This new piece from CNN features the unwritten economic laws of some lower-order primates. Turns out monkeys pretty much behave in the same ways we economists would predict--and they do it based on instinct alone.
Reminds me of my Hope College math colleague Tim Pennings and his Welsh Corgie, Elvis. Tim examined whether dogs act as though they know calculus when they play fetch along the West Michigan lakeshore. You can read the paper here, or just check out this video: