Two Polar Bear cubs were born November 6 at the Columbus Zoo and Aquarium. Animal Care staff observed new mom, Aurora, caring for the newborns. However, despite her efforts, only one cub survived.
Initially, Aurora was caring for her surviving cub, and the Columbus Zoo animal team, in conjunction with recommendations from other Polar Bear breeding facilities, made the decision not to intervene. Polar Bear cubs are difficult to hand rear and disrupting Aurora’s maternal care was not advised.
Unfortunately, last week, the surviving cub was pulled from the den by the Zoo’s Animal Care staff after Aurora stopped caring for it. Aurora began taking breaks from caring for her cub late on the morning of November 19. When these breaks continued throughout the day and became longer, the Zoo’s Animal Care staff made the decision to remove the cub from the den and began to hand-rear the newborn.
At this time, the cub, a female, is healthy and feeding regularly. She weighed in at 1.5 pounds and gained 10 grams soon after Zoo Staff took over. At 2-weeks-old, she is continuing to gain weight, and grows about a half inch every two days. Her nose is turning black and fur is growing on her ears, as well as on the bottom of her paws. Staff will continue to monitor and care for her around-the-clock. The team assesses her daily and makes changes to her routine as need be. They are cautiously optimistic and are pleased with how well she is doing.
Polar Bear reproduction is a very complicated process, which leads to the species having one of the lowest reproductive rates of any mammal. Female Polar Bears generally have their first set of cubs between the ages of four and eight years. Due to delayed implantation, the gestation period can range from about 195 to 265 days. Delayed implantation is a point of time during a Polar Bear’s gestation when a fertilized egg will free-float in the uterus for roughly four months to ensure the cub is born the best time of year for survival.
Pregnant Polar Bears den in the fall and give birth, generally to two cubs, in the winter. The cubs typically weigh about one pound at birth. After birth, the survival rate for a Polar Bear cub during the first few weeks of life is very low due to a number of factors. Some of these factors can be eliminated in a zoo setting though this is still a very delicate time for a newborn.
Polar Bears, much like Giant Pandas, are highly specialized animals that give birth to very small babies, which makes them fragile during their first year of life. Survival rates in human care are around 50%, which is similar to that of wild bears.