A panda on loan from China gave birth to two cubs Tuesday morning, but the Toronto Zoo says the public won't be able to see them for a few months as they face a critical time for their survival.
The cubs — the first weighs just under 188 grams and the second 115 grams — were born between 3:30 and 3:45 a.m., and "are doing very well," said zoo spokeswoman Jennifer Tracey.
The zoo has no immediate plans to show or even name the cubs.
"They're so small and so vulnerable at this age we don't want to get ahead of ourselves," said Tracey.
Their mother, Er Shun — who is on loan from China along with a male panda named Da Mao — is showing "excellent maternal instincts," she said.
"Er Shun has been an amazing mom today. For a first-time mom she is doing really, really well."
The first 30 days of life are critical, Tracey said.
The zoo has been swapping the cubs between their mother's care and an incubator set up in a quarantined room next to the panda's maternity ward, which is closed to the public.
Chris Dutton, the zoo's head of veterinary services, previously said allowing Er Shun to care for two cubs at a time would likely lead to the death of one due to neglect.
There are two keepers from China in town to help with the cubs' neonatal care.
Tracey said the zoo has the capability to broadcast live from the maternity ward, but hasn't made any plans to do so yet. In the meantime, she said, the public will receive updates through videos and photographs via social media.
Giant pandas are born blind and the cubs are pink with short, thin white fur. The cubs are about 1/900th of the size of their mother, making them among the smallest newborn mammals compared to their mother.
Sperm from three different donors — Da Mao and two pandas in China — was used during the one-day fertility window back on May 14, and it's unclear whether the cubs are twins.
"At this time zoo staff do not know the sex of the cubs and have not confirmed which panda is the father. It may be several months before we are able to determine the sex and paternity of the cubs," the zoo said.
Zoo staff began conducting regular ultrasounds on Er Shun and announced the pregnancy in late September.
The zoo said it's the first time giant pandas have been born in Canada.
Staff have said the cubs, 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. Er Shun and Da Mao arrived from China in 2013 and are slated to move to the Calgary Zoo in 2018.
It will be a difficult road ahead. Two cubs were born in Washington's National Zoo in August and one cub died four days later. The zoo said the cubs' mother didn't take to the cub-swapping.
The National Zoo said the mortality rate for panda cubs in human care in their first year is 26 per cent for males and 20 per cent for females.