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Examining how animals direct social learning during skill acquisition under natural conditions, generates data for examining hypotheses regarding how transmission biases influence cultural change in animal populations. We studied a population of macaques on Koram Island, Thailand, and examined model-based biases during interactions by unskilled individuals with tool-using group members. We first compared the prevalence of interactions (watching, obtaining food, object exploration) and proximity to tool users during interactions, in developing individuals (infants, juveniles) versus mature non-learners (adolescents, adults), to provide evidence that developing individuals are actively seeking information about tool use from social partners. All infants and juveniles, but only 49% of mature individuals carried out interacted with tool users. Macaques predominantly obtained food by scrounging or stealing, suggesting maximizing scrounging opportunities motivates interactions with tool users. However, while interactions by adults was limited to obtaining food, young macaques and particularly infants also watched tool users and explored objects, indicating additional interest in tool use itself. We then ran matrix correlations to identify interaction biases, and what attributes of tool users influenced these. Biases correlated with social affiliation, but macaques also preferentially targeted tool users that potentially increase scrounging and learning opportunities. Results suggest that social structure may constrain social learning, but the motivation to bias interactions towards tool users to maximize feeding opportunities may also socially modulate learning by facilitating close proximity to better tool users, and further interest in tool-use actions and materials, especially during development.

Archaeologists have used stone transport as a proxy to understand a variety of cognitive, logistical and social problems faced by human ancestors. In the same way, tool transport in our close relatives, non-human primates, has been seen as an important indicator of material selection proclivities, and as a contributing factor to the formation of activity sites as part of niche construction processes. Non-human primate transport behaviour also assists in framing evolutionary scenarios for the emergence of stone tool use in the hominin lineage. Here, we present the first study of directly observed stone tool transport in wild and unhabituated Burmese long-tailed macaques ( Macaca fascicularis aurea ) in Thailand. These macaques were observed during intertidal foraging activities, during which they pound open hard-shelled molluscs with stone tools. We recorded 2449 transport bouts, when a long-tailed macaque carried a stone tool from one prey target to the next, and found that on average the same tool was used to sequentially consume nine prey items in each foraging episode. The maximum number of prey items consumed in a single episode was 63. We found that tools used to open sessile oysters typically were used to consume more prey per episode than those employed on motile prey, and females transported tools further than males. Heavier tools (> 200 g) were rarely transported more than a few metres, but the longest transport distance was over 87 m. Importantly for primate archaeological analysis of macaque tool use sites, we found that the median transport distance was 0.5 m, meaning that tools are very often used in the immediate vicinity of the place they were collected by a macaque.

Since its inception, archaeology has traditionally focused exclusively on humans and our direct ancestors. However, recent years have seen archaeological techniques applied to material evidence left behind by non-human animals. Here, we review advances made by the most prominent field investigating past non-human tool use: primate archaeology. This field combines survey of wild primate activity areas with ethological observations, excavations and analyses that allow the reconstruction of past primate behaviour. Because the order Primates includes humans, new insights into the behavioural evolution of apes and monkeys also can be used to better interrogate the record of early tool use in our own, hominin, lineage. This work has recently doubled the set of primate lineages with an excavated archaeological record, adding Old World macaques and New World capuchin monkeys to chimpanzees and humans, and it has shown that tool selection and transport, and discrete site formation, are universal among wild stone-tool-using primates. It has also revealed that wild capuchins regularly break stone tools in a way that can make them difficult to distinguish from simple early hominin tools. Ultimately, this research opens up opportunities for the development of a broader animal archaeology, marking the end of archaeology's anthropocentric era.

