A mixed methods study of the habituation process in wild Bornean orangutans in West Kalimantan, Indonesia

In field primatology, habituation refers to the process of increasing the tolerance of wild primates to the presence of human observers via repeated non-threatening contact. The goal of habituation is for humans to be treated like a “neutral” element in the animals’ environment so that “natural” primate behavior can be observed. Therefore, the habituation process is regarded as a prerequisite to the collection of long-term behavioral data and biological samples that comprise the research programs of most wild primate field studies. However, the process of habituation itself is understudied, and there is little definitive knowledge about its behavioral and physiological impacts. In this dissertation, I present a detailed examination of the process of habituation in a population of wild Bornean orangutans living in Gunung Palung National Park in West Kalimantan, Indonesia. To do so, I explore the impacts of habituation from three distinct but intersecting perspectives: behavioral, physiological, and relational. Following the ethnoprimatological method, which emphasizes the human-nonhuman primate interface and employs a mixed-methods approach, I integrate findings from quantitative and qualitative data collected during my field work at Gunung Palung National Park during 2022-2023, as well as extensive behavioral data on this wild orangutan population collected by field assistants, volunteers, and researchers of the Gunung Palung Orangutan Project from 1994 to the present. In the first part of my study, I lay out a broad review of the habituation process in field primatology, including important definitions and common misconceptions of habituation and related terms, a brief history of the practice within primatology, and ethical considerations, including risks and benefits of habituation. I also discuss factors that influence how quickly and successfully a primate population can be habituated, as well as ways in which habituation has been studied and measured. The review concludes with a proposal to reframe how primate behavior is contextualized in primatological studies, distinguishing the study of habituated behavior from natural behavior. Next, I present an in-depth analysis of behavioral responses to the process of habituation in a population of wild orangutans. I compare the percentage of time spent in three activities—feeding, traveling, and resting—between habituated and unhabituated orangutans. These comparisons demonstrate that unhabituated adult orangutans spend a significantly smaller percentage of time eating and a significantly larger percentage of time traveling and resting than their habituated counterparts. This pattern persisted when the data was subset by age-sex class (adult females, flanged males, and unflanged males), and when controlling for fruit availability. Additional analysis confirms that both energetic and social costs of certain habituation behaviors predict which habituation response an orangutan is likely to employ: stay, flee, or vocalize only. Importantly, as predicted by the socioecological model, energetic and social costs are not experienced the same across age-sex classes in orangutans, including between the two male morphs. To study the physiological impact of habituation in wild Bornean orangutans, I compare urinary cortisol levels between unhabituated orangutans and habituated orangutans within and across age-sex classes. I also compare these same groups using a measurement of the relative strength of the stress response (demonstrated reactive scope), which calculates the size of the range of urinary cortisol levels for a group, as well as the variability of urinary cortisol levels within the range. While I predicted both types of analyses to show a significant difference between unhabituated and habituated orangutans, the direct comparison of urinary cortisol levels between habituated and unhabituated orangutans showed no significant difference. However, the unhabituated orangutans did show a greater range of urinary cortisol levels and a higher variability within that range compared to habituated orangutans, indicating that unhabituated orangutans are experiencing a more frequent or intense stress response. This pattern for the demonstrated reactive scope persisted for almost every age-sex class in the study, divided by habituation status. In a statistical model, habituation status did not significantly explain the variability in urinary cortisol levels. Instead, age-sex class and fruit availability, as well as the interaction between these, best predicted differences in cortisol levels, along with the random effect of individual orangutan. These findings highlight the impact of sexually-differentiated energetic and social costs, as well as the importance of individual traits on urinary cortisol levels in wild Bornean orangutans. Overall, these results indicate an adaptive response by wild Bornean orangutans in the face of an unpredictable and uncontrollable stressor: sudden and extended human presence during the habituation process. Lastly, I analyzed qualitative data I collected during my time in the field, integrating it with the results from my analyses of quantitative behavioral and hormonal data. The basis of my qualitative analysis were the themes, relevant quotes, and passages identified via descriptive coding of my raw data: ethnographic field notes, transcripts from interviews with Indonesian field assistants, and ad lib comments that accompanied behavioral data compiled in the GPOP database. The synthesis of my qualitative and quantitative data corroborated the results from the statistical analyses of habituation response behaviors and urinary cortisol measurements, supporting the use of mixed-methods approach within an ethnoprimatological framework. Collectively, these results support the rejection of habituation as a one-way observation by a neutral observer of natural behavior in a primate research subject. Instead, the habituation process is a relational one in which humans and nonhuman primates shape each other’s experiences and understandings of each other; it is impacted both by the socioecology and individual traits of the animals, and the perspectives and backgrounds of the humans involved.

Author dc:creator

• Brubaker-Wittman, Laura Anne

Advisor dc:contributor.advisor

• Knott, Cheryl D.

• Behavioral sciences
• Animal sciences
• Cultural anthropology
• Ethnoprimatology
• Habituation
• Orangutan
• Primatology

Statement dc:rights

• Attribution-NonCommercial 4.0 International

Licence dc:rights.uri

• http://creativecommons.org/licenses/by-nc/4.0/

Language dc:language.iso

en_US

Handle dc:identifier.uri

https://hdl.handle.net/2144/53267

OAI identifier oai:identifier

oai:open.bu.edu:2144/53267