By 3 News online staff
One of the two cubs born to giant panda Mei Xiang at the Smithsonian National Zoo in Washington has died.
Mei Xiang gave birth to the pair just four days ago, but the zoo announced the smaller of the two died after the specialist team saw it wasn't gaining weight and appeared weaker than its sibling.
The smaller cub had been with its mother from about 2pm yesterday until this morning (local time). When the panda team swapped the cubs they saw the possible respiratory issues.
Antibiotics, respiratory support, formula and fluids were given to the cub in an attempt to improve its condition, but their efforts were fruitless.
The cub weighed just 79.8 grams at its time of death.
Zoo pathologists will now perform a necropsy of the cub and the report will provide more information in the next few weeks.
The mortality rate for panda cubs in their first year in human care is 26 percent for males and 20 percent for females.
There is a 50 percent chance giant pandas will give birth to twins, with Mei Xiang's double birth just the third in the US.
The zoo says at the birth of the second cub, Mei Xiang appeared to find it difficult to care for both babies, but didn't show a preference for one over the other.
The team will continue to monitor Mei Xiang and the larger cub via panda cam and they're encouraged by its progress.
They say the cub, which weighs 137.7gm, appears "strong and robust" and is behaving as expected.
However, despite the progress the team will continue to monitor the pair because the cub is still vulnerable and the risk remains high.