Former Oregon Zoo Polar Bear Nora May Be Pregnant After Gaining 237 Pounds

Nora, a polar bear who formerly lived at the Oregon Zoo, has gained 237 pounds in recent months as keepers at Wisconsin’s Henry Vilas Zoo monitor her for a possible pregnancy.

Keepers Monitor Nora for a Possible Pregnancy

The zoo announced Thursday that Nora’s weight increased between March and September, a potential sign of pregnancy and preparation for denning.

Polar bears cannot be reliably pregnancy-tested, and ultrasounds are ineffective because the bears’ thick layer of insulating fat prevents clear imaging, according to the zoo.

Nora’s keepers are keeping a close eye on her, and her denning suite’s camera system has been upgraded. The first few weeks of a cub’s life are especially risky, the zoo said. First-time mothers such as Nora also face higher cub mortality rates than bears that have given birth previously.

December or January are the likely dates she will give birth.

Nora’s History at the Oregon Zoo

Born Nov. 6, 2015, at the Columbus Zoo and Aquarium in Ohio, Nora was hand-reared after her mother began leaving her unattended for extended periods.

She arrived at the Oregon Zoo in September 2016 before moving to Utah’s Hogle Zoo in 2017, where she lived with another female polar bear, Hope.

Nora returned to Portland in 2021, joining the Oregon Zoo’s new Polar Passage habitat. She later moved to Henry Vilas Zoo as part of a coordinated effort by accredited zoos to maintain a genetically diverse polar bear population and give her an opportunity to raise cubs.