How does one man single-handedly keep several young men in close proximity, while meandering through a zoo?

Oh, you need to know your wildlife.  Tour the zoo between meals and carry a large bag of popcorn.  No need to keep track of the kids.  Trust me, they’ll find you.  They’ll keep coming back for more.

Unfortunately, bears also like popcorn.  Darn that Law of Unintended Consequences.