Life Cycle | Polar Bears International

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Photo: Daniel J. Cox

Life Cycle

For female polar bears, the cycle of life includes mating, denning, and giving birth to cubs.

Photo: Kieran Mulvaney

Mating (Spring)

Between April and late June, male polar bears search for female mates on the sea ice by following scented trails left by footpads.

Mating takes place on the sea ice. But the fertile eggs don’t implant until the fall, and only if the female has enough fat to sustain herself and her cubs during the long denning period. This process is called delayed implantation.

After mating, adult males remain with the female for a few days before taking off on their own.

Photo: Daniel J. Cox

Denning Fall & Winter

After feeding through the summer and fall, gaining as much weight as possible, pregnant female polar bears prepare to enter maternity dens to give birth to their cubs. To build a den, the female digs a small snow cave in a snowdrift —just large enough for her to turn around. She then waits for the snow to close the entrance tunnel and completely hide the den under the snow.

Birthing (Winter)

Wild polar bear cubs are most often born in December. The mother gives birth to 1-3 cubs, with twins most common. The family remains in the den until spring. While in the den, the mother bear doesn’t eat or drink. She is devoted to nursing and caring for her cubs.

Photo: Daniel J. Cox

Polar Bear Cubs

Totally dependent on their mothers, newborn cubs are blind, toothless, and covered with soft white fur. They weigh little more than 1/2 kg (1 lb) and are just 30-35 cm long (12 to 14 in). The cubs grow rapidly on their mother's rich milk (31% fat) and continue nursing for at least 20 months.

Photo: Daniel J. Cox

Emerging from then Den

Polar bear families generally emerge from their dens in March or April when the cubs are strong enough to survive in outside Arctic conditions and make the trek to sea ice.

Now, mother bears can start teaching their young how to hunt seals on the ice and survive in the Arctic.

Learn More About the First Few Months of a Polar Bear's Life

In the Den

After birth, mom and her cub(s) will spend several months snuggled up in their den until they are big and strong enough for a life in the Arctic.

Emerging From the Den

After they emerge for the first time, Mom and her cubs will remain at their den for a few days or weeks, giving the cubs a chance to play, explore, and strengthen their legs. Cubs also use this time to become accustomed to the frigid Arctic air!

Growing Up On the Ice

A mother polar bear will begin teaching her young cubs how to hunt and how to survive in the Arctic.

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Growing Up

Polar bear cubs generally stay with their mothers for 2.5-3 years, learning how to hunt, feed, swim, and survive.

Between the time they leave their mother and are mature enough to mate, polar bears are called subadults.

Reaching Adulthood

Polar bears are considered adults when they are old enough to mate. For females, this is ages 4-6, for males 6-10.

By the time they reach adulthood, adult males normally weigh 350-600 kg (775-1,300 lb). Adult females usually weigh 150-295 kg (330-650 lb), though some can be larger.

Life Span

In the wild, polar bears live an average of 15 to 18 years, although biologists have tagged a few bears in their early 30s.

Name and Evolution

Discover the many names for polar bears and how they evolved from brown bears.

Adaptations & Characteristics

Learn how polar bears are built for the Arctic and a life on the sea ice.

Name and Evolution

Discover the many names for polar bears and how they evolved from brown bears.

Adaptations & Characteristics

Learn how polar bears are built for the Arctic and a life on the sea ice.

Polar bear on ice looking down at the ocean

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