I got asked that question recently. And as a matter if fact, I have. I did about 70% of all the art assets of the iOS game LAXOPOWER, when I worked over at Unit040. Drawing cow animations and tons of poop was probably the weirdest and most fun assignment I ever got paid for.
It has been a while since I had last visited a zoo. This time I visited the Beekse Bergen safaripark and again I took my sketchbook and supplies with me. It was a bit too cold to draw, but I managed to capture some of the animals on paper.
I love big cats. They know how to keep a pose ;)
For my other zoo animals, search for the 'what I do on holidays' post of 2013