Breeding season for polar bears is typically January through June. For Kalluk and Chinook in particular, it can happen anytime in that window. This year, the breeding window began on April 23, 2014, and usually lasts anywhere from 4 to 14 days. In 2013, it occurred in January and only lasted four days. This year, we are seven days into the process and breeding is still happening. However, the frequency has diminished quite a bit from the first few days.
Science still knows very little about polar bear reproduction. What we do know is that polar bears are both induced “ovulators” and delayed “implanters.”
Induced ovulation means that the females don’t have a normal estrus cycle like many mammals do. Male bears follow around females for days or weeks at a time, “wining and dining” them until they are receptive to breeding. Once ovulation is induced, then breeding will commence.
Delayed implantation is tricky because it makes gestation periods and birth dates difficult to predict. Unlike most mammals, after polar bears successfully copulate, they are not immediately pregnant. The fertilized egg remains in a suspended state until conditions are right, at which point the egg implants in the uterus and gestation can begin.
Until late May/early June, Tatqiq is, unfortunately, the odd bear out. Chinook’s hormones are raging, and she is less tolerant of Tatqiq during this time period. Kalluk generally does a good job of breaking up squabbles and moving his sister to a safer spot away from Chinook. If you have been watching the Polar Cam in recent weeks, you have probably noticed Tatqiq seeking refuge in the back corner near the waterfall. This is her safety zone and the spot where she feels she can best defend herself. It is our job as keepers to recognize these changes in behavior and adapt our management strategy. Because of the increased tension between the two females, you will usually only see Kalluk and Chinook on exhibit after 12:30 p.m. When the keepers pull the bears off exhibit for their final meal of the day, we give Tatqiq the polar bear penthouse where she has her own private pool, grass, trees, and air-conditioned bedrooms.
Once breeding season is over, you will again see Kalluk and Tatqiq playing together and there will be less aggression between the two females. Be sure to watch the action daily on Polar Cam!
The Polar Bear Team