He's Armed and Dangerous... and Developing New Stockpiling Tactics!

     Three years ago, a stone-throwing chimpanzee named Santino shocked the research community by providing some of the strongest evidence yet that nonhuman animals consciously plan ahead. Santino, a resident of the Furuvik Zoo in Gävle, Sweden, calmly gathered stones in the mornings and put them into neat piles, apparently saving them to hurl at visitors when the zoo opened. Scientists described his throwing rocks as part of angry and aggressive "dominance displays," (but honestly, if I were on display in a zoo, I might stoop to flicking pebbles at ogling passerby as well. If I were lucky, maybe a  terrorized patron would drop that unfinished smoothie in horror as they left).

     Some factions of the scientific community, however, were not entirely convinced, suspecting that there might be simpler explanations for seemingly humanlike behaviors exhibited by the chimpanzee (immediately, what comes to my mind is whether our own "humanlike behaviors" are not due to some similar "simpler explanation," but I digress...)

     In the new study, primatologist Mathias Osvath primatologist Elin Karvonen report new observations of the rock-hurling primate. Santino's first attempts to throw stones during 2010 came during the zoo's May preseason. As a zoo guide led visitors toward Santino's island compound, the chimpanzee began to engage in a typical dominance display: screeching, standing on two feet, and carrying a stone in his hand. The guide and the visitors retreated before Santino began launching the stones, and then advanced again for a total of three approaches. When the people returned about 3 hours later, Santino advanced toward them, holding two stones, but he did not act aggressively, even picking up an apple from the water surrounding the island and nonchalantly munching on it. But when Santino got within close range, he suddenly threw one of the stones. (It didn't hit anyone.) Haha! Feinting disinterest to strike when they least expect it!

     The next day, Santino was observed pulling a heap of hay from inside his enclosure and placing it on the island close to where the visitors approached. He put several stones under the hay and waited until the group returned about an hour later. Then, without performing a dominance display (sneak attack!) Santino pulled a stone from under the hay and threw it. Later, he pulled a stone that he had apparently hidden behind a log and tried to hit the visitors with that, as well. Over the course of the summer, Osvath and Karvonen observed repeated episodes of this behavior, and also recovered stones that Santino had hidden under hay or logs, racking up 114 days of observation. They recovered a total of 35 "projectiles" that Santino had apparently concealed: 15 under hay heaps, 18 behind logs, and two behind a rock structure on the island.

     The researchers conclude that Santino deliberately engaged in deceptive concealment of the stones, and that this was a new, innovative behavior on his part: Before 2010, Santino had never put stones under hay piles or behind logs. Yes, the tactics must evolve lest your opponents predict your next move! This innovation, the team argues, is further evidence that Santino plans ahead for how he will react to the visitors' approach to his compound, and that this is inconsistent with skeptic interpretations that he cached the stones for some other reason and then just happened to have them at hand when he got mad. By hiding the stones and then trying to deceive zoo visitors into thinking that his intentions were innocent, Osvath and Karvonen argue, Santino was actually anticipating and planning for a future situation rather than simply responding repetitively to a past one.

     The killjoys, however, are still not entirely convinced. The study has been deemed "provocative," but insists that further experiments with more animals are needed before Santino's behavior can be interpreted as true advance planning. Some claim that the authors should have tried additional tests such as putting a hay pile in the compound themselves and seeing if the animal still persisted in carrying hay, or putting the hay piles in unfavorable locations for throwing.

     So there are doubters out there who don't think Santino is plotting against zoo visitors, but is instead engaging in reactive behaviors with no forethought involved. Well, be warned, I tell you. That's just what he wants you to think!