Smaller of newborn panda twins dies

Washington

 One of the two giant panda twins born at Washington's Smithsonian National Zoo over the weekend died on Wednesday, turning unexpected joy to tragedy in a matter of days.

 After an ultrasound revealed a possible pregnancy a week ago, zookeepers were greeted with another surprise on Saturday when 17-year-old panda Mei Xiang gave birth to not one, but two baby cubs.

 But the keepers struggled to keep the smaller of the two healthy as Mei Xiang focused her attention on the larger cub.

 The undersize cub - nearly half the weight of the other - passed away on Wednesday, four days after its unexpected birth had made it an Internet sensation.

 "This is a very hard loss for us," zoo director Dennis Kelly told a press conference.

 "It's really hard to keep those little creatures thriving."

 Zookeepers faced an uphill battle after they had trouble convincing Mei Xiang to swap between caring for the smaller and larger cub.

 Tiny, blind, nearly hairless and with little ability to regulate their own body temperature, newborn pandas are completely dependent on their mothers.

 Keepers had stepped into that maternal role by bottle-feeding the cub and administering antibiotics to stave off infections, but their efforts ultimately fell short.

 "After the last swap this morning, we immediately noticed that it appeared weaker, with possible respiratory problems," chief veterinarian Don Neiffer said.

 "We did see some improvements... but things turned and his condition declined. We weren't able to turn things."

 Prior to its death, the cub had stopped gaining weight and was only 79.8 grams (2.8 ounces) when it died, as opposed to the 137.7 grams of its larger sibling.

 Neiffer noted that newborn cubs are extremely fragile and that the cause of death would not be known for sure until an autopsy is performed in the next few weeks.

 But he also said the larger cub was doing very well.

 "We have a very healthy panda. We remain very optimistic about the animal," Neiffer said.

 It is too early to determine the sex of either cub.