The newest equine additions to Kazakhstan’s “Golden Steppe” might seem, at first glance, to be unremarkable, with a donkeylike build and a mane that sticks straight up like a zebra’s. But these seven individuals are members of the last remaining species of wild horse: Przewalski’s (pronounced pshuh-val-ski’s) horse, known as kertagy or kerkulan in Kazakh.

Horses roam freely in many parts of the world, such as the Great Plains in the U.S., but these are feral animals, members of a domesticated species that now live in the wild. Przewalski’s horses are a different species entirely—they even have a different number of chromosomes—and this species doesn’t appear to have been domesticated by humans.

“They’re truly wild animals,” says Oliver Ryder, a conservation geneticist who works with Przewalski’s horses at the San Diego Zoo Wildlife Alliance. Once the animals were a crucial piece of the ecosystem in the steppes of Central Asia. But they began disappearing in the 1800s, and by the 1960s, humans and environmental changes had driven them to extinction in the wild. Fortunately, at least a dozen or so horses capable of reproducing survived in captivity, and with carefully managed breeding, the population has made a comeback. This June conservationists reintroduced seven of them to the Golden Steppe of Kazakhstan—the horses were flown to a reintroduction center on the steppe, where they are acclimating to life outside captivity under the watchful eye of conservationists.

Despite living for so long in captivity, Przewalski’s horses haven’t lost their wild streak. “We are not trying to tame them,” says Barbora Dobiášová, ungulate curator at Prague Zoo and head of the European breeding program. “If you enter an enclosure with Przewalski horse herd..., [the stallion] will always try to get between you and the mares” to defend them, she says. The animals need to be sedated in order for the zookeepers to so much as trim their hooves.

On the Golden Steppe, or Kazakhstan’s Altyn Dala State Nature Reserve (altyn dala means “golden steppe” in Kazakh), these horses are once again galloping and grazing, filling the hole they left in the ecosystem, explains Stephanie Ward of the Frankfurt Zoological Society. Ward serves as the international coordinator of the Altyn Dala Conservation Initiative, a conservation partnership with the government of Kazakhstan.

“If you go into the steppe, it’s like you’re in a sea of grass. And at first, it just all looks the same,” she says. But that sea is teeming with life. Birds build their nests in the brush, and burrowing animals tunnel beneath it. Large herbivores such as horses and antelope have historically kept this grass short, which prevented it from drying out and allowed other animals to access the ground beneath, Ward explains. Their dung fertilized the ground, and their grazing promoted carbon sequestration in the soil.

“Grasslands need to be grazed,” Ward says. By the 2000s, however, many of the steppe’s large herbivores were gone or critically endangered. That included not only the Przewalski’s horse but also a wild ass called the kulan and the saiga antelope. “The absence has caused this slow degradation of the ecosystem. The species of plant get fewer and fewer, and they get less and less resilient,” she says.