what is Juvenile capuchins are kidnapping infants of another monkey species

There’s a serious case of stranger danger unfolding on an island off the coast of Panama.
 A gang of five juvenile capuchin monkeys living on Jicarón Island has started abducting baby howler monkeys, researchers report May 19 in Current Biology.  This bizarre fad, which has no clear purpose, is often deadly for abductees.
 Capuchins “do such interesting, weird, quirky and sometimes dark things,” says Brendan Barrett, an evolutionary behavioral ecologist at the Max Planck Institute of Animal Behavior in Konstanz, Germany.  These behaviors “can offer a dark window of reflections into what we do.”
 Primates spending time with infants from another species is far less common.  The only recorded example in the wild occurred in 2004, when researchers in Brazil watched female capuchins raise a baby marmoset.
 But “capuchins do all sorts of weird things,” Barrett says.  The Jicarón capuchins (Cebus capucinus imitator) are known innovators.  This island group is the only known capuchins to have invented the use of stone tools.  Still, it was surprising, Barrett says, when a member of his group noticed a young monkey named Joker carrying a howler monkey (Alouatta palliata coibensis) on its back.
 All in all, five male capuchin juveniles abducted 11 howler infants over 15 months.  The babies suffered under capuchin care, with at least four dying during the study period.  Some were as young as a day or two old when taken.  A few capuchins continued to carry the howler corpses around “like puppets or dolls,” Barrett says.  It was sometimes emotionally fraught to parse through the tape.  “Sometimes, you think you’re going to be watching a horror movie.”
 It’s not clear why capuchins have picked up this trend.  There is no evidence that the males ate their infant howlers, even after they died.  Howlers and capuchins don’t compete for the same food, and the infants don’t seem to confer any special status to the carriers.
 Yet the trend is “striking, and also very concerning for this endangered howler population,” Perry says.  It’s also a good example of a non-human primate developing a tradition with no clear purpose, she says.  
 There might be a simple reason why capuchins are abducting babies, Barrett says.  The Jicarón capuchins have no predators and might experience boredom on their island.  Stealing infants might simply be “interesting and stimulating,” he says.  “It makes me wonder what else they’re doing.”