So it appears that chimpanzees recognize other chimpanzees by their behinds, the way humans recognize each other by face. This fact was discovered by real researchers and as noted in the abstract at the link, published in a real scientific journal. Otherwise you would think it was a hoax.
In related news, chimpanzees were compared to college seniors in their ability to recognize the President-elect of the United States, the current cast members of The View, the retiring Minority Leader of the United States Senate, Sean Penn, Michael Moore, Bill O'Reilly, Newt Gingrich, Bill Maher, Kanye West, Al Sharpton, every Comedy Central host and thirty-seven of the known Kardashians. The chimps did better in almost every category except the Kardashians. However, they appeared to be puzzled when viewing the identification photos -- the reason why was eventually determined when one chimp learned enough human sign language to ask why all of these humans were walking upside down.