Cheryl D Knott

Boston University | BU · Department of Anthropology

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 oppor...

Intersexual conflicts over mating can engender antagonistic coevolution of strategies, such as coercion by males and selective resistance by females. Orangutans are exceptional among mammals for their high levels of forced copulation. This has typically been viewed as an alternative mating tactic used by the competitively disadvantaged unflanged ma...

Orangutans (Pongo spp.) are reported to have extremely slow life histories, including the longest average interbirth intervals of all mammals. Such slow life history can be viable only when unavoidable mortality is kept low. Thus, orangutans’ survivorship under natural conditions is expected to be extremely high. Previous estimates of orangutan lif...

Infanticide as a male reproductive tactic is widespread across mammals, and is particularly prevalent in catarrhine primates. While it has never been observed in wild orangutans, infanticide by non-sire males has been predicted to occur due to their extremely long inter-birth intervals, semi-solitary social structure, and the presence of female cou...

Environmental education is a cornerstone of many wildlife conservation programs, and measuring the impact of such education initiatives is imperative for evaluating their effectiveness in achieving conservation goals. For over 15 years, the Gunung Palung Orangutan Conservation Program (GPOCP) has been working to protect wild Bornean orangutans Pong...

Gunung Palung National Park (GPNP) and the surrounding region in West Kalimantan, Indonesia, host a significant population of Critically Endangered Bornean orangutans ( Pongo pygmaeus wurmbii ) amidst various conservation challenges, including habitat destruction, the illegal pet trade, and human-wildlife conflict. The Gunung Palung Orangutan Conse...

Male orangutans (Pongo spp.) exhibit bimaturism, an alternative reproductive tactic, with flanged and unflanged males displaying two distinct morphological and behavioral phenotypes. Flanged males are larger than unflanged males and display secondary sexual characteristics which unflanged males lack. The evolutionary explanation for alternative rep...

Sexually-selected infanticide by males is widespread across primates. Maternal protection is one of many infanticide avoidance strategies employed by female primates. Bornean orangutan (Pongo pygmaeus wurmbii) mothers with younger offspring are less social with males than mothers with older offspring. Additionally, the distance between a mother and...

Research in primate nutritional ecology uses concepts of quality, preference, and energy content to explain food choice: a primate consumes high-quality, preferred, and/or high-energy foods when available, and moves to other foods when they are not. Many frugivorous primates are thought to maximize energy, suggesting that high-energy fruit is a qua...

Bellucia pentamera Naudin (Famili: Melastomataceae), atau dikenal dengan nama lokal jambu perancis, kardia, dan harendong gede merupakan jenis tumbuhan invasif yang ditemukan di Taman Nasional Gunung Palung (TNGP). Jenis ini banyak dijumpai di TNGP selama dua dekade terakhir dan telah meningkatkan kekhawatiran tentang potensi dampak negatif pada ke...

We constructed a parallel laser photogrammetry apparatus constructed from commercially available parts, and measured forearm lengths and flange widths of 16 wild Bornean orangutans. Our objectives were to validate our method and apparatus, discuss issues encountered, and construct preliminary growth curves. For adult males, we also compared flange...

Knowledge of species-typical reproductive endocrinology profiles is crucial for testing hypotheses pertaining to the evolutionary history, reproductive parameters, and life history of a species, and for managing the well-being of individual animals in human care. Large-scale empirical measurements of ovarian hormones, however, are rare for most pri...

In humans, individuals’ social setting determines which and how language is acquired. Social seclusion experiments show that sociality also guides vocal development in songbirds and marmoset monkeys, but absence of similar great ape data has been interpreted as support to saltational notions for language origin, even if such laboratorial protocols...

Conservation strategies are rarely systematically evaluated, which reduces transparency, hinders the cost-effective deployment of resources, and hides what works best in different contexts. Using data on the iconic and critically endangered orangutan (Pongo spp.), we developed a novel spatiotemporal framework for evaluating conservation investments...

Laboratory methods are increasingly being used in remote field camps, or during mobile field surveys, to aid in wildlife conservation. This chapter explains how field laboratories have allowed for technological advances in sample preparation and preservation, and for both low and high-tech on-site analysis. It highlights how field samples can be us...

The global loss of biodiversity is occurring at an unprecedented pace. Despite the considerable effort devoted to conservation science and management, we still lack the basic data on the distribution and density of most animal and plant species, which in turn hampers our efforts to study changes over time. In addition, we often lack behavioural dat...

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 A...

Ecologists and conservation biologists conducting long-term research programs in the tropics must confront serious ethical challenges that revolve around economic inequalities, cultural differences, supporting the local communities as much as possible, and sharing the knowledge produced by the research. In this collective article, researchers share...

Using data on the iconic orangutan (Pongo spp.), we developed a novel spatiotemporal framework for evaluating conservation investments. We show that around USD 1 billion was invested between 1999 and 2019 into orangutan conservation by governments, non-governmental organizations, companies and communities. Broken down by allocation to different con...

