Three thousand years of wild capuchin stone tool use

The human archaeological record changes over time. Finding such change in other animals requires similar evidence, namely, a long-term sequence of material culture. Here, we apply archaeological excavation, dating and analytical techniques to a wild capuchin monkey (Sapajus libidinosus) site in Serra da Capivara National Park, Brazil. We identify monkey stone tools between 2,400 and 3,000 years old and, on the basis of metric and damage patterns, demonstrate that capuchin food processing changed between ~2,400 and 300 years ago, and between ~100 years ago and the present day. We present the first example of long-term tool-use variation outside of the human lineage, and discuss possible mechanisms of extended behavioural change

Robust capuchin tool use cognition in the wild

Most of the studies on primate cognition focus on Catarrhines primates closely related to humans. One alternative primate model for understanding primate cognition is the Platyrrhine capuchin monkey (genus Cebus and Sapajus), which has several convergent traits to hominins. Although capuchins have been targets of cognition studies in laboratories for decades, primates in captivity lack the complete social structures and ecological factors associated with free-ranging environments. Increasing the focus to wild capuchins represents a welcome change to complement captive primate cognition studies in the past decades. Here I do a non-exhaustive review of cognition research on wild robust capuchins (Sapajus), focusing on tool use. Those studies are on the rise and are a source of valuable information to understand primate cognition in natural, evolutionary valid environments, where cognition can be tested and studied in situations similar to those in which those traits evolved

Experimental study of tool use to nutcraking by semifree ranging capuchin monkeys (Cebus apella)

Três experimentos foram realizados sobre o uso de ferramentas para quebra de frutos encapsulados por macacos-prego (Cebus apella) em condição de semi-liberdade no Parque Ecológico do Tietê. O primeiro envolveu a introdução de um nova espécie de coco com o objetivo de estudar a disseminação do uso desse fruto no grupo e os mecanismos de transmissão social envolvidos. Essa disseminação, bastante rápida, em alguns casos deveu-se à aprendizagem inteiramente individual, mas também houve casos de consumo somente após observação de outros indivíduos quebrando cocos ou contato com restos dos cocos. Neste último caso, as eventuais influências sociais estariam restritas ao Realce de Estímulo, mas, onde houve observação direta do comportamento, Emulação ou Imitação não podem ser descartadas. Não foi detectado um padrão definido de preferências na escolha dos indivíduos alvos de observação por coespecíficos em função das características mensuradas dos animais observados. O segundo experimento examinou as preferências na escolha de martelos" de pedra artificialmente produzidos variando de 300g a 1700g, tendo sido encontrada uma preferência pelos dois martelos mais pesados, embora tenha sido observada uma tendência dos juvenis a usar a ferramenta mais próxima, independentemente do peso. O terceiro experimento abordou o transporte das ferramentas, para determinar se este ocorria quando os martelos" potenciais se encontravam a 5m ou 10m do seu local de uso (bigorna"). Os resultados confirmam a ocorrência desse comportamento, o qual, no entanto, foi quase sempre acompanhado do transporte concomitante de cocos.Three experiments were conducted about tool use to nutcracking by capuchin monkey (Cebus apella) at semi-free ranging condition in Tiete Ecological Park. The first involved the introduction of a new species of nut; the aim was to study the dissemination of the use of this new fruit in the group and the involved social transmission mechanism. The quite fast dissemination occurred by individual learning in some cases, but there were instances of consumption only after observation of other monkeys cracking the new nuts or contact with their leftovers.In the latter case, the possible social influences would be restricted to Stimulus Enhacement, but, in the cases where direct behavioral observation took place, Imitation and Emulation cannot be ruled out. There was no correlation between the choice of targets for observation and the measured traits of the targets. The second experiment examined the preferences in the choice of artificial stone hammers ranging from 300g to 1700g. We found a preference for the two heviest hammers, although the juveniles had a tendency to use the nearest tools, independently of weight. The third experiment was about the transport of tools, to determine if the transport of potential tools occurred when these were found at 5m or 10m from the use site (the anvil"). The results confirms the occurrence of this behavior, always involving the simultaneous transport of nuts

Stone Throwing as a Sexual Display in Wild Female Bearded Capuchin Monkeys, <i>Sapajus libidinosus</i>

<div><p>Capuchin monkeys (<i>Sapajus</i> spp.) in captive settings frequently manipulate and throw objects. In the wild, they may push or drop stones and sticks toward targets during inter- or intraspecific threat displays. In addition, female capuchin monkeys exhibit a broad repertoire of behaviors during their proceptive period, including facial expressions, vocalizations, stereotyped body postures, and touch-and-run behavior. This study reports stone throwing as a newly-described communicative behavior during the proceptive display of females in a group of bearded capuchin monkeys (<i>S. libidinosus</i>) in Serra da Capivara National Park, Brazil. During a two-year study, three females from one group were seen throwing stones at males during their proceptive phase. After this period, three other females in the same group exhibited the same behavior. Although it may be possible that this pattern is the result of several independent innovations by each female, the apparent absence of this behavior in other groups leads us to suggest that we have documented the diffusion of a new behavioral trait or tradition within this capuchin social group.</p></div

Throwing events by female capuchin monkeys of PF group after the original research period (01/2012–07/2012).

+<p>Camila Coelho, pers. comm.</p>*<p>Raphael Cardoso, pers. comm.</p><p>These events were recorded during visits to the groups by the authors, or by other researchers working with this group.</p

Stills from video recordings, showing moments of two throwing events.

<p>(a) Pedrita running with a stone just before throwing it at Beiçola;(b) Pedrita picking up a stone, (c, d) running, and (e) throwing the stone at Bochechudo. The video is available as supplementary material - <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079535#pone.0079535.s001" target="_blank">Video S1</a>.</p

Throwing events by capuchin monkey females of PF group.

*<p>Died in 01/2008.</p><p>Hits were considered when the thrown object hit the male before reaching the ground.</p

Vertical bipedal locomotion in wild bearded capuchin monkeys (Sapajus libidinosus)

When carrying objects, nonhuman primates often show bipedal locomotion. Studies of primate bipedality, however, in both nature and captivity, have concentrated on locomotion on horizontal substrates, either terrestrially or arboreally. No observational or experimental study seems to have looked at non-horizontal bipedality, yet we show here that it occurs often in nature in Sapajus libidinosus, the bearded capuchin monkey. The context is transport of small food items from source to site of consumption, in which the monkeys usually carry handfuls of maize kernels over several meters’ distance, both on the ground and in the trees. Most impressively, over a fifth of such bouts are done vertically, when the tree trunk is fully upright. Such vertical bipedality, with or without transport, apparently has not been reported before.</p