There was once an orangutan named Ken Allen at the San Diego Zoo who was notorious for carrying out complex escape plans. He found every nut and bolt in his cage and unscrewed them; in his open enclosure he threw rocks and feces at visitors. On one occasion, he constructed a ladder out of some fallen branches, carefully testing his weight on the rungs. After that, the zoo raised his enclosure walls and smoothed them to remove handholds.
Hoping to distract Ken, the zoo introduced some female orangutans. But Ken enlisted them as accomplices: While he distracted the zookeepers, his fellow inmate Vicki pried open a window. One time, Ken
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