Stone Handling Research Articles

Tool-assisted water scooping in Balinese long-tailed macaques

Abstract While tool use has been widely reported in non-human animals for food acquisition, the use of tools for drinking has been largely overlooked, with primates being a notable exception. We documented tool-assisted water scooping and drinking in several Balinese long-tailed macaques (Macaca fascicularis), living in Ubud, Indonesia, over a period of four years. We observed repeated tool-assisted water scooping using leaves, nuts, pits, and stones. Our results indicate that this behaviour is associated with manual drinking and can be performed in a playful context. This population habitually engages in a cultural form of stone-assisted object play known as stone handling, and it has an overall propensity to manipulate objects in water. We discuss the relationship between instrumental and non-instrumental object-assisted actions, as well as the possibility for this behaviour to be a tradition in this population. This report offers new insights into the limited literature on tool-assisted drinking in monkeys.

Twig-assisted masturbation in Balinese long-tailed macaques

Abstract We documented evidence of idiosyncratic but repeated twig-assisted genital stimulation by Balinese long-tailed macaques (Macaca fascicularis), living in Ubud, Indonesia. This population is known to customarily engage in genital stone-tapping/-rubbing, a behaviour expressed by males and females of different age classes as part of a broader cultural repertoire of stone-directed and overall playful actions known as stone handling. However, genital stimulation using other objects has never been reported in this population and species. We observed repeated and extensive twig-assisted genital stimulation in one adult female and one adult male. We also recorded three instances of twig-assisted genital stimulation in three additional individuals. Our results indicate that this behaviour is not accidental and may be sexually motivated; that is, it may be another form of tool-assisted masturbation in this primate population. This report provides a valuable addition to the increasing literature on tool-assisted behavioural innovations pertaining to self-care and possibly pleasure.

Stone handling in geladas (Theropithecus gelada): implications for spontaneous drawing-like activity as a playful behavior

Stone handling (SH) is a form of solitary object play widely documented in four species of macaques and most recently also in geladas (Theropithecus gelada). Here, we describe the SH activity of two mother-reared captive gelada males, who combined different behavioral patterns in a sequence that occasionally led to the production of colored marks on a hard surface. Two playful techniques of different complexity emerged spontaneously in the two subjects. In the etching and releasing technique, the stone or pieces of it were repeatedly scraped across either a vertical or horizontal hard surface. In the grindandfinger technique, additional patterns were recruited such as scratching the stone to produce small debris that the subjects manipulated through a thumb–index finger precision grip. Animals selected preferentially hard surfaces when their SH sessions involved patterns that potentially released color and engaged in such patterns for longer and in a repeated way. This evidence suggests the high motivation of the two males to engage in drawing-like behavior that, as it occurs for other forms of play, can be characterized by its autotelic self-rewarding nature. Digital video images related to the article are available at http://www.momo-p.com/showdetail-e.php?movieid=momo220922tg01a and http://www.momo-p.com/showdetail-e.php?movieid=momo220923tg01a

Mechanisms of expression of object play: A comparative study of stone handling in two captive groups of long-tailed macaques (Macaca fascicularis fascicularis)

Stone handling (SH) is a form of solitary object play that is socially learned and culturally maintained. We studied two captive groups (Modena, N = 20; Padova, N = 20) of common long-tailed macaques housed in a sanctuary in Italy. Our research goal was two-fold: (1) establish the first SH repertoire in captive-raised long-tailed macaques, and (2) explain major differences in the expression of SH between the two study groups. Despite being of identical size and sharing similar environmental conditions, we found that SH was performed by most group members in Modena, whereas SH was absent in Padova. We aimed to explain this inter-group variation by exploring the role of proximate factors that are known to affect the occurrence of SH: demography, dominance, stone availability, activity budget, and food provisioning. The atypical age structure of Padova (i.e., no immature individuals) may have impaired the emergence of SH in this group. In Modena, we found no significant effect of hierarchical rank on SH frequency and duration and no temporal relationship between SH and feeding. Regarding the activity budget, SH filled in for a portion of affiliative and resting behaviours in Modena. Our findings lend support to the cultural nature of SH.

