It’s early summer in Nanhaizi, a wetland park about 15 kilometers south of downtown Beijing. A group of Pere David’s deer are getting ready to select their king.

Stags stir the mud with their antlers, throwing grass and leaves onto their coats to attract does. Before long, they are taunting, chasing, and fighting one another. For these young stags, the battles for dominance go on for almost a month in the wetlands. By mid-June, the stag who prevails — the strongest, or perhaps the luckiest — wins the adoration of the females, who will follow him closely. None of the other stags dare approach the new king or his harem.

In China, this type of deer is known as milu, or sometimes sibuxiang, meaning “four unlike” in Chinese — despite being members of the deer family, Cervidae, these animals are thought to have the head of a horse, tail of a donkey, hooves of a cow, and antlers of a deer.

At Nanhaizi Milu Park, the world’s first nature preserve for milu, the breeding season attracts thousands of tourists eager to see the prospective patriarchs duke it out.

Milu, though endemic to China, became extinct there during the latter part of the 19th century. They were later reintroduced to their homeland in China from the U.K. in 1985.

For those involved in the efforts to reintroduce the animals to China, the results mark a rare success story among China’s wildlife conservation efforts, even if the story is not particularly well-known.

A century ago, the population of milu in the wild was approaching extinction, and only a small group existed in captivity, at the royal hunting grounds of the emperor of the Qing dynasty. Today, these grounds are known as Nanhaizi.

The milu was introduced into Western zoology in 1866 by Armand David, a priest, zoologist, and botanist from France. At that time, the species was completely unknown as a relative of the deer.

Following the discovery of the new species, dozens were sent to zoos and parks in Europe, but only 18 survived in their new environments.

Between 1894 and 1903, Britain’s 11th Duke of Bedford, Herbrand Russell, provided funds to gather all known remaining milu in Europe at Woburn Abbey in Bedfordshire, England.

The duke’s benevolence changed the milu’s destiny. The deer survived, and their numbers increased from 18 to a current population of 220. But the milu in China — their native environment — weren’t so lucky: They died in floods and civil wars during the early 1900s.

According to Maria Boyd, a Slovak-American zoologist, it was the Russell family’s wish to reintroduce milu to China, and they wanted her to do it.

In the early 1980s Boyd studied ecology and animal behavior at Oxford University, where she focused on milu. Her husband is also a friend of Robin Russell, the 14th Duke of Bedford, so she had ample opportunity to observe and learn about the species firsthand.

Boyd began reaching out to Chinese authorities and scientists at the family’s request in the early ’80s. Coincidentally, the Chinese government had also been hoping to bring the milu back.

China’s then Minister of Health Cui Yueli traveled to Britain and visited Woburn Abbey. After Boyd had given him a guided tour of the grounds, Cui agreed to arrange an invitation letter for Boyd to secure a Chinese visa, which at the time was not easily obtainable by foreigners.

Boyd flew to China in 1984. In search of a suitable place for the milu, she toured and inspected a number of possible locations. From fossil evidence she knew that the milu once roamed along the banks of the Yangtze, China’s longest river.

At first Boyd considered reintroducing milu in the Yangtze delta, but after a trip by train to Shanghai, she realized this was not the ideal place she had dreamed of.

“A remote location along the Yangtze River would mean limited on-site support from scientists, veterinarians, and other experts, as well as a long transit time to and from Beijing, where all the official Chinese organizations involved in this project were based,” she told Sixth Tone.

Boyd worked with Chinese expert Wang Song, a zoologist at the Chinese Academy of Sciences, on the project. She and Wang came to the conclusion that Nanhaizi, a wetland home to the last remaining herds of deer in China, would be the perfect location, even though Nanhaizi then was not what it is now. But the idea gained the support of the Chinese government, and soon plans were underway, with waste water and a pig farm being cleared away to make a clean, suitable environment for the deer.

On Aug. 24, 1985, 22 milu arrived in China, and after three months of quarantine, 20 were moved to Nanhaizi, while the remaining two were moved to a zoo. Although some experts worried about whether the animals could survive Beijing’s harsh winters, they soon found that the milu were adapting to their new environments with ease.

“They really took to this place,” Boyd said of the Nanhaizi preserve. She began working on the site, looking after the new arrivals until 1992. While there, she witnessed the first new milu birth in March 1987. At long last, she felt that the animals she had dedicated her life to felt at home.

The success of the Nanhaizi reserve has inspired many of the experts involved in the project. Two years after the opening, a further 18 milu were sent from Woburn Abbey to Nanhaizi.

The Chinese government and local experts soon realized that the Nanhaizi preserve’s proximity to downtown Beijing would limit its expansion and effectively curb milu population growth, so they set up a second reserve — a much larger one with an area of 2,600 hectares, or nearly twice the size of Los Angeles International Airport.

In 1986, following the first reintroduction a year earlier, 39 more milu were appropriated in the U.K. by the World Wildlife Fund and brought to Dafeng, a coastal wetland with a few residents located in eastern Jiangsu province. Three decades later, the reserve had become the world’s biggest milu habitat, with a population in excess of of 3,000 deer — more than half the worldwide population.

For Boyd, her job wasn’t over after the milu populations saw success in Nanhaizi. She kept delaying plans to leave China and finally settled down permanently in Beijing. She worked as a public relations director for hotels in Beijing, but her passion to ensure that the milu of China would survive and thrive remained.

Boyd’s dream for the deer to find their way back into the wild came true in 1991. That year 94 milu in Nanhaizi were relocated to a wetland reserve along the Yangtze, in Shishou, Hubei province. Several years later, after a major flood in 1998, researchers discovered that several milu had escaped from the reserve and were successfully breeding in the wild.

It is estimated that there are between 500 and 600 wild milu in the area now, which is surprising to some experts: It’s rare for endangered animals to rehabilitate their numbers over such short time, and rarer still for them to maintain a stable population in the wild.

On whether this kind of progress is an unprecedented success, Boyd said that the oryx and scarlet macaw had similar stories, but that large-scale rehabilitation generally takes a long time. “In our case,” she added, “it was done within 13 years of the initial release.”

(Header image: A herd of ‘milu’ grazing in the morning sun at the Dafeng Milu Nature Reserve, Jiangsu province, May 11, 2016. Li Dongming for Sixth Tone)