ATLANTA - Ya Lun and Xi Lun, the only giant panda twins in the U.S., of the Atlanta Zoo reached an adorable milestone. The duo just reached began all-day play in their dayroom habitat in the Arthur M. Family Foundation Giant Panda Conservation Center.

The twins have been spending more and more time in the habitat in recent months and now weigh around 22 pounds (Ya Lun) and 21 pounds (Xi Lun).

A rep for the Atlanta Zoo said they are now both very able runners and climbers.

The pandas were born September 3, 2016, the cubs are the sixth and seventh offspring of Lun Lun and Yang Yang. Their older brothers and sisters, Mei Lan, Xi Lan, Po, Mei Lun and Mei Huan, now reside at the Chengdu Research Base of Giant Panda Breeding in China.

Giant pandas represent Zoo Atlanta’s most significant investment in wildlife conservation.

Fewer than 1,900 giant pandas are estimated to remain in the wild in China’s Sichuan, Shaanxi and Gansu provinces. Of these, more than 1,200 live inside nature reserves, eight of which are supported by Zoo Atlanta.

In September 2016, the International Union for the Conservation of Nature (IUCN) downgraded the giant panda’s status from “endangered” to “vulnerable.”

The species remains heavily reliant on conservation programs, and giant pandas face ongoing threats from habitat fragmentation and habitat loss as a result of deforestation and other human activities.

What’s next for pair? Ya Lun and Xi Lun will experience their next milestone – exploring the great outdoors – in coming weeks.