The biggest draw of the primates within any zoo is their expressiveness — we find so many similarities in their facial structure and apparent emotional reactions that they seem to possess more personality than most other animal classes. This is to no small extent misleading, since we have very little in common emotionally, and entirely different motivations and priorities. While it can be very entertaining to observe them, the impressions that we get are almost guaranteed to be inaccurate, often to a huge degree. Yet sometimes the images are still useful in conveying a particular idea anyway.
Here, a pair of Hamadryas baboons (Papio hamadryas) appear to have very strong views about who possesses a particular rock since, you know, they're so hard to come by. The actual confrontation, however, was brief, as are all such interactions with baboons — this is not a species that will be making great contributions to philosophy any time soon, and the delay of the average yellow traffic light would probably be unbearable to them. Though come to think of it, I've felt like flinging poo at traffic lights myself on occasion...
Of course, I can't resist sharing another image which I automatically dubbed as "O face" — if you don't get the reference, it's probably better that way. I'm pretty sure the position isn't actually indicative of anything special; no particular, um, "activity," but then again I could be wrong — after all, look at those clenched toes. And for anyone that wants to relate emotionally, well, okay...
I'm leaving further comments about rocks completely alone.