Michael Haslam | University of Oxford (original) (raw)

Papers by Michael Haslam

Wild capuchin monkeys (Sapajus libidinosus) at Serra da Capivara National Park, Bra-zil, regularl... more Wild capuchin monkeys (Sapajus libidinosus) at Serra da Capivara National Park, Bra-zil, regularly use stone tools to break open cashew nuts (Anacardium spp.). Here we examine 2 approaches used by the capuchins to position the kidney-shaped cashew nuts on an anvil before striking with a stone tool. Lateral positioning involves placing the nut on its flatter, more stable side, therefore requiring less attention from the monkey during placement. However, the less stable and never previously described arched position, in which the nut is balanced with its curved side uppermost, requires less force to crack the outer shell. We observed cashew nut cracking in a field experimental setting. Only 6 of 20 adults, of both sexes, were observed to deliberately place cashew nuts in an arched position, which may indicate that the technique requires time and experience to learn. We also found that use of the arched position with dry nuts, but not fresh, required, in 63% of the time, an initial processing to remove one of the cashew nut lobes, creating a more stable base for the arch. This relatively rare behaviour appears to have a complex ontogeny, but further studies are required to establish the extent to which social learning is involved.

Nut-cracking is shared by all non-human primate taxa that are known to habitually use percussive ... more 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.

Anthropogenic disturbances have a detrimental impact on the natural world; the vast expansion of ... more 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 Int J Primatol

Animals foraging in their natural environments need to be proficient at recognizing and respondin... more Animals foraging in their natural environments need to be proficient at recognizing and responding to changes in food targets that affect accessibility or pose a risk. Wild bearded capuchin monkeys (Sapajus libidinosus) use stone tools to access a variety of nut species, including otherwise inaccessible foods. This study tests whether wild capuchins from Serra da Capivara National Park in Brazil adjust their tool selection when processing cashew (Anacardium spp.) nuts. During the ripening process of cashew nuts, the amount of caustic defensive substance in the nut mesocarp decreases. We conducted field experiments to test whether capuchins adapt their stone hammer selection to changing properties of the target nut, using stones of different weights and two maturation stages of cashew nuts. The results show that although fresh nuts are easier to crack, capuchin monkeys used larger stone tools to open them, which may help the monkeys avoid contact with the caustic hazard in fresh nuts. We demonstrate that capuchin monkeys are actively able to distinguish between the maturation stages within one nut species, and to adapt their foraging behaviour accordingly. When foraging in their natural environments, animals need to recognize and respond to changes in food targets. This ability is especially useful when dealing with a defensive mechanism of the target food (e.g., toxicity, venom, irritants) where risk of injury represents an important cost for the forager 1. Several animal species have evolved foraging strategies to minimize those potential risks involved when dealing with dangerous prey. For example, meerkats (Suricata suricatta) are able to effectively disarm scorpions to reduce the threat of injury to younger group members 2. Some animals also use foraging strategies that include objects to reduce or prevent the risk of injury involved in consuming challenging food sources. Bottlenose dolphins (Tursiops sp.), for example, use detached marine sponges over their nose to nuzzle for prey in rocky sea grounds 3. Primates have especially been shown to exhibit a variety of solutions as a response to dealing with the defense mechanisms of harmful target foods. White-faced capuchins (Cebus capucinus) wrap naturally-defended caterpillars and fruits in leaves before rubbing them against a substrate, which is suggested to be a means of avoiding noxious substances 4. Chimpanzees (Pan troglodytes) foraging on aggressive army ant nests use nearby trees to reposition themselves off the ground, from where they can more securely dip for the ants below 5. Similarly, chimpanzees are able to minimize risk to accompanying young by predating on aggressive army ants on ant trails rather than at the ant nests, even though feeding at nests yields a higher rate of energetic return 6. Different solutions to minimize painful bites when preying on army ants, including stick tool use, are described for multiple chimpanzee populations throughout Africa 6,7. The observed diversity suggests that hazard avoidance may be a socially influenced response 8. Animal tool use increases net gain by enabling the exploitation of inaccessible or costly to process food resources. This allows access to higher nutritional value foods 9,10 , an adaptive advantage in times of food scarcity 11,12 , competition 13 , or opportunistic foraging 14. Tool size, weight and required transport distance influence the amount of energy expended during a given task 15–17. To maintain the balance between cost and gain, individuals must recognize and manage energy expenditure relative to the task at hand. This requires a comprehension of the functional aspects of the food item, its physical constraints and potential risks involved. Selectivity in the physical properties of tools has been observed amongst different primate species 18–20 as well as corvids 21. Wild chimpanzees adjust their tool selection to changing properties within one target food 22–24. For example, with increasing ripeness of Coula edulis nuts within one fruiting season the nuts become easier to crack and chimpanzees adjust their tool selection accordingly. Neighboring chimpanzee communities that live