The discovery of oil palm ( Elaeis guineensis ) nut-cracking by wild long-tailed macaques ( Macaca fascicularis ) is significant for the study of non-human primate and hominin percussive behaviour. Up until now, only West African chimpanzees ( Pan troglodytes verus ) and modern human populations were known to use stone hammers to crack open this particular hard-shelled palm nut. The addition of non-habituated, wild macaques increases our comparative dataset of primate lithic percussive behaviour focused on this one plant species. Here, we present an initial description of hammerstones used by macaques to crack oil palm nuts, recovered from active nut-cracking locations on Yao Noi Island, Ao Phang Nga National Park, Thailand. We combine a techno-typological approach with microscopic and macroscopic use-wear analysis of percussive damage to characterize the percussive signature of macaque palm oil nut-cracking tools. These artefacts are characterized by a high degree of battering and crushing on most surfaces, which is visible at both macro and microscopic levels. The degree and extent of this damage is a consequence of a dynamic interplay between a number of factors, including anvil morphology and macaque percussive techniques. Beyond the behavioural importance of these artefacts, macaque nut-cracking represents a new target for primate archaeological investigations, and opens new opportunities for comparisons between tool using primate species and with early hominin percussive behaviour, for which nut-cracking has been frequently inferred.

Anthropogenic disturbances have a detrimental impact on the natural world; the vast expansion of palm oil monocultures is one of the most significant agricultural influences. Primates worldwide consequently have been affected by the loss of their natural ecosystems. Long-tailed macaques (Macaca fascilularis) in Southern Thailand have, however, learned to exploit oil palm nuts using stone tools. Using camera traps, we captured the stone tool behavior of one macaque group in Ao Phang-Nga National Park. Line transects placed throughout an abandoned oil palm plantation confirmed a high abundance of nut cracking sites. Long-tailed macaques previously have been observed using stone tools to harvest shellfish along the coasts of Thailand and Myanmar. The novel nut processing behavior indicates the successful transfer of existing lithic technology to a new food source. Such behavioral plasticity has been suggested to underlie cultural behavior in animals, suggesting that long-tailed macaques have potential to exhibit cultural tendencies. The use of tools to process oil palm nuts across multiple primate species allows direct comparisons between stone tool using nonhuman primates living in anthropogenic environments. Electronic supplementary material The online version of this article (10.1007/s10764-017-9985-6) contains supplementary material, which is available to authorized users.

Tool use has allowed humans to become one of the most successful species. However, tool-assisted foraging has also pushed many of our prey species to extinction or endangerment, a technology-driven process thought to be uniquely human. Here, we demonstrate that tool-assisted foraging on shellfish by long-tailed macaques (Macaca fascicularis) in Khao Sam Roi Yot National Park, Thailand, reduces prey size and prey abundance, with more pronounced effects where the macaque population size is larger. We compared availability, sizes and maturation stages of shellfish between two adjacent islands inhabited by different-sized macaque populations and demonstrate potential effects on the prey reproductive biology. We provide evidence that once technological macaques reach a large enough group size, they enter a feedback loop – driving shellfish prey size down with attendant changes in the tool sizes used by the monkeys. If this pattern continues, prey populations could be reduced to a point where tool-assisted foraging is no longer beneficial to the macaques, which in return may lessen or extinguish the remarkable foraging technology employed by these primates. Published version

More than 3 million years of excavated archaeological evidence underlies most major insights into the evolution of human behaviour. However, we have seen almost no use of archaeological excavation to similarly broaden our understanding of behaviour in other animal lineages. The few published examples include recovery of a late Holocene assemblage of stones from the Ivory Coast, attributed to the agency of both humans (Homo sapiens) and chimpanzees (Pan troglodytes verus), and exploration of the occupation sites of nontool-using species such as penguins and other birds. The development of viable methods for identifying and interpreting past non-human tool use landscapes is essential if we are to gain a better understanding of technological evolution within other animals, including our close relatives, the primates. Recently, the growth of primate archaeology has built on the close phylogenetic relationship between humans and other primates to begin filling in this lacuna. Here, we present thefirst report on an archaeologically excavated Old World monkey tool use site, which was created by wild Burmese long-tailed macaques (Macaca fascicularis aurea) during shellfish-processing activities in coastal Thailand. These macaques use stone and shell pounding tools to access a wide variety of coastal and inter-tidal resources, including shellfish, crabs and nuts, and previous work has demonstrated that use-wear on the stone tools permits reconstruction of past macaque activities (Haslam et al., 2013). Uncovering the history of this foraging behaviour opens up opportunities to study its evolution within the macaque lineage and, more broadly, to retrieve comparative data for researchers studying human and primate coastal exploitation.

