Any new parent will tell you that babies are exhausting. But recent research out of China shows that endangered giant pandas are so tired they are choosing not to have more babies. Pandas are known to be notoriously slow breeders. However, their progress has slowed even more in the past year, and scientists say their energy-draining current offspring are the cause. 

Giant pandas are considered to be among the world’s most endangered animals. There are fewer than 3,000 still in the wild, and they can live up to the age of 30.

In 2008, 18 baby pandas were born at the Chengdu Giant Panda Research Institute in Sichuan Province. This center is home to 83 giant pandas, about a third of the total pandas kept in captivity in China. But in 2009, the tired mothers could manage only four. 

This includes twins born to panda Li Li on July 19. Panda twins Wen Li and Ya Li have been keeping Li Li on her panda toes. Apparently, naughty Wen Li has made repeated attempts to escape from the wooden pen where she is kept. This is in part why researchers have concluded that the tired moms are too exhausted to conceive more cubs. 

Baby panda Ya Li is considered better behaved than her sister. No word on if Ya Li’s more demure personality can help convince her maternal family that another brother or sister is a good idea.