(See a photo of an orangutan and baby.)
The animals first learned how to use a suitable tool to gain access to the food in the apparatus. Then the animals were given five minutes to familiarize themselves with a whole series of toolstwo tools that were suitable for getting the food and six that were unsuitable.
After the five minutes, the animals were taken to a waiting room, along with the tools.
One hour later they were allowed to return. To get the food, they had to select a suitable tool and bring it with them.
The apes succeeded in selecting the right tool an average of 7 times in 16 trials.
A second experiment increased the delay to 14 hours, testing one bonobo and one orangutan. While neither ape took suitable tools in the first trial, the orangutan took the right tool in the succeeding 11 tests. The bonobo succeeded in 8 of the following trials.
Tool use is not instinctive in the wild among these animals as nest-building is among birds, for example, Call said.
"There are several studies of bonobos in the wild in which very little tool use has been observed, let alone tool transportation to meet future needs."
In orangutans, he added, "tool use devoted to obtaining food has only been reported in some wild populations, and again, as far as we know, only to meet current needs.
"If tool use is a predisposition in apes, it is clearly of a different sort from nest-building in birds."
Two other similar tests strengthened the authors' conclusion. "Apes selected, transported, and saved a suitable tool," they write, "not because they currently needed it but because they would need it in the future."
Call said that this sort of behavior is not like behaviors in other species that may only look like planning for the future.
"Birds will build their first nest even without having ever experienced the need for a nest to lay the eggs," Call said.
"In contrast, tool transportation in these apes occurs after the need has arisen."
(Read Related Story: "Nut-Cracking Ape May Boost Gorillas' IQ Rep.")
Ape Behavior Questions
Nicola Clayton is a zoologist at England's Cambridge University who has studied how scrub jays hide food for later use. She posed questions about Call's study.
"What of the role of experience?" she said. "Do inexperienced bonobos not save tools for the future? Developmental studies would be very interesting, especially since children don't seem to understand the concept of tomorrow until relatively late."
Call maintains that traditional learning mechanisms and biological predisposition do not explain the results of the experiments with apes.
Some scientists have suggested that skills like those demonstrated by the apes might have emerged in early human ancestors within the last 2 million years, perhaps even as recently as 1.6 million years ago.
But the new results, Call's team says, put the acquisition of planning skills much further back in evolutionary history.
Since both orangutans and bonobos are skilled planners, the authors write, the precursors for planning for the future that we see in humans today may have been present in the great apes as long as 14 million years ago.
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