On January 4, we came in to find it had begun and Kalluk and Chinook were inseparable. After a week of togetherness, it was all over for Chinook, but that was when Kalluk’s breeding drive took off. During the months that followed, we spent lots of time preparing foods that our boy would find appetizing to help keep any weight on him while nature takes over and he loses his appetite and seems to endlessly search for other mates. We also try different management techniques to see if any help to ease the road for Kalluk.
In the wild, male polar bears also go off their food in an effort to find receptive females. They, too, can lose an enormous amount of weight during this time, but adult males can make it up after breeding as they hunt yearlong on the ice and don’t have the need to fatten up to survive months in the den producing milk for cubs! However, with the summer ice beginning to disappear earlier, and knowing that males can be in breeding mode until June, it is worrisome to know what effects this could have on our wild male populations.
Polar bear breeding season can last into June, so although it is still possible that Chinook and Kalluk could breed again, Chinook’s behavior indicates that it is not likely. Kalluk is also showing fewer behaviors to indicate this as well. What does all this mean? We don’t have the exact answers, but it is likely that when the breeding occurred in January, Chinook ovulated, and if the egg was fertilized, she would not have the biological need to breed again. If this were in the wild, she would have begun hunting and storing as much body fat as possible to rear her cubs. It is interesting that so far this year she has been gaining weight more so than any year previously at this time.
The actual weight of polar bear cubs would not have a significant impact on their mother’s weight. Cubs are, after all, less than 2 pounds (1 kilogram) at birth. But we are optimistic that Chinook’s weight gain is an indicator that her body is holding on to every calorie she would need in the future for cub rearing.
Kalluk and Tatqiq have renewed their bond and can now be seen wrestling and playing together. Chinook is spending her days relaxing, eating carrots, and taking those beautiful, long soaks in the pool. She has quite a “full” figure these days; actually, she is gorgeous! So the warm San Diego summer will have her lounging and soaking most of the time. She will, of course, be given the option of staying in the air-conditioned bedrooms so you may not see her as much as in previous summers.
We know the question is already there: is she or isn’t she? We don’t know. We will continue to work on research to give us better answers, continue to monitor Chinook’s behavior to provide for our girl exactly what she needs, and keep all fingers and toes crossed. We’re all getting pretty good at that!
JoAnne Simerson is a senior keeper at the San Diego Zoo. Read her previous post, Polar Bears: Hormones.