The 33-year-old chimpanzee, Santino, has a habit of sneaking up on visitors and hurling stone projectiles at them. Here, he is slowly moving toward visitors, with two projectiles in his left hand. ... more 
The 33-year-old chimpanzee, Santino, has a habit of sneaking up on visitors and hurling stone projectiles at them. Here, he is slowly moving toward visitors, with two projectiles in his left hand. (This image was taken 31 seconds before the thr less 
1 / 26
LiveScience.com | Photo By Tomas Persson, PLoS ONE.
Fri, May 18, 2012 12:30 PM EDT