Tool use has allowed humans to become one of the most successful species. However, tool-assisted ... more 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.

Stone tool transport leaves long-lasting behavioural evidence in the landscape. However, it remai... more Stone tool transport leaves long-lasting behavioural evidence in the landscape. However, it remains unknown how large-scale patterns of stone distribution emerge through undirected, short-term transport behaviours. One of the longest studied groups of stone-tool-using primates are the chimpanzees of the Taı¨National Park in Ivory Coast, West Africa. Using hammerstones left behind at chimpanzee Panda nut-cracking sites, we tested for a distance-decay effect, in which the weight of material decreases with increasing distance from raw material sources. We found that this effect exists over a range of more than 2 km, despite the fact that observed, short-term tool transport does not appear to involve deliberate movements away from raw material sources. Tools from the millennia-old Noulo site in the Taı¨forest fit the same pattern. The fact that chimpanzees show both complex short-term behavioural planning, and yet produce a landscape-wide pattern over the long term, raises the question of whether similar processes operate within other stone-tool-using primates, including hominins. Where hominin landscapes have discrete material sources, a distance-decay effect, and increasing use of stone materials away from sources, the Taı¨chimpanzees provide a relevant analogy for understanding the formation of those landscapes.

Since its inception, archaeology has traditionally focused exclusively on humans and our direct a... more 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 capu- chin 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.

Mark et al. (2013) recently proposed a new age for the Sumatran Youngest Toba Tuff (YTT) super-er... more Mark et al. (2013) recently proposed a new age for the Sumatran Youngest Toba Tuff (YTT) super-eruption of 75 0.9 ka, based on 40Ar/39Ar dating of proximal and distal tephra deposits. This age falls within previously measured ranges for the eruption (Oppenheimer, 2002; Storey et al., 2012) and is not under dispute here. However, the authors’ interpretation of the palaeoclimatic implications of this finding suffers from fundamental errors.

Archaeologists have used stone transport as a proxy to understand a variety of cognitive, logisti... more 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 (N 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.

We recorded the damage that wild bearded capuchin monkeys (Sapajus libidinosus) caused to a sands... more We recorded the damage that wild bearded capuchin monkeys (Sapajus libidinosus) caused to a sandstone anvil during pounding stone tool use, in an experimental setting. The anvil was undamaged when set up at the Fazenda Boa Vista (FBV) field laboratory in Piauí, Brazil, and subsequently the monkeys indirectly created a series of pits and destroyed the anvil surface by cracking palm nuts on it. We measured the size and rate of pit formation, and recorded when adult and immature monkeys removed loose material from the anvil surface. We found that new pits were formed with approximately every 10 nuts cracked, (corresponding to an average of 38 strikes with a stone tool), and that adult males were the primary initiators of new pit positions on the anvil. Whole nuts were preferentially placed within pits for cracking, and partially-broken nuts outside the established pits. Visible anvil damage was rapid, occurring within a day of the anvil's introduction to the field laboratory. Destruction of the anvil through use has continued for three years since the experiment, resulting in both a pitted surface and a surrounding archaeological debris field that replicate features seen at natural FBV anvils.

