TORONTO — The panda watch is on, and the mood is tense at the Toronto Zoo as staff wait — and hope — for successful births of two panda cubs some time in mid-October.
Er Shun, one of two giant pandas on loan from China, is pregnant with two fetuses, said Gabriela Mastromonaco, the zoo's curator of reproductive programs and research.
"There are so few pandas that whenever one is born, the implication is so huge," Mastromonaco said in an interview.
There are only about 1,800 pandas in the wild, according to Chris Dutton, the zoo's head of veterinary services. A few hundred live in captivity.
Dutton expects the pair to be born, if all goes well, by mid-October.
Mastromonaco can't say for sure whether the pair will be twins because sperm from three different donors was used during the one-day window back on May 14.
"We can't say that they are truly twins until we find out who belongs to whom," Mastromonaco said, adding that genetic testing can only be done once the cubs are born.
The zoo's other panda, a male named Da Mao, was given the opportunity for a "natural insemination," Mastromonaco said.
But Da Mao and Er Shun didn't look like they were going to play nice, she said, because they were "chuffing" at each other and showing signs of aggression. So zoo keepers didn't remove the mesh that separated them and pulled Da Mao out.
Then they anesthetized him and performed "electro-ejaculation" to get some fresh sperm. Dutton said that involved the insertion of a rectal probe to "stimulate the right nerves" and achieve ejaculation.
Staff mixed that sample with frozen sperm from two pandas from China, sedated Er Shun and inseminated her without surgery, Dutton said, in the same manner humans are artificially inseminated.
Then it was a waiting game. Dutton said they began performing ultrasound examinations at regular intervals. The ultrasound examination itself is a touch precarious as staff had to teach the panda to lie down near the cage and relax as they probed the outside of her abdomen. Apples help Er Shun chill out.
As a keeper fed apple slices to Er Shun on Friday, Dutton and Cathy Gartley, a veterinarian from the Ontario Veterinary College at the University of Guelph, saw an embryo pop up on the black-and-white screen of the ultrasound.
Then they heard the heartbeat.
"It was an incredible moment," Dutton said, "but we couldn't scream with joy because we just can't do that around a panda."
On Tuesday, the team went back to have another look at the other side of Er Shun's uterus. Another embryo and another heartbeat showed up.
"I had a few choice words in my excitement — it's not something I will repeat, but we were really, really happy," Dutton said.
They remain "cautiously optimistic" about the upcoming births.
Then the pair, if they survive, will live at the zoo for about two years and will likely return to China once they are weaned from Er Shun, Mastromonaco said.
Er Shun and Da Mao arrived from China in 2013 and are slated to move to the Calgary Zoo in 2018.
