Polar bear seasons: breeding and denning at Hogle Zoo
Utah’s Hogle Zoo is dedicated to protecting vulnerable species under our care and in their natural habitats. One key aspect of this commitment is supporting the natural behaviors of animals in our care, like polar bears.
Facilitating polar bears’ natural reproductive processes is one of the many ways we play an active role in preserving this iconic and vulnerable species.
This journey begins in the winter and spring with the breeding season and transitions into the fall with the denning season. Our animal care team carefully supports each phase. They work tirelessly to create environments and conditions that reflect the bears’ natural cycles while prioritizing their wellbeing.
From fostering bonds during breeding season to preparing for the possibility of cubs during denning, every step highlights the critical connection between conservation efforts and the potential to contribute to the survival of this vulnerable species.
Polar bear breeding season
Polar bears are primarily solitary animals, both in their natural habitat and under human care, and typically only come together in the spring for breeding season. At Hogle Zoo, Nikita (male) and Neva (female) share habitat space each spring for breeding before parting ways in the fall.
During the spring months of the breeding season, guests may expect to see normal behaviors from the bears that our animal care team keeps a close eye on, like:
- Chasing or following each other
- Resting near each other
- Making different sounds, like chuffing
- Sharing toys
- Open-mouth greetings
- Minor wounds
Breeding season can last from a week to a few months—depending entirely on the bears’ behaviors and preferences. Each year, their confidence and comfortability with one another grows.
See breeding season updates:
When facilitating breeding season for the bears, our teams take everything one step at a time and work hard to give them space and time to participate in breeding if they choose. By providing the right environment and closely observing their needs, we help Nikita and Neva thrive in ways that work best for them.
Resident female polar bear, Neva
Resident male polar bear, Nikita
Bulking season
One step in this delicate process is adjusting Neva’s diet for substantial weight gain before denning season begins. Denning is an energetically expensive process for female polar bears. During this time, they don’t hunt or seek food; instead, they rely on fat reserves. Female polar bears gain up to a third of their body weight before denning.
To help Neva reach an ideal denning weight, our team begins increasing her diet in the spring. Over the years, Neva has steadily gained weight, indicating that she’s becoming more accustomed to preparing for denning season. Polar bears rely on sea ice to hunt seals and build essential fat reserves in their natural habitat. However, Arctic ice is now melting earlier in the spring and freezing later in the fall, threatening the polar bear ecosystem and their ability to reproduce. The shrinking hunting season leaves polar bears less time to hunt and fewer opportunities to build the needed fat reserves. Without sufficient sea ice, females may not gain enough weight to support pregnancy.
Delayed implantation
Polar bear breeding and pregnancy are separate events.
Female polar bears experience a unique process called delayed implantation, meaning the bears mate in spring, but if an egg is fertilized, it doesn’t implant until fall—and only if the mother has built up enough fat to safely support herself and her future cubs through denning. There’s no way to know if a female is pregnant or may be experiencing a “pseudopregnancy.” Blood and urine pregnancy tests aren’t effective for polar bears – and with their extra thick layers of fat, ultrasounds also don’t work. Female polar bears may den even if no cubs are on the way.
Polar bear denning season
After several months together during breeding season, the denning season begins in the fall. Female polar bears den to provide a safe, protected environment for potentially giving birth. The keyword here is “potential” – polar bear reproduction is unique and uncertain, and many things must go right.
Supporting Neva and Nikita
When Neva enters denning season in the fall, she is separated from Nikita to support their natural reproductive cycles. While there’s no way to confirm if she’s pregnant at this stage, our teams dedicate months to preparation—ensuring Neva is physically ready. Her denning environment is carefully tailored to her needs.
Neva’s Den
Neva’s den is a quiet, dark, cold space with reinforced HVAC, soft substrate, and soundproofing for minimal disruption. When our team observes Neva calmly nesting and resting through cameras, it shows us she’s comfortable and confident in her space.
See the 2024 denning season update →
Where’s Nikita?
When Neva is in her den, Nikita continues training and interacting with enrichment in his habitat. Our teams carefully think through changes in Rocky Shores designed to support Neva’s denning process – during the denning season, guests may see:
- Less cleaning and maintenance in their habitat to minimize disturbances
- Increased window marks
- Adjustments to BooLights and ZooLights decorations
Guests can visit Nikita in Rocky Shores.
What comes next?
Facilitating polar bears’ reproductive cycles reflects our commitment to the wellbeing of the polar bears in our care. Whether or not cubs are in Neva’s future, each season offers opportunities for us to learn, grow, and refine our approach. We gain new insights into polar bear reproduction every year, allowing us to better support these incredible animals and their natural behaviors.
Neva’s progress each year is a testament to the strong bond and trust she has built with her care team. Polar bear cubs under human care are born between early November and late December. If Neva has cubs, she and her little ones will remain in the den until late spring. If she doesn’t, the cycle will begin again with breeding in the spring, guided by the bears’ needs and choices.
At the heart of everything we do is Neva and Nikita’s wellbeing. We continue taking this process one step at a time, remaining cautiously optimistic, and are prepared to help the polar bears thrive in whatever situation they show us is best for them.
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