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Chimps engage in stone-throwing pattern, study says

March 3, 2016 Leave a comment

Anyone who has seen chimpanzees in a zoo know that the African primate has a tendency to throw things at people: Rocks, for example, or poop.

Now research shows that Pan troglodytes also likes to throw rocks at trees.

stones under trees - courtesy MPI-EVA, PanAf-Chimbo Foundation

This image shows stones accumulated at the base of an African tree. They were thrown by chimpanzees. Photo courtesy Max Planck Institute, Institute for Evolutionary Anthropology; Pan-African Program: The Cultured Chimpanzee; Chimbo Foundation.

Scientists collected data at 39 sites in four African countries for 14-17 months since 2010. They used non-invasive methods, including camera traps, to demonstrate that chimpanzees engage in a behavior that involves picking up stones near or in a tree and then launching them at the tree.

The behavior is not limited to one or the other gender. The researchers concluded that males most commonly engaged in it, but females also throw rocks at trees. So do juveniles.

It is not clear why chimpanzees throw rocks at trees.

One possibility proposed by the researchers is that it is a form of male dominance display. Another is that it is an expression of chimpanzee culture.

“As the stone accumulation behavior does not seem to be linked to either the abundance of stones or the availability of suitable trees in an area, it is likely that it has some cultural elements,” Christophe Boesch, director of the Department of Primatology at the Max Planck Institute for Evolutionary Anthropology, said.

Chimpanzees are known to use tools such as sticks to extract fish or ants or to remove honey from hives. They also communicate with each other, including by drumming on tree roots and by vocalizing pant hoots.

Pan troglodytes is Homo sapiens‘ closest relative. An individual human’s genome is 99 percent similar to that of a chimpanzee.

Social animals who live in groups that range in size from as few as five to as many as about 150 individuals, chimpanzees are omnivorous. They are known to eat fruit, bark, leaves, and stems, as well as other mammals. Colobus monkeys are a particularly common prey animal for chimpanzees.

Pan troglodytes is an endangered species under American law. Their population is thought to have declined from more than a million at the turn of the twentieth century to as few as about 200,000-300,000 individuals at present, according to FWS.

AP0040-03

Chimpanzees, like the mother and infant pictured here, are humans’ closest living relatives. Flo, the female adult in the image, and her infant Flint were made famous when the primatologist Jane Goodall wrote of her research involving the two chimpanzees. Photo courtesy Jane Goodall Institute.

The new paper appears in the Feb. 29 edition of Nature Scientific Reports.

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Scientists, in first, observe female orangutan kill another female

February 23, 2016 Leave a comment
Bornean orangutan

Bornean orangutans, like their Sumatran cousins, are arboreal and depend primarily on fruit for food. Courtesy Wikimedia.

Orangutans are gentle animals. Among Homo sapiens‘ closest relatives, the arboreal red apes from Asia got their name because the humans who discovered them thought they were “people of the forest.”

They are not immune from a willingness to commit violence. Conflict among male great apes is relatively common and male orangutans will rape females. Among females, fights that cause severe injury or death are unusual.

Now researchers have, for the first time, seen a female orangutan attack and kill another female. She didn’t act alone, either. Her male consort helped.

Orangutans do not live in groups. They tend toward the solitary. But females can have overlapping home territories. In the case described in a recent paper published in the journal Behavioral Ecology and Sociobiology, a young female basically arranged the death of an older female.

The events occurred in 2014. The younger orangutan, named Kondor, and the older orangutan, Sidony, had clashed some years earlier. This time, Kondor enlisted the help of a male named Ekko, who was not yet mature enough to have the characteristic male cheek flanges. Kondor and Ekko copulated near Sidony, then Kondor broke off the sexual encounter and attacked the older female. Ekko prevented Sidony’s escape and also bit her repeatedly. An older male eventually intervened to protect Sidony, but she suffered such extensive injuries that she died two weeks after the fight.

Orangutans are mostly fruit-eaters, though they will also eat bark, leaves, and insects. Their offspring are dependent on parents for a long time. An infant orangutan can be expected to nurse for six years and females stay with their mothers until they are teenagers.

The two species of orangutan – Pongo abelii and Pongo pygmaeus – live on Sumatra and Borneo and are among the most endangered animals on the planet.Their habitat – forest – is under assault by human demand for palm oil and both species are victimized by poaching.

The Orangutan Conservancy estimates that only about 40,000 individuals survive.

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