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201807Jul18:00

First report of habit­ual stone tool use by a fourth pri­mate genus — Cebus monkeys

Infor­ma­tion
pub­lished 07 July 2018 | mod­i­fied 08 July 2018

White-​faced capuchin mon­keys in Panama’s Coiba National Park habit­u­ally use hammer-​and-​anvil stones to break her­mit crab shells, snail shells, coconuts and other food items, accord­ing to vis­it­ing sci­en­tists at the Smith­son­ian Trop­i­cal Research Insti­tute (STRI). This is the first report of habit­ual stone-​tool use by Cebus monkeys.

white faced capuchin monkey tool useA male capuchin mon­key uses a stone to break open seeds of an indian almond tree, Ter­mi­na­lia cat­appa. This tree species is com­mon on beaches around the world.
Image Credit: Bren­dan Barrett

Despite being stud­ied for more than 25 years at sev­eral field sites, no species in the genus Cebus has ever been pre­vi­ously observed habit­u­ally using stone tools,” said lead author Bren­dan Bar­rett, for­merly a short-​term fel­low at STRI, and now a post­doc­toral researcher at the Max Planck Insti­tute for Ornithol­ogy and the Max Planck Insti­tute for Evo­lu­tion­ary Anthro­pol­ogy. The results of the study is pub­lished on 20 June on preprint server bioRxiv and have not been peer-​reviewed yet.

To observe white-​faced capuchin mon­keys (Cebus capuci­nus), Bar­rett and col­leagues set up motion sensor-​triggered cam­era traps. Based on a year of data from the cam­eras, researchers never saw adult females using stone tools, despite their pres­ence at the site. Among males, stone-​tool use was com­mon. At one site, capuchin mon­keys used tools on more than 80 per­cent of the days they were observed.

Coiba National Park lies about 23 kilo­me­ters from Panama’s Pacific Coast and con­sists of nine larger islands and more than 100 smaller islands. The islands were iso­lated from the main­land between 12,000 and 18,000 years ago by sea-​level rise after the last ice age. Cebus mon­keys are found on three of the larger islands, Coiba Island (50,314 hectares), Jicarón Island (2,002 hectares) and Ranchería Island (222 hectares). Stone tool use was only observed on Jicarón Island.

White-​faced capuchin stone tool use in Coiba National Park, Panama


(Source: Bren­dan Bar­rett YouTube channel)

Capuchins used large stones held in both hands to process tough Ter­mi­na­lia cat­appa nuts, and smaller stones held in one hand to process smaller items such as her­mit crabs and snails. They also trans­ported seeds and stones to pro­cess­ing areas.

Researchers con­cluded that tool-​users spend a large amount of time on the ground, which is pos­si­ble on this pro­tected island where the mon­keys have few preda­tors and resources are likely to be as or more scarce than they are on the main­land. Cebus mon­keys on the main­land do not use stone tools, although they com­monly pound and rub fruit and small-​animal prey such as squir­rels and lizards on branches to process them as food.

Species in the genus Sapa­jus, known as robust capuchin mon­keys, native to South Amer­ica, have long been known to use tools. In fact, tool use is one of the char­ac­ter­is­tics that dis­tin­guishes this group from the smaller mon­keys in the genus Cebus, known as gracile capuchins, found in Cen­tral and South America.

Chim­panzees (Pan) and macaques (Macaca) also use stone tools. Tool use in macaques is also lim­ited to islands. The use of stone tools by robust capuchins, gracile capuchins in the Amer­i­cas and macaques in Thai­land to process T. cat­appa nuts will be an inter­est­ing oppor­tu­nity to com­pare the ori­gins of this behav­iour. Tool use in other pri­mates likely pre­ceded tool use by the first human rel­a­tives roughly 3 mil­lion years ago.

In addi­tion to the excite­ment of adding a fourth (known) genus of stone-​tool-​using pri­mate to our list, it is excit­ing to be doing eco­log­i­cal research in Panama’s Coiba National Park, a unique place where there is a lot of poten­tial for dis­cov­ery for con­ser­va­tion research to be done,” Bar­rett said. “STRI’s new Coibita field sta­tion helps make it pos­si­ble to do field research on Jicarón and Coiba Islands, remote places where research is logis­ti­cally challenging.”

The capuchins of Coiba National Park pro­vide us with an amaz­ing oppor­tu­nity for study­ing how and why stone-​tool use emerges, as well as what record it leaves behind.

Mar­garet C Cro­foot, research asso­ciate at STRI and pro­fes­sor of anthro­pol­ogy at the Uni­ver­sity of Cal­i­for­nia, Davis.

White-​faced capuchins are a very well-​studied species, so stum­bling upon a tool-​using pop­u­la­tion – the only one known for the entire genus – was really unex­pected and serves as an impor­tant reminder of the behav­ioural diver­sity wait­ing to be dis­cov­ered. It high­lights the impor­tance of remote and little-​known areas like Coiba National Park, and serves as a vivid call to action to con­serve behav­ioural, cul­tural and genetic diver­sity,” Cro­foot added.

(Source: The Smith­son­ian Insti­tu­tion news release, 03.07.2018)


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