Dyadic response facilitation of object play in Balinese long-tailed macaques

Social influence is at the core of the emergence and maintenance of behavioral traditions in various animal taxa. Response facilitation is a mechanism of social influence whereby observing a demonstrator performing a behavior temporarily increases the probability that the observer will perform the same behavior. We focused on stone handling (SH) behavior, a form of object-directed play routinely displayed by free-ranging long-tailed macaques (Macaca fascicularis) in Ubud, Bali, Indonesia. We tested whether the expression of SH was subject to dyadic response facilitation. We compared video-recorded focal samples of an individual immediately after they had witnessed a SH bout performed by a conspecific, and matched-control focal samples of the same witness in the absence of any surrounding SH bouts. We found converging evidence that SH was facilitated within pairs of individuals. First, SH occurred significantly more often and lasted significantly longer in the post-witnessing condition than in the matched-control condition. Second, a monkey initiated SH more rapidly in the former than in the latter, and this significant facilitation effect mainly occurred during the first two minutes after witnessing SH. By demonstrating that the expression of SH was socially mediated, we provided further support for the cultural nature of this behavior.

The study on flexible manufacturing system in building decoration stone processing

Abstract Stone materials are widely used in interior and exterior decoration design and public facilities construction. They are one of the essential materials in the construction and decoration field. With the increase in demand of the personality and quality of the decoration materials, intelligent manufacturing of stone processing must be required. With the development of manufacturing technology, especially the rapid development of automatic control technology, CNC machining technology and industrial robot technology, flexible manufacturing technology (FMI) have been used. In the paper an intelligent flexible processing system of stone is designed, which is composed with CNC processing tool, material transmission and storage system, computer control system and stone processing process monitoring system. It can realize fully automatic and intelligent flexible production from building stone processing, stone handling, comprehensive waste treatment, tool optimization and computer control. The calculation method of optimal equipment layout is explained and the field layout of each unit of FMS is given. The purpose of this project is to improve the intelligent level of building decoration stone processing through flexible manufacturing technology and increase production efficiency and material utilization as well as to satisfy needs of diversified product.

Stone affordances as potential for action expression in object play in long-tailed macaques (Macaca fascicularis).

Object affordances play a major role in action expression: (a) providing opportunities to generate potential solutions to instrumental problems and (b) shaping and constraining the motor actions available to an individual. The playful manipulation of objects can facilitate individual acquisition of functional object-assisted actions through affordance learning. We tested the "object affordance" hypothesis in free-ranging long-tailed macaques. This hypothesis holds that the physical properties associated with stone size afford different stone-directed actions, in the context of stone handling (SH) behavior, a form of culturally maintained stone play from which stone tool use can emerge. We predicted that higher SH versatility (i.e., total number of different SH behavioral elements expressed) and higher duration of the SH behavioral element "Pound" would be associated with the manipulation of medium-sized stones, followed by small stones, and then large stones. Our data partly supported these predictions. Both medium-sized and small-sized stones afforded the highest SH versatility, and a higher duration of "Pound" than large stones. As expected, duration of "Pound" was higher with medium than small stones, but the difference was not statistically significant. Our results were consistent with Newell's constraint model, which emphasizes the role of objects' physical properties in limiting and enhancing the expression of actions directed to these objects. The relaxed selective pressures acting on SH behavior may enhance the expression of a range of actions directed toward stones of different sizes that could facilitate the emergence of instrumental solutions and may contribute to explaining the evolution of lithic technology in early humans. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

First evidence of stone handling in geladas: From simple to more complex forms of object play

