XINING, May 7 (Xinhua) -- Pregnant Tibetan antelopes have begun their annual migration to the heart of northwest China's Hoh Xil National Nature Reserve to give birth, the reserve's management bureau said Tuesday.

At 10:17 a.m. on Tuesday, the first group of 47 Tibetan antelopes passed the Qinghai-Xizang Highway en route to Zonag Lake, which is at the heart of Hoh Xil.

Protection stations along the migration route will take measures such as temporary traffic control, prohibition on honking and patrolling to ensure the animals reach their breeding spots undisturbed. The reserve's management bureau will also monitor the time, quantity and related conditions of the migration.

Every year, tens of thousands of pregnant Tibetan antelopes start to migrate to Hoh Xil in May to give birth, after mating in November or December, and leave with their offspring around August.

Under first-class state protection in China, the once-endangered species is mostly found in Xizang Autonomous Region, Qinghai Province and Xinjiang Uygur Autonomous Region.

Wu Xiaomin, a Chinese expert on Tibetan antelope protection, attributed the effective protection of wild animals such as Tibetan antelopes and the optimization of Tibetan antelope migration routes to the construction of national parks in recent years.