Stone hammering in natural conditions has been extensively investigated in chimpanzees and bearded capuchins. In contrast, knowledge of stone tool use in wild Old World monkeys has been limited to anecdotal reports, despite having known for over 120 years that Macaca fascicularis aurea use stone tools to process shelled foods from intertidal zones on islands in the Andaman Sea. Our report is the first scientific investigation to look at the stone tools used by these macaques. We observed they were skilled tool users and used stone tools daily. They selected tools with differing qualities for differing food items, and appeared to use at least two types of stone tools. Pounding hammers were used to crush shellfish and nuts on anvils and axe hammers were used to pick or chip at oysters attached to boulders or trees. We found significant physical differences between these two tools. Tools at oyster beds were smaller and exhibited scarring patterns focused more often on the points, whereas tools found at anvils were larger and showed more scarring on the broader surfaces. We also observed grip differences between the two tool types. Lastly, macaques struck targets with axe hammers more rapidly and over a wider range of motion than with pounding hammers. Both our behavioral and lithic data support that axe hammers might be used with greater control and precision than pounding hammers. Hand-sized axe hammers were used for controlled chipping to crack attached oysters, and larger pounding hammers were used to crush nuts and unattached shellfish on anvils. In addition to stones, they also used hand-sized auger shells (Turritella attenuata) as picks to axe attached oysters. Pound hammering appears similar to the stone tools used by chimpanzees and capuchins, but axe hammering has not yet been documented in other nonhuman primates in natural conditions.

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Long-tailed macaques (Macaca fascicularis) feed opportunistically in many habitats. The Burmese subspecies (M. f. aurea) inhabits coastal areas in southwestern Thailand and Myanmar, and some of their populations have adapted lithic customs for processing encased foods in intertidal habitats. We investigated the diet of such macaques in Laemson National Park, Thailand, and identified the variety of foods they processed with stones. We conducted 36 shore surveys to study tool sites following feeding activity, during which we counted the minimum number of individual (MNI) food items found at each site. We identified 47 food species (43 animals and four plants), from 37 genera. We counted 1,991 food items during surveys. Nearly all were mollusks (n = 1,924), with the small remainder primarily consisting of crustaceans and nuts. The two most common foods, rock oysters (Saccostrea cucullata; n = 1,062) and nerite snails (Nerita spp.; n = 538), composed 80.2% of our sample. Four prey species comprised 83.2% of the sample (MNI = 1,656), S. cucullata (n = 1,062), Nerita chamaeleon (n = 419), Thais bitubercularis (n = 95), and Monodonta labio (n = 80). Macaques selected a wide variety of foods. However, they heavily concentrated on those that were abundant, easy to access, and sufficiently sized. The Burmese long-tailed macaque stone-processed diet, which focuses on intertidal marine prey, differs from Sapajus and Pan, who use stones primarily for encased nuts and fruits. In terms of diversity of foods exploited, coastal stone-based predation by macaques resembles the diet of coastal-foraging humans (Homo sapiens sapiens).

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.

Female long-tailed macaques are attracted to infants and frequently groom mothers bearing them. Such grooming often involves the groomer contacting the infant and may be a trade of grooming for infant handling. To identify if grooming and infant handling are directly traded, I collected samples on times after femaleto-mother grooming and on interactions in which a female groomed a mother and contacted her infant. I determined that grooming tended to promote an exchange with infant handling and that the supply of available infants was related to how long a female groomed a mother. Grooming interactions were longer when infants were scarce in the surrounding social environment than when they were abundant, indicating a possible supply-and-demand effect. This supports that grooming may be payment for infant handling. Grooming-infant handling interchanges tended to be unidirectional as mothers usually did not reciprocate grooming. Instead, infant contact occurred. A larger proportion of grooming-infant handling interchanges involved younger infants, but infant age did not seem to influence grooming durations. The length of female-to-mother grooming had no observable effect on handling time. Lower-ranked females groomed higher-ranked mothers and their infants longer than vice versa. Moreover, it was possible to predict up-rank grooming via supply and demand better than down-rank grooming. There was no observable influence of kinship on grooming-infant handling interchange. These results support the conclusion that grooming and infant handling may be traded. Grooming promoted infant handling, while supply and rank predicted the grooming payment a female would offer to access an infant.

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.

Macaca fascicularis aurea (Mfa) is the only macaque which has been recorded to use stone tools to access encased foods. They live in close contact with M. fascicularis fascicularis (Mff) in southwestern Thailand and the hybrids were reported [Fooden, 1995]. Although Mff and Mfa can be seen in the same habitat types, tool-use behavior has never been reported in Mff. Thus, comparing the morphological characteristics and genetics between Mfa and Mff should help elucidate not only the morphological differences and genetic divergence between these subspecies but also potentially the relationship between genetics and their tool use behavior. We surveyed Mfa and Mff in Myanmar and Thailand, ranging from 16° 58' to 7° 12' N. Fecal or blood samples were collected from eight, five, and four populations of Mfa, Mff, and Mff × Mfa morphological hybrids along with three individuals of captive Chinese M. mulatta (Mm), respectively, for mtDNA and Y-chromosome (TSPY and SRY genes) DNA sequence analyses. In addition, eight populations were captured and measured for 38 somatometric dimensions. Comparison of the somatic measurements revealed that Mfa had a statistically significantly shorter tail than Mff (P < 0.05). Based on the mtDNA sequences, Mfa was separated from the Mm/Mff clade. Within the Mfa clade, the mainland Myanmar population was separate from the Mergui Archipelago and Thailand Andaman seacoast populations. All the morphological hybrids had the Mff mtDNA haplotype. Based on the Y-chromosome sequences, the three major clades of Mm/Indochinese Mff, Sundaic Mff, and Mfa were constructed. The hybrid populations grouped either with the Mm/Indochinese Mff or with the Mfa. Regarding the genetic analysis, one subspecies hybrid population in Thailand (KRI) elicited tool use behavior, thus the potential role of genetics in tool use behavior is raised in addition to the environmental force, morphological suitability, and cognitive capability. Am. J. Primatol. 78:441-455, 2016. © 2015 Wiley Periodicals, Inc.

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 materialThe online version of this article (10.1007/s10764-017-9985-6) contains supplementary material, which is available to authorized users.