Stone Handling (SH) is a solitary object play behaviour that can vary from simple exploratory actions to more complex manipulations. So far, among primates, this behaviour has been exclusively reported in macaques. We collected data on 62 geladas (Theropithecus gelada) housed at the NaturZoo (Rheine, Germany). We found that about 70% of subjects belonging to all age- and sex-classes engaged in SH. Due to their exceptional manipulative skills (the highest opposability index among nonhuman primates) and propensity to play, geladas are a good model species to test hypotheses on the function of this form of object play. While the frequency of SH tended to decrease with age of the player, the duration of each session and its complexity tended to increase in juveniles/subadults and adults compared to infants. This age-related variation in terms of frequency, duration and complexity suggests that, in agreement with the motor training hypothesis, SH could have a role in the neural–motor development of immature subjects and a basic function in stimulating neurogenesis and maintaining the psychological well-being of adults. In all age classes, the frequency of SH did not vary across pre-feeding, feeding and non-feeding conditions. Hence, our data do not support the misdirected foraging hypothesis, which predicts that animals engage in SH to anticipate food provisioning. In conclusion, our study reveals, for the first time, the presence of SH outside the genus Macaca and attempts to delineate possible functions of the behaviour in geladas. Since the hypotheses tested cannot be mutually exclusive, long-term studies of SH across individuals’ lifetimes in both captive and wild groups of geladas are needed to clarify the proximate and ultimate functions of the behaviour in this species of Papionini. Finally, long-term studies could also provide some important indications about the cultural nature and social transmission of SH in a taxonomic group outside the Macaca genus.

Comparative Gross Anatomy of the Forelimb Arteries of the Japanese Monkey (Macaca fuscata) and a Comparative Pattern of Forelimb Arterial Distribution in Primates.

Macaca fuscata displays characteristic behaviours, such as stone handling, locomotor behaviour, gait position, and intermittent bipedalism. Differences in characteristic behaviours among primate species/genera could be explained by anatomical details of the body. However, the anatomical details have not been well studied in Macaca fuscata. Arterial models could be one of the anatomical bases for the phylogenetic and functional differences among species, since the arterial supply could be associated with the muscular performance, especially locomotor behaviour. In this study, five thoracic limbs of Macaca fuscata adults were dissected to analyse the vessels. Patterns of arterial distribution in the thoracic limbs of Macaca fuscata were compared with those in other primates. The results indicated that the arterial distribution in the Japanese monkeys was more similar to those in Macaca mulatta and Papio anubis, which is consistent with phylogenetic similarities. However, compared with Papio anubis and other macaques, there were anatomical differences in several points, including (1) the origin of the common, anterior, posterior circumflex, and profunda brachii, and (2) the origins of the collateralis ulnaris artery. The comparative anatomy of the arteries in the forelimb of Macaca fuscata, along with the anatomical studies in other primates, indicated characteristic patterns of brachial artery division and the number of the palmar arches in primates, which is consistent with the phylogenetic division among New World primates, Old World primates, and apes.

Inferring functional patterns of tool use behavior from the temporal structure of object play sequences in a non-human primate species

Inferring functional components of behavioral sequences is a crucial but challenging task. A systematic comparison of their temporal structure is a good starting point, based on the postulate that more functional traits are less structurally variable. We studied stone handling behavior (SH) in Balinese long-tailed macaques, a versatile form of stone-directed play. We tested the hypothesis that stones are used by male monkeys to stimulate their genitals in a sexual context (i.e., “sex toy” hypothesis). Specifically, two SH actions (i.e., “tap-on-groin” (TOG) and “rub-on-groin” (ROG), respectively the repetitive tapping and rubbing of a stone onto the genital area) gained functional properties as self-directed tool-assisted masturbation. Owing to the structural organization of playful activities, we predicted that SH sequences without TOG/ROG would exhibit higher levels of variability, repeatability and exaggeration than SH sequences with TOG/ROG. We also predicted that TOG/ROG would occur more often and last longer in SH sequences in which penile erection – a sexually-motivated physiological response in primates – was observed than in SH sequences in which penile erection was not observed.To identify and compare recurring series of SH patterns otherwise undetectable by using conventional quantitative approaches across SH sequences containing TOG/ROG or not, we used a temporal analysis known as “T-pattern detection and analysis” (TPA). Our predictions about variability, exaggeration and temporal association between TOG/ROG in males and penile erection were supported. As expected, SH sequences without TOG/ROG were, on average, more repeatable than SH sequences with TOG/ROG, but the difference was not statistically significant. Overall, the “sex toy” hypothesis was partly supported, and our results suggested that TOG and ROG are two forms of tool-assisted genital stimulation, possibly derived from the playful handling of stones. These findings are consistent with the view that tool use may evolve in stages from initially non-functional object manipulation, such as object play.