Our understanding of the emergence of technology shapes how we view the origins of humanity 1,2. ... more Our understanding of the emergence of technology shapes how we view the origins of humanity 1,2. Sharp-edged stone flakes, struck from larger cores, are the primary evidence for the earliest stone technology 3. Here we show that wild bearded capuchin monkeys (Sapajus libidinosus) in Brazil deliberately break stones, unintentionally producing recurrent, conchoidally fractured, sharp-edged flakes and cores that have the characteristics and morphology of intentionally produced hominin tools. The production of archaeologically visible cores and flakes is therefore no longer unique to the human lineage, providing a comparative perspective on the emergence of lithic technology. This discovery adds an additional dimension to interpretations of the human Palaeolithic record, the possible function of early stone tools, and the cognitive requirements for the emergence of stone flaking. Palaeoanthropologists use the distinctive characteristics of flaked stone tools both to distinguish them from naturally broken stones and to interpret the behaviour of the hominins that produced them 4 .

We report the first observation of probe tool use by a wild adult female bearded capuchin (Sapaju... more We report the first observation of probe tool use by a wild adult female bearded capuchin (Sapajus libidnio-sus), at Serra da Capivara National Park (SCNP), Brazil. This individual used several stick tools and one grass stem to probe her nostrils, usually triggering a sneeze reaction, and also used stick tools to probe her teeth or gum. Both of these behaviours were accompanied by inspection and licking of the tool following use. We have termed these self-directed actions nasal probe and toothpick, and neither has been previously reported in wild capuchins. While stick tool use is common among foraging male capuchins at SCNP, the novel and at present idiosyncratic activities performed by the female monkey add to the known behavioural repertoire for this species.

Primates; journal of primatology, Jan 26, 2016

Complex food-processing techniques by gorillas, chimpanzees, and orangutans have allowed comparis... more Complex food-processing techniques by gorillas, chimpanzees, and orangutans have allowed comparisons of complex hierarchical cognition between great apes and humans. Here, we analyse preliminary observations of free-ranging long-tailed macaques (Macaca fascicularis) (n = 3) in Thailand processing Opuntia sp. cactus fruits. From our observations, we suggest that there is potential to extend the analyses of hierarchical cognition to Old World monkeys. We found that the macaques used six behavioural sequences to obtain Opuntia fruits, remove irritant hairs from the skin of the fruits, and break open, and consume the fruits, each a unique combination of 17 action elements. Removing irritant hairs involved abrading fruits on a sand or rock substrate, and washing fruit in water. The behavioural sequences that macaques use to process Opuntia potentially show features of hierarchical organisation described in the leaf-processing behaviours of great apes. Our observations highlight the need ...

The concept of extended or distributed cognition has been present in archaeology for some time, y... more The concept of extended or distributed cognition has been present in archaeology for some time, yet despite its inclusion of non-human hominin ancestors, it has remained distinctly anthropocentric in nature. Here, we suggest that the same concept may also be used to independently describe and interpret non-human animals within their own social and material networks. We illustrate this suggestion with examples from the tool use behaviour of wild monkeys and chimpanzees. Non-human primate social groups develop bodies of traditional knowledge, and we consider whether idiosyncratic expression of such knowledge may be viewed in terms of an individual's constructed social identity. At a micro-level, the performance of an individual tool use technique may be analogous to the idea of 'personhood' found in anthropological holistic or perspectivist theory; at a macro-level the physical and social distribution of primate technology is amenable to interpretation as an example of extended or distributed cognition. We conclude that combined consideration of extended cognition and niche construction offers a promising means for interpreting the material residues of non-human primate behaviour.

Primates; journal of primatology, Jan 26, 2016