A chimpanzee that famously knocked a flying drone out of the air with a stick earlier this year wasn't reacting out of fear or annoyance but rather executing a pre-planned and deliberate attack. That's according to a new study in Primates. "This episode adds to the indications that chimpanzees engage in forward planning of tool-use acts," researcher Bas Lukkenaar says in a press release. The Christian Science Monitor reports a Dutch TV crew was using the drone to film a documentary on the chimps at the Royal Burgers' Zoo in April. After a test-run with the drone, the chimps started collecting sticks and climbing scaffolding. When the drone returned, a chimp named Tushi was ready, swiping it out of the air with a 6-foot branch.
While studying footage from the busted drone, researchers focused on Tushi's facial expression during the attack, NBC News reports. They found the grimace she makes before and during the incident is similar to what humans do while carrying out a predetermined use of force. According to the press release, the lack of fear in Tushi's expression means she wasn't simply attacking out of reflex. The Monitor explains it's the difference between a calculated plan and swatting at a mosquito. This isn't unusual behavior for the chimps at Burgers' Zoo; they've taught themselves to use 13 different types of tools, the press release states. (Now find out how chimps are more advanced than humans.)