There is a reason why the SD zoo is rated one of the best zoo's in the nation... it is huge! We spent the day there (although in fall/winter the day ends at 5pm) and only saw 1/2 the zoo!
the polar bears were way too cool... we actually saw one jump into the water from the under-water observation area. If we could have "felt" the earth shake - we would have... it was the biggest splash I had ever seen.
unfortunately, half way through our zoo time, Gabby began to feel sick. Poor sweetie ended up with a fever and had a crummy night. Luckily, she was much better the next day.