration parameter. The second count of each transect resulted in 30% higher density estimates overall. We conclude that recounts should be incorporated into standard line-transect methodology. We estimate there to be ≈2500 individual orangutans in Gunung Palung, indicating the importance of this site in plans to conserve a network of viable orangutan populations. While logging may reduce densities, disturbed forest both inside and adjacent to the park has high conservation value as orangutan habitat. Further research into long-term orangutan population persistence in disturbed forest is needed.

 

Radioimmunoassay of estrone conjugates from urine dried on filter paper
Knott CD
AMERICAN JOURNAL OF PRIMATOLOGY
67(1): 121-135 SEP 2005

Abstract:
Hormonal analysis of urine from free-ranging primates has been limited due to the difficulty of preserving samples under field conditions. Drying urine on filter paper is an alternative for field preservation. This study describes a new laboratory method for eluting steroids from filter paper with methanol, along with a series of experiments used to develop and validate this method. The overall elution recovery of estrone sulfate (ES) from filter paper was 86.4%. Estrone conjugate (E1C) levels in humans and captive orangutans were analyzed by radioimmunoassay (RIA). Values from samples dried on filter paper were significantly correlated with values from matched frozen samples, with elution efficiencies ranging between 97.1% and 102.4%. Creatinine (Cr) measurements from frozen urine compared to urine dried on filter paper were also significantly correlated (r=0.96) with an elution efficiency of 101.7%. After the samples were stored for 2 years, the absolute values of E1C and Cr were significantly lower but were still significantly correlated with frozen urine values. These data demonstrate the effectiveness of filter paper as a medium for preserving urinary steroid samples, and the efficiency of methanol as a solvent for eluting E1C and Cr. This method thus provides a viable alternative to the traditional procedure of freezing urine for field studies, where freezers are not available.

 

Orangutan cultures and the evolution of material culture
Van Schaik CP, Ancrenaz M, Borgen G, Galdikas B, Knott CD, Singleton I, Suzuki A, Utami SS, Merrill M
SCIENCE
299 (5603): 103-105 JAN 3 2003

Abstract:
Geographic variation in some aspects of chimpanzee behavior has been interpreted as evidence for culture. Here we document similar geographic variation in orangutan behaviors. Moreover, as expected under a cultural interpretation, we find a correlation between geographic distance and cultural difference, a correlation between the abundance of opportunities for social learning and the size of the local cultural repertoire, and no effect of habitat on the content of culture. Hence, great-ape cultures exist, and may have done so for at least 14 million years.

 

Geographic variation in tool use on Neesia fruits in orangutans
Van Schaik CP, Knott CD
AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY
114 (4): 331-342 APR 2001


Abstract:
Geographic variation in the presence of skilled behavior may reflect geographic variation in genetic predispositions or ecological conditions (accompanied by reliable expression during development), or it may reflect the vagaries of invention and the appropriate social conditions for persistence. In this study, we compare the feeding techniques and tool-using skills used by orangutans to extract the nutritious seeds from Neesia fruits between Suaq Balimbing on Sumatra and Gunung Palung on Borneo, and map the distribution of Neesia tool use in Sumatran swamps. We show that neither genetics nor ecology is sufficient to explain the distribution of this tool use, confirming earlier findings on chimpanzees. We conclude that the ability to learn to use tools determines the geographic distribution. It is impossible to distinguish between the history of invention and the conditions for social transmission as the causal factors, but the high density and the social tolerance at Suaq Balimbing create propitious conditions for the maintenance of the skill as a tradition once it has been invented. High orangutan densities in the other Sumatran coastal swamps with Neesia tool use support the conclusion that suitable transmission conditions are the critical factor to explain the geographic distribution of skills such as feeding tool use.


Changes in orangutan caloric intake, energy balance, and ketones in response to fluctuating fruit availability
Knott CD
INTERNATIONAL JOURNAL OF PRIMATOLOGY
19 (6): 1061-1079 DEC 1998

Abstract:
I used novel quantitative measures to assess the impact of fruit seasonality on changes in diet and energy balance during 4918 hours of observation on >60 orangutans in Gunung Palung National Park, West Kalimantan, Indonesia, from September 1994 through September 1995. During this period a mast fruiting occurred resulting in large fluctuations in fruit availability measured by monitoring of 558 orangutan fruit trees. Orangutan diet varied tremendously in accordance with these fluctuations. During the month of highest fruit production, 100% of the orangutan diet was composed of fruit. In contrast, during the fruit-poor period as little as 21% of the diet was fruit, while 37% was bark. Nutritional analyses of 78 of the foods most commonly eaten during this study show that mast foods were significantly higher in caloric content than were nonmast foods, which translates into substantial changes in caloric intake. During the month of highest fruit consumption (January), males consumed an estimated 8422 kcal/day and females consumed 7404 kcal/day. During the month of lowest fruit consumption (May), males consumed 3824 kcal/day and females consumed 1793 kcal/day. These differences were significantly different between the 2 months for both males and females. In May, males ate significantly more kcal/day than females did. Time spent feeding did not differ between the two periods for either males or females. I assessed the impact of these changes in diet and caloric intake on orangutan physiological functioning by measuring ketones in 257 urine samples collected from adult males and females. Ketones-products of fat metabolism-were present in urine only during the fruit-poor period. These data suggest that orangutans are highly efficient at storing far during fruit-rich periods and utilizing the reserves during times of fruit shortfall. This response may have important implications for orangutan survivorship, reproduction, and behavior.

