Giant pandas once roamed the lowlands of southern and eastern China. But as humans encroached on their territory and destroyed their land, they were forced out of the lowlands and are now only found in six mountain ranges in central China. They are considered an endangered species, with giant panda populations estimated at 300 in zoos and reserves and just 1,600 to 3,000 in the wild.

To complicate things more, Mastromonaco says that pandas have a very slow rate of reproduction compared to other animals.

Giant pandas have a brief window of opportunity to breed, with female pandas having only one reproductive cycle each year. Females only mate for 24 to 72 hours.

When this window opens up for Er Shun next spring, Mastromonaco says the zoo will first try to breed her with Da Mao, giving natural breeding a chance. But if that doesn’t work after 24 hours, they’ll have to use other methods to avoid losing that breeding season.

Zoos have tried different things to encourage breeding, including showing male pandas videos of successful breeding so they know how to hold each other. Some have even tried Viagra.

Although many zoos attempt natural breeding, there hasn’t been much success. Mastromonaco notes that if a pair of pandas isn’t compatible, it becomes difficult to breed them.

“That is one of the reasons why assisted reproduction became so important in the species,” she says. “We still don’t know what we have, what type of pair we have here,” she says, adding that they may not be compatible.

Zoos often need to use artificial insemination to produce panda offspring. Research suggests that artificial insemination is as effective as natural breeding, with pregnancy rates near 60 per cent. Artificial insemination was successful in producing the twin boy pandas born at the Atlanta Zoo on July 15.

Although Mastromonaco says there are breeding benefits to having pandas in zoos, Patrick Tohill of the World Society for the Protection of Animals in Canada says “history doesn’t seem to indicate that.”

“I think we’re a long way away from using captive breeding and zoos to boost the numbers in the wild,” he says, adding that he believes the expenses incurred transporting pandas to zoos is better spent on preserving the pandas’ habitat and food sources in China.

Tohill says that in the wild, males compete for the female’s attention, and mating may take place several times over the brief window available each year. On the other hand, he says that in zoos, the male panda often shows no interest in mating with the female.

There is usually a new panda cub every couple of years in the wild, Tohill says, whereas in captivity, they haven’t been quite that successful.

Mastromonaco understands why some critics think pandas should be left in the wild and not kept in captivity, and she isn’t against animals being in the wild. “The only problem is that as humans, we have impacted them,” she says, pointing out that if pandas are left in the wild on their own, they will disappear.

“Maybe what we’re doing is not perfect, but it’s something.”