We recently reported that twin cubs had been born to a captive panda at the Smithsonian National Zoo.

The cubs were nursed separately, swapping between an incubator and the mother, in an attempt to ensure the best possible chance of survival for both newborns. It is common for the smaller and weaker cub to die in panda twins, according to the Smithsonian, due to the mother being unable to cope with the demands of two babies instead of the usual one and natural selection taking its course.

Unfortunately, we now have to report that one of the cubs didn’t make it. The Smithsonian released the following statement:

“The smaller giant panda cub died this afternoon shortly after 2 p.m. More information will be provided at a press conference. The larger cub appears to be strong, robust, behaving normally and is with mother Mei Xiang.”

The tiny, hairless cubs require constant care as they rely on the mother for food, warmth and protection 24/7 until they reach maturity, which isn’t normally until 1-1.5 years of age.

Female pandas are only fertile for 2-3 days a year and usually only successfully rear one cub. This, coupled with loss of habitat and poaching, means the number of giant pandas remaining is extremely low, so the loss of one of the cubs is a saddening blow to conservation efforts of the endangered bear.