LANZHOU, Aug. 23 (Xinhua) -- A shadow appeared suddenly on the frozen riverbed, no more than 30 meters away. Wildlife photographer Lang Wenrui raised his phone for a closer look, and his heart skipped a beat. The shadow was being cast by a snow leopard.

However, before he could reach for his camera, the animal had vanished, a fleeting encounter in the winter of 2020 that left him regretting the missed shot for years.

Lang, a 50-year-old staffer with the ecology and environment bureau of Su'nan Yugur Autonomous County, northwest China's Gansu Province, has spent more than a decade documenting the wildlife of the Qilian Mountains.

Straddling Gansu and Qinghai provinces, both in northwest China, the Qilian Mountains are a vital ecological barrier and a biodiversity hotspot. According to the Qilian Mountain National Park Natural Museum, the region is home to 402 wild vertebrate species, 1,609 insects, 2,160 higher plants and 506 macro fungi.

Lang, a descendant of herders and well acquainted with the local landscape, has long set himself a goal, namely to record as many species as possible in this vast mountain range.

Over the years, Lang had managed to capture most of these mountains' iconic animals on camera -- except the snow leopard. This animal is under first-class national protection in China and is listed as vulnerable on the International Union for Conservation of Nature Red List of Threatened Species.

Determined to finally photograph what is a slippery customer, he began venturing deep into the mountains whenever the season promised more frequent wildlife activity. Lang carried tents, food and heavy gear into valleys where local herders or rangers had reported sightings of snow leopards -- often waiting there alone for days in his quest for a pic of this species.

"Snow leopards have their own territories and patrol routes, usually along valleys," he explained.

His perseverance was rewarded three years after that first encounter. On the morning of Jan. 7, 2023, after a four-hour trek to the alpine wetlands of Qifeng Township, he spotted a snow leopard walking slowly, with a freshly killed blue sheep at its side.

Holding his breath, he finally captured a snow leopard in sharp detail.

"I was beyond thrilled. It was a dream come true," he recalled.

Lang has now photographed nine snow leopards at various locations in the Qilian Mountains.

In May this year, he even came face to face with one just 10 meters away. He admitted he was "very scared" during the close encounter, and only after a tense standoff did the snow leopard finally retreat into the mountains.

Experts say more frequent sightings of snow leopards reflect a healthier ecosystem in the Qilian Mountains. Notably, improved patrols, satellite monitoring, afforestation and restoration efforts have expanded forest and grassland cover in the area in recent years, improving habitats for local flora and fauna.

Data from the administration of the Qilian Mountain National Nature Reserve in Gansu show that about 300 to 500 snow leopards inhabit the western section of the Qilian Mountains. Since 2018, the ranges of snow leopards, dholes, desert cats and wolves have increased by 9.16, 12.79, 9.79 and 23.46 percent, respectively.

Years in the field have also given Lang insights into animal behavior. He observed that snow leopards raise cubs patiently until they can hunt alone; only once this capability is achieved will they breed again. Also, black-necked cranes return to the same nesting sites each year.

"Wild animals are intelligent and follow their own rules," he said.

So far, Lang has amassed more than 200,000 photos. His mission has grown from simply photographing wildlife to documenting how their habitats are changing over time.

"The task is enormous -- even 20 more years may not be enough," he said. "But I will keep trying." ■