Long-tailed macaques commonly live near human settlements in Southeast Asia and Singapore is one example of such an interface. In 2011 and 2012, we conducted a census for Singapore’s National Parks Board (NParks), during which we collected behavioral, demographic, and ranging data. We used these data to examine how the presence of humans and access to human food related to changes in the macaques’ time budget, ranging behavior, and group size. We found that human presence was associated with decreased traveling rates, decreased arboreality, increased terrestriality, and increased use of human-made substrates. In particular, access to human food was associated with larger macaque group sizes, decreased arboreality, and increased use of human-made structures. Our results demonstrate how living near humans in an intensely urban habitat impacts macaques. Perhaps with better knowledge of how humans affect urban macaques, we can better plan management strategies to mitigate conflict. We discuss some nonlethal strategies for managing Singapore’s human–macaque interface that could potentially reduce human–macaque conflict. Specifically, we recommend consistent enforcement of an existing feeding ban, the employment of security guards to mitigate conflict in particularly problematic areas, and the expansion of existing education programs for local people and tourists.

Humans and long-tailed macaques (Macaca fascicularis) interface in several locations in Singapore. We investigated six of these interface zones to assess the level of conflict between the two species. We observed macaque-to-human interactions and distributed questionnaires to residents and visitors of nature reserves. We observed an average of two macaque-to-human interactions per hour at the sites, which included affiliative or submissive behaviors (46.9%), aggression (19.1%), taking food and other items (18.5%) searching bins, cars, and houses (13.4%), and nonaggressive contact (2.1%). Two-thirds of interactions occurred when a human was carrying food or food cues, and one-quarter occurred when a human provoked macaques. Only 8% of interactions occurred without a clear human-triggered context. Our interview showed one-third of respondents experienced nuisance problems from macaques. They had items taken from them (50.5%) and received threats (31.9%). Residents reported more nuisance problems than visitors, and their perceptions toward macaques differed. Residents were more aware of the consequences of food provisioning and that there were regulations against feeding. Residents fed macaques less and held more negative sentiments toward macaques. Nearly half of the interviewed people held neutral attitudes toward macaques and only 26.2% of respondents thought conflict with macaques warranted urgent action. Nearly two-thirds of the respondents supported education programs to ameliorate human-macaque conflict, and less than 15% supported removing or eradicating macaques. 87.6% felt that it is importance to conserve and protect macaques. Our results show that human-macaque conflict exists in Singapore, but that it may not be severe. Human behavior is largely responsible for macaque-to-human interactions, and thus could be lessened with management of human behavior in interface zones (i.e. restrict food carrying and provocation). Moreover, our interviews shows people living in Singapore value macaques, do not wish them entirely removed, prefer education-based solutions, and consider conservation and protection of them important.

The long-tailed macaque (Macaca fascicularis) population of the island-state of Singapore consists of ca. 1,218–1,454 individuals. About seventy percent of the population (ca. 1,027 individuals) is concentrated in both Bukit Timah and Central Catchment Nature Reserves, a system of reservoirs and forest reserves located in the center of Singapore. This core population resides mainly along perimeter forest areas of the reserve system, which is bordered by residential and recreational areas (e.g., parks and golf courses) and encircled by expressways. Periphery sub-populations (ca. 427 individuals) persist in forest fragments throughout Singapore mainland and on 5 offshore islands. Much of the Singaporean macaque population overlaps with human settlement and these commensal groups are mainly distributed close to roads, parks and residential areas. At least 70% of these groups are habituated to human presence and at least 50% to food provisioning. Moreover, commensal groups have more individuals and have higher infant:adult female ratios than non-commensal groups. The close association of habituated macaque groups living in human environments has led to increasing human-macaque conflict in Singapore. The overlap is also associated with human-induced population loss resulting from road accidents (2.4%); and trapping efforts (14%) aimed at ameliorating conflict issues. Consequently, it is important to better understand how humans are affecting macaque populations. In order to mitigate human-macaque conflict and at the same maintain a sustainable macaque population in Singapore, there is an urgent need for wildlife management strategies aimed at minimizing the extent of human–macaque conflict. Such strategies should include designing appropriate buffers around reserve areas, revised urban development plans, and managing the behavior of people interfacing with macaques.

