The Saint-Félicien zoo has a new resident — a brand new polar bear cub who was born in captivity this week.

Because polar bear pregnancies are hard to predict and very rare in captivity, animal-care workers at the zoo came into work Tuesday morning to a big surprise: the cries of a newborn coming from the mama bear's lair.

"We are really, really happy about this birth," said Christine Gagnon, a biologist and director of conservation and education at the Saint-Félicien zoo, which is 300 kilometres north of Quebec City.

The new baby weighs about 600 grams, while the mother bear, Aisaqvak, weighs a whopping 330 kilograms.

Animal care workers at the zoo didn't know for sure that Aisaqvak was pregnant until they heard the baby's cries on Tuesday. (St Felicien Zoo)

Gagnon explained that because of the baby's small size, it's impossible to tell if a female polar bear is pregnant by sight alone, and urine testing is unreliable.

As of 2015, the total population of polar bears in zoos and aquariums worldwide was 298. Only around half the cubs born that year survived longer than 12 months.

Aisaqvak gave birth to two cubs in 2009, both of whom are hale and hearty at nine years old. The male, Ganuk, lives at the Toronto Zoo. The female, Taïga, is at the Aquarium du Québec.

UN CADEAU DE NOËL À L'AVANCE! 🤩<br><br>Le 27 novembre dernier, la femelle ours blanc Aisaqvak a donné naissance à un ourson! La maman et le petit se portent bien. Voyez quelques images des trois premiers jours dans la tanière! L’ourson sera visible au public d’ici environ 3 mois. 😍 <a href="https://t.co/5eGYR6fzxt">pic.twitter.com/5eGYR6fzxt</a> —@zoostfelicien

Since then animal-care workers have repeatedly tried to get Aisaqvak pregnant again, with no success until now.

"We had to wait all these years for her to have another little one," said Gagnon. "It's really special."

The new cub doesn't have a name yet, and animal-care workers don't know its sex because they haven't yet taken a close-up look.

Mama bear Aisaqvak with the two cubs from her 2009 litter, Ganuk and Taïga. (Mathieu Belanger/St Felicien Zoo)

But they have been monitoring the small bear's progress from a camera positioned inside the lair.

Gagnon said Aisaqvak has been dutifully caring for her cub, which she described as "the best-case scenario."

This cub's birth is particularly promising, said Gagnon, because Aisaqvak was a wild polar bear found in northern Quebec.

The Saint-Félicien zoo renovated its bear habitat earlier this year. (St Felicien Zoo)

The father, a 13-year-old male named Yellé, also had a parent who was born in the wild, adding to the gene diversity within the small pool of bears held in captivity worldwide.

Visitors will be able to see Aisaqvak and her cub starting in spring 2019, when the baby is about three months old.

A brand new habitat was created for the bears this year, which zoo administrators are hoping will help coax the little one out of the lair and ease its adaptation.