The Marginal Value Theorem (MVT) is an integral supplement to Optimal Foraging Theory (OFT) as it seeks to explain an animal's decision of when to leave a patch when food is still available. MVT predicts that a forager capable of depleting a patch, in a habitat where food is patchily distributed, will leave the patch when the intake rate within it...

This commentary emerged from a panel presentation at the International Primatological Society Congress in Nairobi, Kenya, 2018. The goal was to provide regional updates on the status of primate removal from habitat countries, especially for the pet trade, and develop guidelines that could help primatologists address this critical problem. The trade...

The primate adolescent period is characterized by a series of changes in physiology, behavior, and social relationships. Orangutans have the slowest life history and the longest period of dependency of all primates. As members of a semisolitary species with high levels of sexual coercion, adolescent female orangutans face a unique combination of ch...

Sexually selected infanticide by males is widespread in primates. Female primates employ a variety of strategies to reduce infanticide risk. While infanticide has never been directly observed in wild orangutans (Pongo spp.), their slow life history makes infants vulnerable to infanticide. The mating strategies of female orangutans include polyandro...

Bornean orangutans (Pongo pygameus wurmbii) have historically been characterized as frugivores and energy maximizers under an optimal foraging paradigm. While orangutans do consume more fruit and energy when fruit is available, the Geometric Framework of Nutrition (GF) suggests that energy maximization is not the only goal of foraging. Instead, GF...

Body temperature (Tb) is a valuable measure of health and metabolic status in primates, and can be used for integrative analyses of behavior (e.g., to assess costs of intrasexual competition). However, data on Tb in wild great apes are scarce, as conventional measures of Tb are invasive. A largely overlooked but effective proxy for Tb is fecal temp...

Sexual coercion is the use by a male of force, or threat of force, to secure a mating with a female, decreasing her chances of mating with other males and inflicting a cost on the female. It is a third type of sexual selection and falls under sexual conflict theory. Three forms of sexual coercion are recognized. Direct coercion includes forced copu...

Why did our ancestors combine the first consonant- and vowel-like utterances to produce the first syllable or word? To answer this question, it is essential to know what constituted the communicative function of proto-consonants and of proto-vowels before their combined use became universal. Almost nothing is known, however, about consonant-like ca...

Poaching for the pet trade is considered one of the main threats to orangutan survival, especially to the Bornean species (Pongo pygmaeus). However, there have been few attempts to quantify the number of individuals taken from the wild or to evaluate the drivers of the trade. Most orangutan poaching is thought to be opportunistic in nature, occurri...

Bornean orangutans (Pongo pygmaeus wurmbii) are described as opportunistic feeders consuming mostly fruit, as frugivores who will feed on fruit when available, and as energy maximizers when fruit is available. Newer geometric foraging theory suggests additional complexity in feeding behavior - that most animals balance nutrients and attempt to main...

The male orangutan long call is the center of many questions about signaling in primate studies. Most research suggests that the long call functions to (1) maintain male-male spacing and competition and (2) attract females. Previous research has primarily been conducted in Sumatra, and the function of Bornean male orangutan long call is a topic of...

Publication of primate data is sometimes years after the fact, impeded by delays due to manual data entry and analysis. However, technology is changing as quickly as the rainforest is disappearing, presenting opportunities to implement new time-saving methodologies. We thus piloted the use of iPads for data collection in our study of wild orangutan...

Due to their solitary nature, aggressive encounters between wild orangutans are rarely witnessed, yet we commonly see evidence of physical antagonism in wounding patterns exhibited in male, and occasionally female, orangutans. Male-male aggression is primarily thought to be over access to females, but information has been largely anecdotal. Here we...

Wild Bornean orangutans occasionally drink directly from water sources, but they depend largely on dietary water. However, few studies have investigated the water content of orangutan foods and its implications for food selection. Using feeding bouts and food samples from 39 full day follows (518 feeding bouts, 10 focal animals) in Gunung Palung Na...

Arbitrariness is an elementary feature of human language, yet seldom an object of comparative inquiry. While arbitrary signals for the same function are relatively frequent between animal populations across taxa, the same signal with arbitrary functions is rare and it remains unknown whether, in parallel with human speech, it may involve call produ...

Number of subjects per age-sex class and habituation level. (DOCX)

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...

Male orangutans (Pongo spp.) display an unusual characteristic for mammals in that some adult males advance quickly to full secondary sexual development while others can remain in an adolescent-like form for a decade or more past the age of sexual maturity. Remarkably little is understood about how and why differences in developmental timing occur....

Orangutan (Pongo spp.) males exhibit a remarkable degree of phenotypic plasticity in the timing of secondary sexual character development. While some males move quickly into the "flanged" morph, others retain an adolescent-like form for years past sexual maturity. Remarkably little is understood about these differences in developmental timing. Chan...

The rapid disruption of tropical forests probably imperils global biodiversity more than any other contemporary phenomenon. With deforestation advancing quickly, protected areas are increasingly becoming final refuges for threatened species and natural ecosystem processes. However, many protected areas in the tropics are themselves vulnerable to hu...

Female orangutan ranging behavior is highly variable. Estimates of home-range yield figures from 40 to >850ha, and differ between and within habitat types and research. Further, though orangutans are semi-solitary animals, adult female orangutans have considerable range overlap. We examine whether, within Gunung Palung National Park (West Kalimanta...

