The survival of polar bear cubs depends heavily on the extensive care provided by their mothers. The harsh Arctic environment makes this maternal bond particularly important for cubs to develop the necessary skills for independent life. This long period of parental investment ensures the next generation of bears is prepared for the challenges of their icy habitat.
Life in the Den
Polar bear cubs typically begin their lives in snow dens, usually born between November and January. At birth, they are tiny, blind, toothless, and weigh little more than 0.5 kilograms (1 pound). The mother remains in the den, fasting and nursing her cubs with extremely rich milk, which contains about 31-33% fat. The cubs grow rapidly on this high-fat diet, protected from the extreme cold and potential predators inside the den.
Mother and cubs generally emerge from the maternity den in March or April when the cubs are approximately three to four months old and weigh between 10 to 15 kilograms (22-33 pounds). After emerging, the family often remains near the den for about 12 days to a few weeks, allowing the cubs to acclimate to the frigid Arctic air and strengthen their muscles. This initial period outside the den is a transition before they venture further onto the sea ice.
The Period of Maternal Care
Polar bear cubs stay with their mothers for an extended period, typically ranging from two to 2.5 years. This duration allows the mother to guide her offspring across the sea ice, providing both sustenance and protection. Cubs continue to nurse for at least 20 months, with some nursing for as long as 30 months. During this time, the mother is responsible for teaching them how to survive in their demanding environment.
Several factors can influence the length of this maternal care period. These include the mother’s health, the availability of food resources like seals, and the presence of other cubs in the litter. A mother bear will generally be ready to breed again when her cubs are around 30 months old, which often coincides with their separation.
Essential Skills for Survival
During their time with the mother, cubs acquire a range of skills necessary for survival in the Arctic. They learn how to hunt seals, their primary food source, by observing and mimicking their mother’s techniques. While cubs may begin practicing hunting as early as three to four months old, they are typically not successful hunters until they are over a year old. Even at two years of age, cubs might only spend about 7% of their time hunting.
Mothers also teach their young how to navigate the complex and ever-changing sea ice, identify safe areas, and avoid dangers such as adult male polar bears or thin ice. Learning to conserve energy and understanding migration patterns are also part of this education. The prolonged period of dependency allows for the mastery of these complex behaviors, which are essential for their future independence.
Transition to Independence
The process of separation occurs when the cubs are ready for self-sufficiency. This typically happens when the cubs are between two and three years old, at which point they are referred to as subadults. The mother will eventually encourage them to disperse, sometimes by simply leaving them or by chasing them away. The cubs then must apply the lessons learned during their long period of maternal care.
These newly independent subadults face significant challenges, including finding sufficient food. The initial years of independence can be particularly difficult, and they face a high mortality rate. However, the thorough preparation provided by their mother equips them with the foundational knowledge and skills needed to navigate the Arctic wilderness and eventually thrive as adults.