10/13/2015 09:06 EDT | Updated 12/23/2015 10:59 EST

Baby Twin Pandas Born At Toronto Zoo

TORONTO — The highly anticipated birth of two giant panda cubs at the Toronto Zoo was being hailed Tuesday as a Canadian first.

The zoo said the cubs were born between 3:30 and 3:45 a.m., the first weighing just under 188 grams and the second 115 grams.

Their mother, Er Shun — who is on loan from China along with a male panda named Da Mao — is showing "excellent maternal instincts" and has been given time to bond with each cub as they take turns in an incubator, the zoo said.

All three appear to be doing well, the zoo said, and will be monitored around the clock in the panda maternity ward, which is closed to the public.

"The tiny cubs are very vulnerable at this size, so the next several hours and days will be critical to their survival," the zoo said in a statement.

giant baby panda cubs

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.

According to a statement from the Toronto Zoo, if all goes well, the new pandas should be on exhibit by mid-March, 2016.

Here's the full Facebook post with more information from the Toronto Zoo:

We are very excited to announce a Canadian first today with the birth of two giant panda cubs! Er Shun gave birth to her...

Posted by The Toronto Zoo on Tuesday, October 13, 2015

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