Polar Bears: What Happened?

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Chinook pauses between doing her morning laps.

On February14, 2011, and for 10 days after, Chinook and Kalluk were inseparable. They slept together, ate together, swam together, and yes, bred. We can confirm that at this point we will be getting ready for the possibility of polar bear cubs this fall. However, this year breeding came early, and it’s possible we may see Chinook cycle again. It is interesting, as several other zoos with breeding polar bears have experienced this early breeding as well.

The gestation period for polar bears is 195 to 265 days, so before you get out the calendars and calculators, that gives us a due time of August 28 to November 16! To try to get as much information as possible along the way, we are collecting fecal samples and urine samples for hormone assay, and we will again do ultrasound exams with Chinook as we approach implantation and birth time. As you know, she does seem to greatly enjoy her belly-rubbing ultrasound sessions!

Kalluk is still showing a heightened level of testosterone with his behavior and inconsistent appetite. For males in the wild, this lack of eating is proving to be of concern as we lose more ice. In the wild, male polar bears begin searching for receptive females early in the spring. Once they breed with a female, she goes off to hunt and store as much fat as possible while he goes off in search of another receptive female. As the ice disappears earlier in summer, the males are losing precious time to hunt.

Kalluk doesn’t have this worry, as finding food is never an issue. Over the past weeks it has been difficult to get him to acknowledge food, but yesterday he ate 20 pounds (9 kilograms) of meat in one sitting. Kalluk is also beginning to actually sleep; during breeding season, he is so intent on where Chinook is that he rarely does anything more than a quick nap. Both eating and sleeping are good signs that we may be heading back to normal!

Chinook also has some resting to do. Kalluk is twice her size and very attentive to her every move. She is now spending a great deal of time snoozing in our mulch piles or taking long, luxurious swims in the pool. Two days ago Chinook and Kalluk had a great romping play-and- dive session, another sign that “normal” may be right around the corner.

Tatqiq seems to have a great understanding of what breeding season means to her. She is patiently waiting until her friends lose their romantic interests and regain their playful spirits and once again join her in a good romp around the exhibit. Until then, she is greatly enjoying having all the carrots to herself and is busy hunting gophers in Polar Bear Park.

JoAnne Simerson is a senior keeper at the San Diego Zoo. Read her previous post, Polar Bear Dance, where she has responded to questions sent there.