In primate sexual relationships, males and females can cooperate through social trade. Market-like trading of sexual activity has been theorized, but no data have yet been presented that clearly show its existence. I collected data to test whether biological market theory could account for exchanges of male-to-female grooming and sexual activity in longtailed macaques. I explored male-to-female grooming, rates of sexual activity, and groomingemating interchanges, which were male-to-female grooming bouts that directly involved mating. Male-to-female grooming mainly occurred when females were sexually active, and males groomed females longer per bout when mating, inspection, or presentation of female hindquarters was involved. Moreover, male-to-female grooming was associated with an increase in female rates for all forms of sexual activity, where in contrast, female-to-male grooming was associated with decreased rates of mating in the groomed males. Males did not preferentially mate with swollen females or invest more grooming in them during groomingemating interchanges, as swellings did not seem to be a reliable indicator of female fertility. Rank status was correlated with grooming payment during groomingemating interchanges in favour of higher-ranked males and females. In support of a biological market interpretation, the amount of grooming a male performed on a female during groomingemating interchanges was related to the current supply of females around the interaction. The results provided evidence of a groomingemating trade that was influenced by a mating market.

Nut-cracking is shared by all non-human primate taxa that are known to habitually use percussive stone tools in the wild: robust capuchins (Sapajus spp.), western chimpanzees (Pan troglodytes verus), and Burmese long-tailed macaques (Macaca fascicularis aurea). Despite opportunistically processing nuts, Burmese long-tailed macaques predominantly use stone tools to process mollusks in coastal environments. Here, we present the first comprehensive survey of sea almond (Terminalia catappa) nut-cracking sites created by macaques. We mapped T. catappa trees and nut-cracking sites that we encountered along the intertidal zone and forest border on the coasts of Piak Nam Yai Island, Thailand. For each nut-cracking site, we measured the physical properties (i.e., size, weight, use-wear) of hammer stones and anvils. We found that T. catappa trees and nut-cracking sites primarily occurred on the western coast facing the open sea, and cracking sites clusters around the trees. We confirmed previous results that nut cracking tools are among the heaviest tools used by long-tailed macaques; however, we found our sample of T. catappa stone tools lighter than a previously collected sea almond sample that, unlike our sample, was collected immediately after use within the intertidal zone. The difference was likely the result of tidal influences on tool-use sites. We also found that tool accumulations above the intertidal region do not resemble those within them, possibly leading to incomplete assessments of macaque stone tools through archaeological techniques that would use these durable sites.

Animal traditions can affect survival by improving how individuals use their environment. They are inherited through social learning and are restricted to small subpopulations. As a result, traditions are rare and their preservation needs to be considered in biodiversity conservation. We studied Burmese long-tailed macaquesMacaca fascicularis aurealiving on Piak Nam Yai Island in Laem Son National Park, Thailand, which maintain a rare stone tool-using tradition for processing hard-shelled invertebrate prey along the island's shores. We found the population had 192 individuals in nine groups and most individuals used stone tools. This population is under pressure from the local human community through the development of farms and release of domestic dogsCanis familiarisonto the island. The level of anthropogenic impact varied in each macaque groups' range and juvenile–infant composition varied with impact. The proportion of young was smaller in groups overlapping farms and was negatively correlated with the amount of dog activity in their range. We also found that coastal use by macaques was negatively related to living near plantations and that the dogs displaced macaques from the shores in 93% of their encounters. We conclude that human impact is negatively affecting Piak Nam Yai's macaques and are concerned this could disrupt the persistence of their stone-use tradition. we discuss the impact and the potential consequences, and we recommend better protection of coastal areas within Laem Son National Park.

We investigated sex differences in how Burmese long-tailed macaques (Macaca fascicularis aurea) used stone tools to open shelled food items along the shores of two islands in Laemson National Park, Thailand. Over a 2-week period in December 2009, we collected scan and focal samples on macaques when they were visible along the shores and mangroves. We found females used stones more often while feeding and used smaller tools than males. Females also processed sessile oysters more than males, whereas males processed unattached foods more than females. It was unclear which sex was overall more proficient at stone tool use, but males did perform significantly better at opening unattached food items with large pounding stones. Females also struck food items more times during tool-use bouts and at a faster rate, but no significant difference was found in average tool-use bout duration. Males processed foods slightly faster within a tool-use bout, but we were unable to detect a significant difference in the rate of food processing while foraging with tools. In summary females chipped open sessile oysters with an axing technique more than males, while males used larger stones to pound open unattached shelled food more often than females. Despite using pounding more than females, males also regularly utilized the axing technique on sessile oysters. Our results are the first assessment of sex differences in macaque stone tool use, providing a basis for comparison with tool use in other primates, and to nonfunctional forms of stone use in other macaques. Am. J. Primatol. 73:1239–1249, 2011. © 2011 Wiley Periodicals, Inc.

