Humans can make some impressive tools, like aerial drones equipped with cameras. But as a troop of chimpanzees at a Dutch zoo recently proved, sometimes even our fanciest technology is no match for a little planning and a big stick.

A video of the encounter, seen above, went viral earlier this year. And according to a new scientific study of the footage, it offers further evidence that chimps not only use tools, but can improvise them quickly and then carry out a strategy for using them.

The incident began when a TV crew was trying to film a documentary about a troop of chimps at Royal Burgers' Zoo in Arnhem, the Netherlands. The crew hoped to get close-up shots by flying a camera-equipped drone over the enclosure, but one of their practice runs (without the camera) had already caught the chimps' attention.

Several chimps grabbed willow branches off the ground, and four carried their sticks as they climbed up scaffolding inside the enclosure. When the crew sent the drone back in to begin filming, it zoomed in on two females named Tushi and Raimee.

Both chimps were seated on the scaffolding and holding their sticks, which the researchers say measured about 1.8 meters (6 feet) long. When the drone flew near Tushi, she took two swipes at it with her stick, hitting it hard enough the second time to crash it. The video shows her grimacing from exertion during the strike, but despite her bared teeth, the researchers say she showed no signs of fear. The camera kept filming as members of the troop then came over to inspect the drone.

It's becoming common for animals to lash out at drones, especially birds of prey — like an eagle that recently downed a drone in Australia. The actions of Tushi and her troop suggest this wasn't just a reflexive attack, however, but a calculated plan involving improvised tools. Humans were widely thought to be the only tool-making animals until a few decades ago, when primatologist Jane Goodall famously observed wild chimps using tools in Tanzania. We now know many species use tools, although scientists are often still surprised by their ingenuity.

"The use of the stick as a weapon in this context was a unique action," says primatologist Jan van Hooff, lead author of the study, in a press release. "It seemed deliberate, given the decision to collect it and carry it to a place where the drone might be attacked." And as co-author Bas Lukkenaar adds, "This episode adds to the indications that chimpanzees engage in forward planning of tool-use acts."

Watch a chimp use a tool to knock down a drone
A female chimpanzee's takedown of a drone offers further evidence of planned tool use, scientists say.