The National Zoo Built the World's Best Orangutan-Only Rope "Sidewalk"

What happens when you want to give an animal one proper-sized enclosure, but you only have two half-sized enclosures? You need a sidewalk designed for the world’s most arboreal ape.

The National Zoo in Washington DC is best known for its pandas, but if you ask locals what they like most, many will talk about the “O Line.” The O Line was designed in the 1990s, when zoo curators had a problem. They had two places in which they could house new animals, an ape house and an enclosure built around an educational center known as the “Think Tank.” The ape house didn’t have room to grow. The Think Tank had been designated a historic landmark and couldn’t be changed. There was about five hundred feet of ground between the two.


They made lemons into lemonade, by building high towers between the two enclosures and stringing cables along the towers. Each tower got a cage-like enclosure near the top, and each enclosure was lightly electrified. The orangutans could swing along, but climbing down would give them an unpleasant shock. The result was a line that the orangutans could use to get between enclosures whenever they wanted. It’s not entirely secure—three orangutans have decided to climb down off the line and been sedated. However, each “escape” only happened during the ape’s first use of the line, when they got an initial shock, so keepers think they’re less “escapes” and more malfunctions.

There is one other problem with the O Line—one that makes the “lemonade” analogy disturbingly apt.

Yep, the O Line goes over the path that visitors use in the zoo, and some of the orangutans enjoy making the most of it. Fortunately, according the site about the O Line, “The animal care staff respond to any required cleanups. If a visitor is ever hit, the staff are prepared to assist.” Prepare to have orangutan poop cleaned off you by experts.

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