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Chimp at war with zoo visitors found even shrewder than thought

May 11, 2012
Courtesy of Lund University
and World Science staff

In his on­go­ing rock-throw­ing war on hu­man vis­i­tors, a chimp at a Swed­ish zoo is re­portedly an­swer­ing his foes’ de­fen­sive tac­tics with sur­pris­ingly clev­er coun­ter­mea­sures of his own.

San­ti­no is ad­just­ing his strat­e­gy in ways that show he can plan ahead, con­ceive the fu­ture be­hav­ior of oth­ers, and con­coct fairly elab­o­rate de­cep­tions, ac­cord­ing to re­search­ers at Lund Uni­vers­ity in Swe­den.

Santino (hold­ing an ap­ple in his mouth) threw the rock that is in his left hand one sec­ond af­ter this cam­era shot. His un­ass­um­ing pos­ture is part of his ela­bor­ate de­cep­tion, re­search­ers say. (Photo: Thom­as Pers­son)


His lat­est tac­tics, they say, in­clude hid­ing his am­mo and sup­press­ing his nat­u­ral urge to adopt scary pos­tures—which, as he has learn­ed, drive back his tar­gets be­fore he can get in a good shot, since they are fore­warned of his dan­ger­ous hobby.

“The find­ings sug­gest that chim­panzees can rep­re­sent the fu­ture be­haviours of oth­ers while those oth­ers are not pre­s­ent, as well as take ac­tions in the cur­rent situa­t­ion to­wards such po­ten­tial fu­ture be­haviours,” wrote the sci­en­tists, Ma­thi­as Os­vath and Elin Kar­vo­nen, re­port­ing their find­ings May 10 in the re­search jour­nal PLoS One on­line.

Previous research by Os­vath de­scribed how the 34-year-old ape pre­pared piles of pro­jec­tiles in ad­vance of human visits. These ob­jects in­cluded both rocks and con­crete mis­siles of his own ma­n­u­fac­ture. The newly pub­lished work de­scribes a fur­ther ev­o­lu­tion in the tech­niques hatched in San­ti­no’s en­clo­sure, at the Fu­ru­vik Zoo north of Stock­holm.

San­ti­no learn­ed to hide his pro­jec­tiles af­ter a rea­liz­ation of his stone-hurl­ing pro­cli­vity prompted zoo guides to re­peat­edly back vis­i­tors away when he started his throw­ing at­tempts, Os­vath and Kar­vo­nen ex­plained. In a re­sponse, San­ti­no took to stash­ing his stones and con­crete chunks in hid­ing places with­in close strik­ing dis­tance of the gawk­ers. The con­ceal­ment sites are both pre-existing struc­tures and piles of hay made by the ape him­self.

Lair of a military master­mind: Santi­no's en­clo­sure from a vis­i­tor's point of view, with points of stra­te­gic in­ter­est marked. The X in the left shows where Santino built his first known hay heap to con­ceal rocks. The left­most ar­row points at a pro­trud­ing rock struc­ture that al­so served as a hid­ing place. The oth­er two ar­rows point at two logs used for  the same pur­pose. (Im­age cour­te­sy PLoS One)


“Both the ma­n­u­fac­ture and use of the con­ceal­ments were likely pre­med­i­tat­ed,” the in­ves­ti­ga­tors wrote. “The be­hav­iour nev­er oc­curred when an­y­one was with­in the chim­panzee’s view, but only af­ter a group had been pre­s­ent and left: i.e., pri­or to their pos­si­ble re­turn.”

San­ti­no al­so learn­ed to in­hib­it his ag­gres­sive pos­tures—or “dom­i­nance dis­plays”—much as peo­ple are ca­pa­ble of do­ing when they’re try­ing to get their way with­out act­ing coun­ter­pro­duct­ive­ly, ac­cord­ing to the re­search­ers. More than once they ob­served him “slowly ap­proach­ing the vis­i­tors, dis­play­ing no ob­vi­ous ag­gres­sive in­tent, be­fore sud­denly throw­ing pro­jec­tiles at them,” they wrote—a contrast to earlier days when he would stomp about, rais­ing his hairs and shriek­ing as his a­ssault got going.

The chim­p’s meth­ods dem­on­strate “co­ordina­t­ion of soph­is­t­icated cog­ni­tive skills to­ward a sin­gle goal,” Os­vath and Kar­vo­nen added. Sci­en­tists have “sug­gested that in hu­mans, fore­sight, mem­o­ry, and the tak­ing of oth­ers’ view­points all seem to be sup­ported by a com­mon brain net­work,” they went on. “The rel­e­vant brain struc­tures ap­pear to be largely shared with chim­panzees.”

San­ti­no is cur­rently ob­serv­ing a sea­son­al lull in the cam­paign­ing: the zoo is only open dur­ing the sum­mer, and he usu­ally stops around the mid­dle of that sea­son anyway, the re­search­ers not­ed. Last year, a hip in­ju­ry side­lined him prem­a­turely from the bat­tle­field, but he has re­cov­ered.


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In his ongoing rock-throwing war on human visitors, a chimp at a Swedish zoo is reportedly answering his foes’ defensive tactics with surprisingly clever countermeasures of his own. Santino is adjusting his strategy in ways that show he can plan ahead, conceive the future behavior of others, and devise fairly elaborate deceptions, according to researchers at Lund University in Sweden. Santino’s latest tactics, they note, include hiding his ammo and suppressing his natural urge to adopt scary postures—which, as he has learned, drive back his targets before he can get in a good shot, since they know about his tendencies by now. “The findings suggest that chimpanzees can represent the future behaviours of others while those others are not present, as well as take actions in the current situation towards such potential future behaviours,” wrote the scientists, Mathias Osvath and Elin Karvonen, reporting their findings May 10 in the research journal PLoS One. Research published in 2009 described how Santino prepares piles of projectiles in advance, both rocks and concrete missiles of his own manufacture. The newly published work describes a further evolution in the techniques hatched in Santino’s enclosure, at the Furuvik Zoo north of Stockholm. Santino learned to hide his projectiles after a spreading awareness of his rock-throwing proclivity prompted zoo guides to repeatedly back visitors away when he started his throwing attempts, Osvath and Karvonen explained. In a response, Santino started stashing his stones and concrete chunks in hiding places within close striking distance of the gawkers. The hiding places are both pre-existing structures and piles of hay made by the chimp himself. “Both the manufacture and use of the concealments were likely premeditated,” the investigators wrote. “The behaviour never occurred when anyone was within the chimpanzee’s view, but only after a group had been present and left: i.e., prior to their possible return.” Santino also learned to inhibit his aggressive postures—or “dominance displays”—much as people are capable of doing when they’re trying to get their way without behaving counterproductively, according to the researchers. They observed him “slowly approaching the visitors, displaying no obvious aggressive intent, before suddenly throwing projectiles at them,” they wrote. The chimp’s methods demonstrate “coordination of sophisticated cognitive skills toward a single goal,” Osvath and Karvonen added. Scientists have “suggested that in humans, foresight, memory, and the taking of others’ viewpoints all seem to be supported by a common brain network,” they went on. “The relevant brain structures appear to be largely shared with chimpanzees.” Santino is currently observing a seasonal lull in the campaigning: the zoo is only open during the summer, and he usually stops around the middle of that season even then, the researchers noted. Last year, a hip injury sidelined him prematurely from the battlefield, but he has recovered.