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They grow up so fast.

The National Zoo today announced several updates to the development of giant panda Mei Xiang‘s surviving cub, who’s now just over three-weeks-old. The cub—a male who still hasn’t been named—has grown to 1.9 pounds (up from 1.3 on Sept. 8) and formed eye slits that will soon open: Giant-panda cubs are blind until six to eight weeks of age. This weekend, “the cub was visible on the panda cams and sleeping for much of the day, which is normal for a cub his age,” the zoo said in a press release. “Keepers noticed that he sleeps with his paw over his eyes, which is a position Tian Tian [the cub’s father] and Bao Bao [his two-year-old sister] frequently sleep in as well.” Like father like son, they say. (Apparently like sister, too.)

Mom, meanwhile, has been leaving the den throughout the day, sometimes for half an hour. On Saturday, “she spent 15 minutes away from the cub, during which time he could be seen on the panda cam scooting around in circles,” the zoo reported. “Keepers noted that the shape of his back saddle, the black marking on a panda’s back, resembles Tian Tian’s.” Mei recently ate a pear for the first time since giving birth—”one of her favorite food items.”

The cub is a twin whose sibling died four days after their birth. As of last week, zookeepers hadn’t completed a final pathology report for the deceased cub, but they suspect it died from “complications associated with aspiration of food material into [its] respiratory system, resulting in the development of pneumonia,” zoo spokesperson Jen Zoon explained in an email to City Desk. The cub weighed 79.8 grams when it died. “There is no precedent for holding a funeral or service at the Zoo, and we will not do so for this cub,” Zoon wrote. “It’s our obligation and duty to collect data and learn as much as possible from this panda cub body to better understand the circumstances surrounding its death and to increase our overall knowledge about the species.”

You can view more photos of the surviving cub—some of him cuddling with Mei Xiang—at the zoo’s #PandaStory Flickr group.

Photo courtesy of National Zoo