The AP story about Erie Zoo's shy tiger is showing up in most of the nation's local papers and is plastered all over the internet...just try googling Erie Zoo and tiger! The brief article tells us the tiger, a male named Nikki, who is a recent addition to the zoo, is taking his sweet time to explore the exhibit. Two months, so far, and he's only poked his head out. The article does not go into detail about the exhibit.
After some searching, I've found some additional information related to zoo design. The $500,000 exhibit renovation included adding a yard (essentially doubling the space for the tigers), adding grass versus the traditional rockwork underfoot, and upgrading the visitor experience to include glass viewing for nose-to-nose interaction, mesh training panels, and shade to encourage lingering (and in Erie, I suspect, to protect from snow). Here's a video on the new exhibit.
Nikki came from the Brookfield Zoo, whose tiger exhibit leaves much to be desired. The Brookfield exhibit is a remnant of the historic bear pits, and is mostly rockwork. The Zoo has upgraded as much as possible by adding some natural substrate and encouraging vegetative growth, but the exhibit is highly dated. Visitors can view 180 degrees along the moated pathway. Nikki's hesitation to explore might be exacerbated by the extreme difference in habitats, not to mention his change of city and additional new neighbors. Or, he could, as the AP puts it, just be shy.