First panda cubs born in Canada at Toronto Zoo

Two one-day-old giant pandas are seen at the Toronto Zoo Tuesday, Oct. 13, 2015. (The Toronto Zoo)

The Toronto Zoo is celebrating a Canadian first with the birth of two tiny, pink panda cubs.

Giant panda "Er Shun" gave birth to the bear cubs at the zoo on Tuesday at 3:31 a.m. and 3:44 a.m. The zoo also released video of one of the births on YouTube Tuesday morning.

"Er Shun is demonstrating excellent maternal instincts and began cleaning and cradling the first cub soon after its birth," the zoo said in a statement on Tuesday. The cub weighed 187.7 grams at birth.

The mother has also bonded with her second cub, who weighs only 115 grams.

"While this is wonderful news, the tiny cubs are very vulnerable at this size, so the next several hours and days will be critical to their survival," the statement said.

The cubs will remain in a maternity area of the giant panda house for several months, and will not be visible to the public until mid-March.

Er Shun will only see one cub at a time while the babies are nursing, the zoo said in a post on Facebook.

Twin births are common, but mothers instinctively only nurse one of their cubs, often abandoning whichever is considered weaker. When it becomes clear that one cub is healthier, they will focus their attention on that cub.

In an attempt to make sure Er Shun takes care of both bears, Toronto Zoo staff will swap the babies in intervals. While one is nursing, the other will be in an incubator and monitored by staff. The cubs will be switched approximately every two hours.

Officials have not yet said whether the cubs are male or female, nor have they identified the bears' father.

The guinea pig-sized bears are the first giant pandas to be born in Canada, and were conceived through artificial insemination.

The cubs' 8-year-old mother was inseminated in April 2014, but the attempt was unsuccessful. She was inseminated again in May as part of a worldwide giant panda captive breeding program.

Zoo officials said the procedure was necessary because the lumbering female wasn't "jiving" with her male partner, 7-year-old Da Mao. Reproductive scientists used sperm collected from Da Mao, as well as frozen sperm from two giant pandas living in China.

The cubs' father will be determined by DNA testing in "several weeks," once the proper permits have been obtained for sending blood to a lab that specializes in panda DNA, the zoo wrote on Facebook.

The cubs will remain at the Toronto Zoo when their mother leaves for Calgary in 2018. Er Shun and male panda Da Mao are on loan to Canada from China for 10 years, five of which are being spent in Toronto, and five which will be spent in Alberta.