The Philadelphia Zoo has unveiled a section of new trail and elevated catwalk for orangutans. Eventually, it will connect to the gibbon and gorilla habitats and allow each species to take turns getting out of their usual enclosures.

It's the second phase in a project to connect the whole zoo with a series of animal trails.

Twenty-year-old orangutan Tua was a little skittish at the Thursday grand opening of the trailway when her keeper unlocked her enclosure door and shook a container of peanuts to entice her out.

Eventually, 2 and 1/2-year-old Batu led the way onto the metal walkway, then paused for her mother to join.

Orangutan keeper Maria Schwalbe said the enclosed catwalk will give the primates new territory to stimulate them physically and mentally.

"Orangutans are extremely intelligent animals," Schwalbe said, "so any variety you can introduce into their day is very helpful for them psychologically."

The catwalk passes about 15 feet over a path for humans. Visitors at the opening watched from below as Tua playfully pulled a sheet over her head and hid under it.

This trail is one of three that will eventually connect the whole zoo and allow similar species to wander into one another's enclosures when they are empty. One path is for the smaller primates, one for larger primates, big cats and bears, and the third for rhinos, hippos and giraffes.

Because the larger-hoofed animals don't climb like the other species, that path will be entirely at ground level.

"There might be a day when guests are asked to stop because the giraffes are crossing the path," said Kim Lengel, vice president for animal programs. "So barriers will come down, giraffes will go across, barriers will go back up and you can keep walking."

The Philadelphia Zoo is the first in North America to build such a wide-reaching trail system for such a large variety of animals, according to the Association of Zoos and Aquariums.

Philadelphia Zoo CEO Vik Dewan said the interconnected campus will allow the zoo to make better use of its small footprint.

"So many years people said to us, when are you going to acquire more acreage and become a bigger zoo?" Dewan said. "We've always said, you know, with the natural boundaries that we've had, that's going to be hard to do. But if you took your 42 acres and use the air above it and go into the third dimension and use your trees and find ways for movement to occur, it's an exciting place to be."

Dewan said the primary goal of the project is to provide larger, more stimulating habitats for the animals.

It will also allow people to see the animals in different environments.