(AP) The Philadelphia Zoo is letting some animals take a walk on the wild side sort of.
A set of enclosed trails allows certain species to leave their exhibits and travel throughout the zoo.
Zoo officials say the protected pathways are designed to enrich the animals' lives by giving them the ability to explore and see and smell new things.
They say the network also enhances the visitor experience because zoo-goers may see creatures in unexpected places, such as in the trees.
The zoo last week opened the Great Ape Trail, which permits orangutans to roam along an overhead walkway. Small monkeys and lemurs have used the Treetop Trail for about a year.
Curators also plan to study the animals' reactions to the trails.