Food Cleaning by Japanese Macaques: Innate, Innovative or Cultural?

Japanese macaques (Macaca fuscata) display a number of cultural behaviours including food washing, stone handling and certain grooming techniques. These are deemed cultural behaviours because it is presumed that they are socially learned and, importantly, that social learning is essential for their emergence. Recently, however, research has revealed that culturally naïve primates can re-innovate presumed cultural behaviours. These behaviours are said to fall within that species’ “zone of latent solutions” (ZLS). A notable cultural behaviour of Japanese macaques is food washing, first reported by Japanese researchers studying wild Japanese macaques in the 1950s. To test whether culturally naïve Japanese macaques would spontaneously wash food and also, therefore, whether food-washing behaviour is within their ZLS, we presented 12 zoo-housed macaques with sweet potato covered in sand near a pool in their exhibit. Over 11 days we recorded the macaques’ behaviour. While 11 of the 12 macaques ate the potato pieces, none washed them. However, 4 macaques cleaned their food, brushing off the sand using their hand or rubbing the potato against their body or another food item, using three distinct techniques. We found no change over time in the rate at which monkeys cleaned or consumed potato, but there was a significant positive correlation between the number of potato pieces a monkey ate and the number of cleaning behaviours performed. We conclude that, minimally, food-cleaning behaviour is within macaques’ ZLS.

Behavior Systems Approach to Object Play: Stone Handling Repertoire as a Measure of Propensity for Complex Foraging and Percussive Tool Use in the Genus Macaca

Behavior Systems Approach to Object Play: Stone Handling Repertoire as a Measure of Propensity for Complex Foraging and Percussive Tool Use in the Genus Macaca

Stone handling, an object play behaviour in macaques: welfare and neurological health implications of a bio-culturally driven tradition

Object play in primates is viewed as generally having no immediate functional purpose, limited for the most part to immature individuals. At the proximate level, the occurrence of object play in immatures is regarded as being intrinsically self-rewarding, with the ultimate function of supporting motoneuronal development and the acquisition of skills necessary to prepare them for survival as adults. Stone handling (SH), a solitary object play behaviour occurs, and has been studied, in multiple free-ranging and captive troops of provisioned Japanese macaques, as well as rhesus and long-tailed macaques for over 35 years now. A review of our combined findings from these observations reveal that infants acquire SH in the first 3-4 months of life and exhibit increasingly more complex and varied behavioural patterns with age. The longitudinal data shows that many individuals maintain this activity throughout life, practicing it under relaxed ecological and social conditions. The ultimate function may be bimodal, promoting motor development in young and neural maintenance and regeneration in adult and aging individuals.

EXPERIMENTAL PRIMATE ARCHAEOLOGY: DETECTING STONE HANDLING BY JAPANESE MACAQUES (MACACA FUSCATA)

