Certain apes appear to be much smarter than others, with at least one chimpanzee now called "exceptional" when compared to other chimps.
The standout chimp, an adult female in her 20s named Natasha, scored off the charts in a battery of tests. The findings, published in the latest Philosophical Transactions of the Royal Society B, suggest that geniuses exist among non-humans, but that no one attribute constitutes intelligence.
Instead, a perfect storm of abilities seems to come together to create the Einsteins of the animal kingdom. Natasha's keepers at the Ngamba Island chimpanzee sanctuary in Uganda knew she was special even before the latest study.
"The caretakers named Natasha as the smartest chimpanzee, precisely the same chimpanzee that our tests had revealed to be exceptional," study authors Esther Herrmann and Josep Call of the Max Planck Institute for Evolutionary Anthropology wrote.
"All three of the most experienced caretakers included Natasha in their lists (of the most intelligent chimps)," they added.
Natasha has made headlines over the months for her attention-grabbing antics. For instance, she repeatedly escaped her former enclosure, surrounded by an electric fence. She did this by tossing branches at the fence until she didn't see a spark, letting her know that the power was off.
She also learned how to tease humans, beckoning them to throw food her way, only to spray the unsuspecting person with water.
Herrmann and Call decided to study this chimp, along with numerous others, to see if there really are chimp prodigies among non-human great apes. To do this, the researchers created a multi-part mental challenge consisting of eight tasks.
For the first task, the chimps had to find hidden food, testing their spatial knowledge. For the second, the chimps wielded a tool -- avoiding a trap -- to again obtain a food reward. The remaining tasks demonstrated understanding of things like color, size and shape.
"We identified some individuals who consistently scored well across (the) multiple tasks," wrote the authors, who again made note of Natasha, who aced nearly every task.
The researchers could not identify "a general intelligence factor." They instead indicate that ape intelligence might be a bundling of skills related to learning, tool usage, understanding of quantities, and an ability to reach conclusions based on evidence and reasoning.
As the saying goes, necessity may be the mother of invention and, at least in some cases, one reason behind chimp cleverness.
Call, for example, told Discovery News about chimps that make tools for extracting termites out of mounds. The process requires several steps.
"They uproot the stem or use their teeth to clip the stem at the base and then remove the large leaf from the distal end by clipping it with their teeth before transporting the stem to the termite nest, where they complete tool manufacture by modifying the end into a 'paint brush' tip by pulling the stem through their teeth, splitting the probe lengthwise by pulling off strands of fiber, or separating the fibers by biting them," he said.
As for why only some chimps go through such an elaborate process, "a lot depends on the ecological constraints and needs," he said.
In terms of other animals, Herrmann and Call mention the dogs Rico and Chaser, who knew the meaning of hundreds of words.
"Interestingly," the scientists point out, "all of these dogs (considered to be very smart) are border collies. And many of their owners reported that they did not train the dogs to play the fetching game; it was the dogs who trained them!"
The jury is still out on what exactly constitutes such cleverness. The researchers propose that more studies be conducted, with "tasks that capture cognitive, motivational and temperament dimensions."
That's because, in part, a willingness to learn and a positive attitude seem to make as big of a difference in dogs, chimps and other animals as they do in humans.