At 4 ½ months old, the San Diego Zoo's newest giant panda, Xiao Liwu, is growing into a rambunctious cub.
During his weekly exam Thursday (Dec. 13), the baby bear weighed in at 14 pounds (6.3 kilograms) and was very active, making it difficult for zookeepers to take measurements.
"It might be the terrible toddler stage," Tracy Clippinger, a veterinarian at the zoo, said in a video, "but it's great to see because he's becoming his own little panda."
That's a change from earlier this month when the little guy dozed off during his exam, though staff were able to get a good look at the cub before his nap, counting eight teeth in his mouth, with evidence that more were ready to break through the gums.
To test Xiao Liwu's development this week, Clippinger checked that his back legs would continue moving forward if she held his front legs off the ground and vice versa. She also tested how well his eyes followed her finger as she passed it in front of his face, according to a statement from the zoo.
Xiao Liwu, whose name means "Little Gift," was the sixth cub born to the zoo's panda mom Bai Yun. All the San Diego Zoo giant pandas are on a research loan from China, the only place where the species still exists in the wild. Four of Xiao Liwu's siblings have already been moved out of California to join the Chinese panda conservation and breeding program.
Captive breeding is an important way to study and conserve the endangered species, as just 1,600 giant pandas are thought to be left in the wild. In addition to habitat loss from human activities and low reproductive rates, giant pandas' survival is also threatened by climate change. A study released in the journal Nature Climate Change in November found that global warming could wipe out much of the bears' chief food source, bamboo, over the next century.
Follow LiveScience on Twitter. We're also on &.