A couple dozen steps. Two fistfuls of tomatoes. A perfectly upright posture.
That was all it took to launch Louis, an 18-year-old male western lowland gorilla at the Philadelphia Zoo, to viral fame.
It started in early March, when zookeepers filmed Louis standing on two legs, like a human, strutting from one side of his enclosure to another. In his hands, he clutched a few small, red-orange blobs.
They were tomatoes, the zoo explained later. A special treat for him.
In the caption for the eight-second video (titled "Snacking on the Run"), the zoo explained that, although it isn't common for gorillas to walk on two legs, Louis had made a habit out of doing so regularly.
"He can often be seen walking bipedally when his hands are full of snacks or when the ground is muddy (so he doesn't get his hands dirty)!" the zoo wrote.
In a post-Harambe world, of course, people have thoughts whenever a western lowland gorilla goes viral. Video of Louis's brief stroll quickly spread across the internet, and the public questions flowed from there: Did Louis have obsessive-compulsive disorder? Was there something secretly wrong with his two front legs?
Reactions alternated between charmed ("I also walk upright when my hands are full of snack," one Facebook commenter wrote) and oddly accusatory ("APE-ING AROUND: This gorilla strolls around like a HUMAN to avoid getting his hands - or his food - dirty," blared the Sun, a British tabloid).
The reality, zookeepers say, is not so dramatic, but no less endearing.
Louis is "fully healthy, 470 lbs. of solid muscle" and his "hands and feet and legs work very well," said Michael Stern, curator of primates and small mammals at the Philadelphia Zoo.
He simply is exhibiting behaviour that, although "pretty rare," does manifest from time to time in gorillas.
"They will walk upright when they're playing with each other or they're displaying to try to look big and strong . . . or to wade into a swamp," Stern told The Washington Post.
The difference is that, while other gorillas might walk upright "for a few seconds or a few steps," Louis can mosey around on his hind legs for an extended period - and, in fact, seems to prefer to, especially when it comes to protecting his snacks.
"He actually does it more often than you might think," Stern said. "It depends on the situation. If the ground is really muddy, he will do it more often. If he's getting fed some treats, like tomatoes, that might squish more, then he tends to walk upright with things like that."
The idea that Louis is a clean freak is "a little anthropomorphic," but it is true that he avoids the mud as much as possible, Stern said. For instance, there is an area in the enclosure that tends to form a puddle when it rains; it doesn't seem to bother the zoo's six other gorillas, but Louis always avoids it, he said.
"It may be he doesn't like the feel of it on his skin [rather than wanting to keep his hands clean], but he does seem to not want to get his hands muddy," Stern said. "They come from the rain forest, so you'd think they would be used to it. But for whatever reason, his particular personality, he really does not like to get his hands muddy."
Louis was born at the St. Louis Zoo but moved to the Philadelphia Zoo in 2004, and Stern said zookeepers there have been aware of Louis's quirks for some time. His upright jaunt caught on camera in early March probably had to do with two things: His diet and the presence of 16-year-old Kuchimba, the zoo's other "bachelor male" western lowland gorilla.
Gorillas there eat many small meals throughout the day - mostly hay, branches and leafy green vegetables, but very occasionally also fruit, Stern said. To mimic the natural foraging the animals would do in the wild, zookeepers tend to scatter the food all around the yard.
"If it's something really tasty, like the tomatoes, Louis will go around collecting them so that Kuchimba, the other guy, doesn't steal what he thinks belongs to him," Stern said.
Since the zoo posted the video of Louis, it has been viewed and shared tens of thousands of times. Stern said there have since been people who have visited the zoo after watching the video, specifically hoping to get a glimpse of Louis walking upright - and, to their delight, he has obliged.
Stern said he can understand why the video has gone viral but hopes the awareness extends beyond the eight-second clip. Since 2007, the International Union for Conservation of Nature has listed the western lowland gorilla as "critically endangered," noting that the population of the species has declined by more than 60 percent in 25 years.
"All the gorillas have their different personalities," Stern said. "We really hope that by getting to know him that way, hopefully that gets more people's hearts and minds thinking about what they can do to help protect a critical endangered species."