Protein is a limiting resource that is essential to the growth, maintenance and reproduction of tropical frugivores, yet few studies have examined how wild animals maintain protein balance. During chronic periods of fruit scarcity, Bornean orangutans (Pongo pygmaeus) often catabolize their own fat reserves despite unusually low metabolic requiremen...

The vital role of body protein as an energy reserve has received little focus in studies of wild primates. Owing to the relatively low protein content of fruit, some frugivorous primates could face a protein deficit if body protein is catabolized for energy during periods of low fruit availability. Such an imbalance can be detected if fatty acids,...

Recent comparative work has claimed the presence of socially transmitted behavioral innovations, ranging from tool use to sounds produced during nest building, i.e. culture, among wild orangutans. Much independent information is corroborating this interpretation. Here, after discussing the possible sources of error in this geographic approach, the...

Sundaland, a tropical hotspot of biodiversity comprising Borneo and Sumatra among other islands, the Malay Peninsula, and a shallow sea, has been subject to dramatic environmental processes. Thus, it presents an ideal opportunity to investigate the role of environmental mechanisms in shaping species distribution and diversity. We investigated the p...

During human evolutionary history, and for many around the world, breast milk is the primary source of nutritional energy for infants. Variation in breast milk quality might logically have important effects on infant health, growth, and development, yet the sources of this variation remain largely unelucidated. We quantified nutrient and energy con...

Orangutans have the longest interbirth interval of any mammal, with existing data suggesting that these intervals may be significantly longer in Sumatra than in Borneo. This finding presents a paradox because our models of reproductive ecology suggest that the higher habitat quality of Sumatra should lead to shorter interbirth intervals. This chapt...

This chapter explores variation in orangutan diets across their range, based on food lists. The authors of the chapter consolidated orangutan food lists from all available long-term field sites (N = 15). They represent both islands, multiple habitat types, varied degrees of degradation, and wild and rehabilitant populations. The chapter assesses th...

Adult female orangutans have large but stable home ranges, varying from as little as 150 ha in some forests up to 850 or more in others. Spatial variation in availability of fruit of key tree species or spatial variation in habitat-wide fruiting peaks appears to be the driving force behind major movements within the range. Larger home ranges are fo...

Orangutans are a species with a very pronounced sexual dimorphism, in that fully grown males are about twice the size of females, but adult, sexually mature males come in two distinct morphs. Unflanged males lack the secondary sexual characteristics (e.g., cheek flanges, throat sack, long call) of the flanged males, but are sexually active, fertile...

The chapter examines differences in the activity budgets of wild orangutans (Pongo spp.) within and between a large number of study sites in Sumatra and Borneo. The authors of the chapter found that each orangutan population appeared to follow one of two distinct foraging strategies: either (1) ‘sit and wait’, in which orangutans aim to minimize th...

Orangutans are a species with a very pronounced sexual dimorphism, in that fully grown males are about twice the size of females, but adult, sexually mature males come in two distinct morphs. Unflanged males lack the secondary sexual characteristics (e.g., cheek flanges, throat sack, long call) of the flanged males, but are sexually active, fertile...

This chapter provides an overview of the sounds and vocalizations that Sumatran and Bornean orangutans produce. The current data set indicates that there are at least 32 different orangutan sounds and vocalizations that can be distinguished. Interestingly enough not all of these are produced by all individuals in all populations and several occur o...

Orangutans and chimpanzees differ in many aspects of their mating and social systems. Nevertheless, because both great apes require enormous maternal investment in offspring and because female reproductive potential is limited, female orangutans and chimpanzees should be selective of their mates, yet expected to exhibit anti-infanticide strategies...

The mostly solitary ranging of orangutans and the large areas over which they traverse have hampered quantification of Bornean orangutan ranging patterns and feeding competition. Because of their semisolitary existence, female orangutans have few competitive interactions among themselves. However, contest and scramble types of competition occur, an...

In recognition of the fact that orang-utans (Pongo spp.) are severely threatened, a meeting of orang-utan experts and conservationists, representatives of national and regional governmental and non-governmental organizations, and other stakeholders, was convened in Jakarta, Indonesia, in January 2004. Prior to this meeting we surveyed all large are...

Assessment of energetic condition is a critical tool for behavioral and reproductive ecologists. However, accurate quantification of energy intake and expenditure is labor-intensive, and it can be problematic for field scientists to obtain regular data on individual animals. C-peptide, a polypeptide segment of the proinsulin molecule that is secret...

Across broad taxonomic groups, life history models predict that increased ecological predictability will lead to conservative investment in reproductive effort. Within species, however, organisms are predicted to have increased reproductive rates under improved environmental conditions. It is not clear how these models apply to closely-related spec...

The emergence of the genus Homo is widely linked to the colonization of 'new' highly seasonal savannah habitats. However, until recently, our understanding of the possible impact of seasonality on this shift has been limited because we have little general knowledge of how seasonality affects the lives of primates. This 2005 book documents the exten...

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 t...