Pregnant Tibetan antelope have begun their annual migration to the heart of northwest China's Hoh Xil nature reserve to give birth, the reserve's management bureau said Tuesday.

Around 7:30 p.m. on May 3, about 50 Tibetan antelope went through the Qinghai-Tibet highway to Zonag Lake in Hoh Xil, which is known as the "delivery room" for the Tibetan antelope.

Every year, tens of thousands of pregnant Tibetan antelope migrate to Hoh Xil between the end of May and early June for labor, and leave with their kids in August.

The animal usually mate in December and give birth in late June or early July after a 200-day pregnancy.

The Tibetan antelope is mostly found in Tibet Autonomous Region, Qinghai Province and Xinjiang Uygur Autonomous Region. The rare species is under first-class state protection in China.

The Tibetan antelope population declined sharply from 200,000 to 20,000 due to illegal hunting in the 1980s. The population has recovered thanks to measures taken to improve habitat environment and a ban on illegal hunting.

In July 2017, Hoh Xil became a world heritage site, and is now home to about 60,000 Tibetan antelope.