A forest ranger in Sichuan Province has recorded rare video of courtship among wild giant pandas.

A female panda sits in a tree while a number of males can be heard roaring at her in the two clips captured by Yang Jihong in the Wolong National Nature Reserve on Sunday.

The panda remained in the tree for an hour but rushed away when Yang approached.

Male pandas track female pandas in heat from their urine and squeaking. When they find her, males will compete to impress the female and hopefully win the right to mate with her. Only one will succeed, explained Huang Yan, deputy chief researcher with the China Conservation and Research Center for the Giant Panda.

Staff at Wolong are collecting pandas' excrement for DNA tests to identify how many males participated in the courtship.

"Generally speaking, pandas enter their annual estrus cycles during the period from March to May. For female pandas, their estrus can last about a month but their ovulatory period only lasts one to two days," Huang said.

If the female panda is reluctant, the mating fails, even during estrus.

The giant panda lives mainly in the mountains of western provinces of Sichuan, Shaanxi and Gansu. They are threatened by habitat loss and a very low birthrate.

Sichuan was home to 1,387 wild giant pandas at the end of 2013, accounting for almost 75 percent of the total across the nation.

Giant pandas have a low fertility rate because they are sexually inactive. Female pandas become pregnant only once a year and deliver at most three cubs.