BY JONATHAN LERNER

From the January issue of LAM:

The Treetop Trail gives small primates a radically different experience of zoo life. Credit: CLR Design/Arbuckle Industries.

A generation ago zoos were static, passive, and effectively two-dimensional. We were on one side of the window—or fence or moat—and the animals on the other. Depending on how naturalistic or pretty the exhibits happened to be, this formula was more or less dispiriting to both parties. Now a master plan being implemented at the Philadelphia Zoo upends all that; indeed, staffers there call it not a master plan but a “transformation plan.”

It revamps visitor circulation and amenities and addresses stormwater management. But its salient feature is a network of trails throughout the property, including elevated ones that snake through the trees. These let animals travel from the buildings where they live to outdoor exhibit spaces. Different species have access to sections of the trails and the places they lead sequentially, like a time-share. This design strategy, described as animal rotation and flex habitat, has been tried in small iterations at zoos in Atlanta; Louisville, Kentucky; Cleveland; and elsewhere. But Philadelphia’s is the first-ever campus-wide application—“a very big step,” says Jon Coe, FASLA, one of the designers. He explains that the approach rests on understanding that “an animal’s natural territory is not so much an area of land or water, but rather a network of trails connecting key resources.”

Philadelphia’s zoo—the country’s oldest, opened in 1874—has only its original 42 acres. Last spring, its children’s facility was relocated, leaving “a huge part of our usable area open for rethinking,” zoo Chief Operating Officer Andy Baker says. “What if that became a destination for animals that already live at the zoo rather than a new stand-alone exhibit?” An animal traditionally occupies a single location for years, but this “creates a radically different experience by giving them this opportunity to travel and explore.”

Where visitors and animal paths meet, crossings permit closeness and separation. Credit: CLR Design/Arbuckle Industries.

The plan was created by CLR Design, a Philadelphia firm that specializes in zoos, in collaboration with Coe (who is a former CLR principal now living in Australia). It includes three trail types. The Treetop Trail for monkeys and lemurs, opened in 2011, is a flexible 700-foot-long stainless steel mesh tube, held in catenary suspension from poles. It rises as high as 37 feet but also drops close to eye level. At several points it leads into mesh-enclosed “lookouts” encircling sections of large trees. “I initially saw these trails as a way to get the animals into the lookouts,” Baker says, but “they’re treating the trail as real habitat. They sleep in it; they play in it. In the wild, animals similarly have pathways, and they do treat those pathways as usable space.” The Treetop Trail also passes next to a children’s climbing structure of rope webbing, bringing kids and animals eye to eye—and by essentially the same means of locomotion.

Three distinct trail systems will allow animals to roam widely across the campus. Credit: Courtesy Philadelphia Zoo.

To be completed this year is another enclosed trail network, partly elevated and partly at grade, for apes, bears, and big cats. It is also of metal mesh, but given these animals’ greater weight and strength, it is a rigid and more robust system. It incorporates a training platform from which keepers who are interacting with animals can converse with visitors. “That can be more important than just seeing the animal. People want to learn how you take care of them, what they eat, how much they weigh, what are their names,” CLR principal Mark Beauchamp, ASLA, says. A third, fully ground-based trail system will be created for animals like elephants, rhinos, hippos, giraffes, and zebras. Where it crosses visitor paths at grade, drawbridge- or semaphore-like devices will keep people and animals apart, yet quite close. “A keeper can ask a five-year-old kid to come touch the back of a rhino,” Beauchamp says. “Those encounters are quite enriching.”

The zoo intends to conduct cognitive bias studies to test how the new trails affect the animals psychologically. Also in the plans is a systematic evaluation of guests’ reactions. In the meantime, both groups anecdotally seem to enjoy the changes. “The lions, you open the door and they want to know what’s on the other side,” Baker says, though some animals approach the trails more tentatively. “You always think of younger animals as being more plastic, but in fact we’ve seen some of our oldest animals be the first ones to try things out.”

Human animals are responding well, too. “The conversations you hear tend to be very different from [those] at a traditional exhibit. There’s a lot more, ‘I want to be up there,’ identifying with what the animals are doing, and what its purpose is,” Baker says. “I think they imagine themselves using it, particularly the kids.”