For a decade, Winky and Wanda were the Detroit Zoo’s only Asian elephants. In the summer months they would kick around in the dirt of their limited outdoor enclosure. During Detroit’s long winters, they were confined indoors, their soft feet rarely leaving the hard concrete.

Then in 2004, during the early stages of a 20-year renovation plan, the Detroit Zoo made a difficult decision that was unusual at the time: Zoo officials decided to give up their prized elephants for the animals’ own good. “The resources we would need to do what elephants would require here just didn’t make sense,” says Scott Carter, the zoo’s chief life sciences officer. Off went Winky and Wanda—two of the zoo’s top attractions–to a wildlife sanctuary in California.

Zoos have come a long way from the unregulated concrete cages typical of early examples of modern zoos, especially as researchers come to understand more about the mental and physical needs of captive animals. Though the Detroit Zoo’s decision to find its elephants a new home is extreme, many zoos today are putting concerns about the well-being and happiness of their animals more front and center than in the past. This is reshaping how zoos are designed and, in some cases, drastically changing how the public views animals and what they experience during their visit.

“We have taken animals into captivity, we are making the decisions they should be making themselves–things like how they get their food and how they spend their time,” Carter says. “And now we are returning some of that decision making to them.”

Being a zoo designer is a job that reaches across fields. Many are trained architects, engineers, or landscape architects, but they are not usually biologists, so they’ll collaborate with keepers, ecologists, and specialists on exhibit designs. They take into account everything from the personality of the individual animals to the “story arc” as a visitor walks through an exhibit. The designers also have to make sure exhibits meet the USDA’s safety and welfare standards, which are required of all institutions that have animals on display, and the more stringent guidelines from the Association of Zoos and Aquariums (AZA), which detail exhibit specifications for accredited zoos and set the tone of modern zoo keeping philosophy. “These projects are very complex, so it helps to be able to apply these different disciplines seamlessly,” says Mario Campos, a partner at Jones & Jones, an architecture firm based in Seattle.

As zoo keeping philosophy changes to focus less exclusively on the experience of visitors, designers are creating new innovations that better suit the animals. They are giving polar bears more control of their environments to echo their natural behaviors, for example, allowing them to forage for their food in a series of drawers. Tigers and wolves are getting more space to roam, and monkeys are now living in troops with just the right number of individuals.

Elephants at the Detroit Zoo ca. 2004 Flickr user The Last Cookie

What’s most important is removing animals’ stressors, but it’s not always easy to tell when an animal isn’t happy, says Julia Hanuliakova, a principal at Zoo Design, Inc. in Seattle. Since zoo animals can’t communicate verbally, keepers monitor their behavior for signs of distress and measure the amount of stress hormones in blood and excrement. Still, it’s hard to pinpoint just why an animal is stressed, and once an exhibit is built, keepers and designers can modify it only so much. Hanuliakova, like many designers, draws heavily upon past exhibit designs for particular species, working with behaviorists, scientists, and keepers to address stressful elements. “We need to make sure that we do better than last time,” she says.