Interactions between energy balance, hormonal patterns and mating behavior in wild Bornean orangutans (Pongo pygmaeus).
Cheryl D. Knott
AMERICAN JOURNAL OF PRIMATOLOGY 42(2):124 1997

Abstract:
This study investigated the hypothesis that changes in energy balance have a significant effect on orangutan hormonal functioning and mating behavior. Data were collected on wild orangutans in Gunung Palung National Park, Indonesian Borneo, starting in August 1994 and are based on 8000 hours of observation of 60 animals. Orangutan feeding and activity patterns were monitored, and foods were collected and analyzed for metabolizable energy. Energy balance was assessed through changes in caloric intake and the presence of urinary ketones (indicating fat catabolism). Changes in fruit availability were monitored in 558 orangutan fruit trees. Non-invasive methods of collecting and preserving urine were developed and urinary estrone conjugates (E1C) were measured using radioimmunoassay for hormonal evaluation. Mating was broken down into component behaviors. Results revealed significant (p=.001) fluctuations in fruit, leading to dramatic changes in diet and caloric intake (p=.003). Ketones were present in significantly more urine samples during fruit shortages (p=.0002). During periods of high fruit and positive energy balance, estrone conjugates were significantly higher (p<.05) than during fruit poor periods. These data suggest that changes in energy balance, due to dietary shifts have a significant impact on ovarian function. All matings were observed during periods of high food availability and higher average E1C levels. Most copulations were with sub-adult males and could not be easily categorized as “forced” vs. “consensual.”

The effects of changes in food availability on diet, activity, and hormonal patterns in wild Bornean orangutans (Pongo pygmaeus)
Cheryl D. Knott
AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY Supplement 24: 145 1997
Abstract:
This study tested the hypothesis that energetic status and female reproductive function in orangutans are modulated by changes in fruit availability. This research was conducted on wild orangutans in Gunung Palung National Park, Indonesian Borneo, starting in August 1994 and is based on over 6000 hours of observation. Non-invasive methods of measuring hormones in urine and assessing physiological status through chemical reagent strips were utilized. From November of 1994 through February of 1995 the forest at GP experienced a "mast fruiting" period of high flower and fruit availability. These changes were assessed through monthly monitoring of 558 orangutan fruit trees. During the 3 months of peak fruit abundance, orangutans spent 98-100% of feeding time eating energy rich seeds and pulp. In contrast, when fruit availability reached a low several months later, seeds and pulp composed only 21% of the diet. The remainder was made up of 37% bark, 25% leaves, 10% pith, and 7% insects. All foods eaten by orangutans were analyzed for metabolizable energy, revealing that caloric intake was significantly higher during the mast period. Activity patterns and energy expenditure varied in accordance with fluctuations in diet and fruit availability. During periods of high fruit availability, orangutans spent significantly more time foraging, but did so within a small day range. As fruit availability decreased, average day range increased as they searched for fruit over a larger area. During severe fruit shortage, day range shrank as orangutans fed on low quality, but abundant, bark and leaves. The effects of these energetic changes on orangutan physiology were assessed through a number of non- invasive techniques using urine. Over 400 urine samples were obtained from over 60 orangutans by placing plastic sheets beneath individuals during urination. Urine was dried on filter paper for later hormonal analysis. Urinary reagent strips were used to assess changes in physiological status. Ketones, a measure of fat metabolism, were present in siginficanly more urine samples during the non-mast period. Estrone conjugates were measured using radioimmunoassay to asses changes in ovarian function as a result of changing energetic status.

Monitoring health status of wild orangutans through field analysis of urine
Cheryl D. Knott
AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY Supplement 22: 139-140, 1996

Abstract:
Disease is recognized as a critical factor that can affect primate behavior, yet few methods allow for the quantification of disease states in wild primates. This paper reports on the use of urinary test strips to detect the presence of disease and monitor physiological status in wild orangutans. Urine was collected from wild orangutans at Gunung Palung National Park, Indonesian Borneo, between August 1994 and August 1995. A total of 387 urine samples were obtained from over 43 orangutans by placing plastic sheets beneath individuals during urination. Boehringer Mannheim urinary test strips were used to evaluate specific gravity, leukocytes, nitrite, pH, ketones, protein, glucose, urobilinogen, bilirubin and blood. Objectives of using these test strips were (1) to evaluate the presence of disease (2) to detect signs of nutritional stress (3) to monitor the occurrence of menstruation and (4) to use specific gravity as a measure of urine concentration for hormonal analysis.