Non-human primates using stones in nature provide a rare opportunity to compare directly the behaviour of use with the resulting lithic artifacts. Wild Japanese macaques (Macaca fuscata) customarily do “stone handling” (SH = spontaneous, solitary, non-instrumental and seemingly playful manipulation of stones). Ten populations of monkeys show at least 48 behavioral variants, 13 of which entail repeated stone-on-stone or stone-on-substrate contact that is likely to yield recognizable wear patterns. We collected 10 assemblages of stones after seeing them being used, as well as “control” stones from a nearby hillside. In the first experiment, human subjects of varying degrees of knowledge of SH were asked to separate handled versus non-handled stones. Overall they were unable to do so, but the best-informed subjects were more accurate than the totally naïve ones. In the second experiment, another set of totally naïve subjects was tutored on key points derived from the first experiment. They scored significantly higher, showing that monkey artifacts are distinguishable and that discrimination can be easily taught. Nonhuman as well as human primates have lithic technology, which means that they too have an archaeological record. This complicates prehistory, at least in places in Africa where apes and hominins likely co-existed from the late Miocene onwards. Distinguishing between the hominin “pre-Oldowan” and its ape counterpart industries is a challenge only recently recognized in archaeology. Primate archaeologists tackling these issues in extant species have available not only the standard theory and methods of archaeology but also the behaviour of the makers and users of artifacts. But are non-human primate lithics discernable in the absence of their observed use? If so, then (in principle at least) we may infer multiple archaeological records, even if they coincide in space and time. If not, then our predicament may be compounded, not improved, by the advent of primate archaeology. The aim of the study reported here is simple: to see if stones used by monkeys can be detected, when the only evidence available is the stones themselves.

Stone handling behavior in rhesus macaques (Macaca mulatta), a behavioral propensity for solitary object play shared with Japanese macaques

Stone handling (SH) behavior was systematically studied in a captive troop of rhesus macaques housed at the Primate Research Institute of Kyoto University, and compared with the results of long-term studies of this behavior in Japanese macaques, to evaluate the similarities of SH behavior in these two closely related species. Similar to Japanese macaques, rhesus macaques showed age-related differences in SH. Young animals were more active and displayed more SH patterns and bouts than did adults. Furthermore, the young displayed SH at a higher frequency and their bouts were of a shorter duration, compared to adults. Young adults were more active and displayed more patterns than did older adults. On the other hand, older adults were more conservative and displayed fewer patterns, and engaged in them for longer durations. All individuals displayed SH more frequently in relaxed environmental and social conditions. While lacking an apparent immediate adaptive value, practice of the behavior has been proposed to have long-term functional value for neural and cognitive development in the young and for the maintenance or repair of neuro-pathways in aging macaques that habitually perform the behavior. The results presented here are consistent with what we know about Japanese macaque SH. Given the uniformity of SH behavioral parameters and these two macaque species' close phylogenetic relatedness, we propose that a similar functional and adaptive value for SH can be inferred for rhesus macaques.

Complexity in object manipulation by Japanese macaques (Macaca fuscata): A cross-sectional analysis of manual coordination in stone handling patterns.

Defined as a spontaneous stone-directed noninstrumental manipulative behavior, and comprised of multiple one-handed and (a)symmetrical/(un)coordinated two-handed patterns, stone handling (SH) is a good candidate for the study of complexity in object manipulation. We present a cross-sectional developmental analysis of SH complexity in Japanese macaques (Macaca fuscata), through the combined investigation of bimanuality, coordination, and symmetry in hand use. Bimanual SH patterns were more frequent than unimanual patterns. Among bimanual patterns, coordinated actions were more frequent than uncoordinated ones. We recorded five asymmetrical coordinated SH patterns with manual role differentiation, a form of hand use reminiscent of complex actions involving the use of tools in monkeys and apes. Bimanuality in SH was affected by body posture. Aging individuals performed less bimanual and less coordinated SH patterns than younger individuals. Our result on senescent males performing less bimanual patterns than senescent females was consistent with sex differences found in the late deterioration of complex manual movements in other species. Although some SH patterns represent a high degree of behavioral complexity, our results suggest that SH behavior is not as complex as tool-use or tool-manufacture in other nonhuman primates and hominids.

