Some male Tibetan antelopes look for food at the Hoh Xil Nature Reserve, May 18, 2015. Pregnant Tibetan antelopes have began their annual migration to birthing grounds in the heart of northwest China's Hoh Xil Nature Reserve ten days earlier than normal. Export points out that the early migration may be related to the effect of climate change in the region. [Photo/Xinhua]

A Tibetan antelope looks for food at the Hoh Xil Nature Reserve, May 18, 2015.Pregnant Tibetan antelopes have began their annual migration to birthing grounds in the heart of northwest China's Hoh Xil Nature Reserve ten days earlier than normal. Export points out that the early migration may be related to the effect of climate change in the region.[Photo/Xinhua]

Some Tibetan antelopes head to Chonai Lake, May 16, 2015. Pregnant Tibetan antelopes have began their annual migration to birthing grounds in the heart of northwest China's Hoh Xil Nature Reserve ten days earlier than normal. Export points out that the early migration may be related to the effect of climate change in the region. [Photo/Xinhua]

A Tibetan antelope looks for food at the Hoh Xil Nature Reserve, May 18, 2015.Pregnant Tibetan antelopes have began their annual migration to birthing grounds in the heart of northwest China's Hoh Xil Nature Reserve ten days earlier than normal. Export points out that the early migration may be related to the effect of climate change in the region.[Photo/Xinhua]