Long-tailed macaques are an edge species, preferring to live along the forest borders of many habitat types (Gumert, Chapter 1). The result of this preference is that long-tailed macaques are adaptable generalists that are frequently found along the edges of human settlements across Southeast Asia. Another consequence is that long-tailed macaques can adjust quickly to living with other species, and thus have commonly expanded beyond the edge to overlap with humans in numerous contexts (see Part II). Due to the close association with humans, macaque populations can be powerfully impacted by human activity. In some cases they have been carried and introduced to areas beyond their normal range (see Part III). The overlap of macaques and humans, and the consequences of this overlap, needs to be better understood. While the basis of our relationship with long-tailed macaques is becoming apparent, much more research will be needed to fully understand their population and the causes and consequences of our interface with them. This chapter is an attempt to focus future research in a few important areas that will be necessary for better understanding the population, ecology, and synanthropic nature of long-tailed macaques. This chapter focuses on three subject areas that warrant special consideration for future scientific research on M. fascicularis : population-level research, the issue of ethnophoresy and introduced populations, and the causes and consequences of human-macaque overlap. Directions for population-level research Long-tailed macaques perhaps have the greatest amount of intraspecific variation of any primate species (Fooden, 2006).

It has been long known that females form the stable core of macaque societies (Bernstein and Sharpe 1966; Vandenbergh 1967; Drickamer 1976). They have strong relational ties and develop lifelong relationships with other females in their groups, thus they are considered to be female-bonded (Wrangham 1980). They have particularly close relationships with kin that are characterized by high levels of affiliation (Sade 1965; Drickamer 1976; Kurland 1977; Chapais 1983; Gouzoules and Gouzoules 1987; Kapsalis 2004; Silk 2006). This pattern results because females are philopatric and remain in their natal group for life, while males disperse and emigrate from their natal groups shortly after reaching sexual maturity (van Noordwijk and van Schaik 1985; Pusey and Packer 1987). Since female family lineages generally remain in the same location across generations, macaque groups are based on a cross-generational matrilineal social structure of closely related females. Macaque groups are typically multi-male/multi-female, and consist of several female matrilines (i.e., families), their young, and unrelated immigrant adult males that have migrated from neighboring communities and maintain transient relationships with the females until they emigrate again (de Ruiter and Geffen 1998). Due to the matrilineal structure of macaque societies, females must maintain long-term affiliative relationships with other females in their group. Consequently female cercopithecine primates, such as macaques, are equipped with adaptations for developing and maintaining close female-female bonds because females that can develop larger relationship networks tend to have higher fitness (Silk et al. 2003; Silk 2007).

Burmese long-tailed macaques (Macaca fascicularis aurea) are one of a limited number of wild animal species to use stone tools, with their tool use focused on pounding shelled marine invertebrates foraged from intertidal habitats. These monkeys exhibit two main styles of tool use: axe hammering of oysters, and pound hammering of unattached encased foods. In this study, we examined macroscopic use-wear patterns on a sample of 60 wild macaque stone tools from Piak Nam Yai Island, Thailand, that had been collected following behavioural observation, in order to (i) quantify the wear patterns in terms of the types and distribution of use-damage on the stones, and (ii) develop a Use-Action Index (UAI) to differentiate axe hammers from pound hammers by wear patterns alone. We used the intensity of crushing damage on differing surface zones of the stones, as well as stone weight, to produce a UAI that had 92% concordance when compared to how the stones had been used by macaques, as observed independently prior to collection. Our study is the first to demonstrate that quantitative archaeological use-wear techniques can accurately reconstruct the behavioural histories of non-human primate stone tools.