Supplemental Material for Complexity in Object Manipulation by Japanese Macaques (Macaca fuscata): A Cross-Sectional Analysis of Manual Coordination in Stone Handling Patterns

Supplemental Material for Complexity in Object Manipulation by Japanese Macaques (Macaca fuscata): A Cross-Sectional Analysis of Manual Coordination in Stone Handling Patterns

Principles and levels of laterality in unimanual and bimanual stone handling patterns by Japanese macaques

The preferential use of one hand over the other is considered the primary behavioral expression of structural and functional asymmetry in cerebral structures, which is a decisive factor in human evolution. We present the first analysis of manual laterality in a form of object play—stone handling (SH) behavior—in a free-ranging group of Japanese macaques. Defined as a stone-directed manipulative activity, and comprised of multiple one-handed SH patterns (e.g., grabbing a stone in one hand and cradling it against its chest), as well as coordinated two-handed SH patterns with manual role differentiation (e.g., holding a stone with one hand and rubbing it with the other), SH behavior is a good candidate for the study of hand lateralization. We systematically followed the methodological framework developed by McGrew and Marchant (1997) to measure and analyze the presence, strength, and direction of manual preference in the performance of SH behavior and in various SH patterns, both at the individual and group level. Some individuals showed a significant manual lateral bias on a single SH pattern ( hand preference), whereas others showed consistency in laterality across all or most of the SH patterns they performed ( hand specialization). At the group level, we found that, although their collective distribution of left versus right remained random, most subjects were either significantly but incompletely lateralized, or completely lateralized within particular SH patterns ( pattern specialization), but not across all SH patterns (no handedness for SH behavior as a whole). As predicted by the task-complexity model, hand specialization and handedness were stronger in the coordinated bimanual SH patterns than in the unimanual patterns. We discuss the implications of our findings for the evolution of manual preferences in noninstrumental object manipulation versus stone tool use in nonhuman primates and hominins.

Indirect social influence in the maintenance of the stone-handling tradition in Japanese macaques, Macaca fuscata

Comparative and longitudinal studies have shown that stone-handling (SH) behaviour, defined as the noninstrumental manipulation of stones by performing various behavioural patterns, is socially transmitted across generations as a cultural behaviour in Japanese macaques. We investigated experimentally how stimulus/local enhancement, a form of indirect social influence through the physical traces typically left in the environment by previous stone handlers, might trigger SH behaviour at the individual level, and thus could contribute to the maintenance of the SH tradition at the group level. Through the semicontrolled conditions of field experiments, conducted in the free-ranging provisioned Arashiyama E troop, in which the SH tradition has been well established for nearly three decades, our results supported the stimulus/local enhancement hypothesis. Most group members preferentially directed their SH behaviour towards typical physical traces of SH activity (piles of stones) over randomly scattered stones. Encountering SH artefacts enhanced the use of these particular stones for performing SH in that particular part of the environment. The common occurrence of such ‘play stations’ may favour the frequent reuse of the same stones over time and explain the transport of stones between and around SH artefacts. We provided evidence for the role of indirect social inputs on the long-term persistence of the SH tradition in Japanese macaques, through SH by-products, the stimulating effect of which can be delayed in time and separate in space from others. We discuss our findings from the perspective of socially mediated behaviours, conformity-enforcing responses and niche construction.

Comparison of stone handling behavior in two macaque species: implications for the role of phylogeny and environment in primate cultural variation

This study describes the stone handling (SH) behavior of captive rhesus macaques and compares it with that of a captive troop of Japanese macaques with reference to the relative contributions of phylogeny-driven behavioral propensities, environmental differences and socially facilitated learning to the formation of culture. These systematically collected data demonstrate for the first time that two closely related macaque species might share a common cultural behavior, SH. The rhesus troop displayed SH behavioral patterns that was already described in Japanese macaque troops. The one exception was a new pattern not yet seen in any Japanese macaque troop. Differences in the physical environment of the two study enclosures may be responsible for some of the variation in observed SH behavioral patterns in these two troops. These data support the idea that environmental factors can be important for the formation of cultural variation, when the key materials needed to perform the behavior are present in both habitats (stones). Our results are consistent with the prediction made by Huffman and Hirata [The biology of tradition: Models and evidence. Cambridge: Cambridge University Press. p 267-296] that an interactive triad of phylogenetic, environmental and social factors can be responsible for the formation of cultural variation in primates.