This is an interesting article that scientist, Dr. Wang Dajun, provides us with some insight.
He did an interview with the Huffington Post concerning the topic concerning the size of panda cubs and they also included a video of Dr. Dajun with a playful youngster that joined him while doing his work in the mountains back in 1996.
The Huffington Post | By Arin Greenwood Posted: 08/31/2013 2:38 pm EDT | Updated: 08/31/2013 11:00 pm EDT
The panda baby born at the National Zoo in Washington just over a week ago was pink, wriggly and almost impossibly small -- about a third of a pound at its first checkup. This tiny creature's mother, Mei Xiang, weighs more than 230 pounds.
Pandas are considered to be "endangered," with about 1,600 in the wild and another few hundred in captivity (some estimate there are more like 3,000 pandas in the wild). Their low birth rates, males' reluctance to mate in captivity (keepers have even tried panda porn to get them in the mood) and high mortality rates (about a quarter of males and a fifth of females die in their first year, by some accounts; others put the figure higher) aren't helping.
Traditionally, baby pandas aren't even named until they are 100 days old. These creatures can face demise during their early lives in what seems like countless ways. In Washington in 2012, Mei Xiang gave birth to a cub, which died after 6 days from liver and lung problems.In Tokyo, where a 6-day-old cub died from pneumonia after its mother's milk got in its airway, officials said that 60 to 70 percent of newborn pandas die within their first week -- sometimes by being crushed by their mothers.
Here's Conservation International's description of what can befall the rare and delicate newborns: At birth, a panda cub is helpless. It takes considerable effort on the mother’s part to raise it. A newborn weighs three to five ounces. Pink, hairless, and blind, the cub is 1/900th the size of its mother.
Except for a marsupial (such as the kangaroo or opossum), panda babies are the smallest newborn mammals relative to their mother's size. Cubs don’t open their eyes until they are six to eight weeks of age, and are immobile until three months. A cub may nurse for up to nine months before it can eat bamboo.
A cub is nutritionally weaned at one year, but not socially weaned for up to two years. Infant mortality is lower in the wild than in captivity, estimated at around 40 percent. The perilous nature of being born so tiny raises one big question:
Why are panda newborns so small? Because of bamboo, said wildlife biologist Dajun Wang, who has not only studied wild pandas in China but also has a video of himself with a panda youngster in the wild on YouTube: