We are all on pins and needles to see if the San Diego Zoo’s polar bears, Kalluk and Chinook, will breed this year. They have always been early birds by breeding in March and even as early as February! But normal breeding time for polar bears is April through May and sometimes as late as June, something we won’t even contemplate! From the looks of how flirtatious Chinook has been and how attentive Kalluk seems, our patience should be rewarded.
We are still participating in reproductive studies looking at hormones excreted in the bears’ urine and feces, but for the most part we still rely on behavior observations. One of the very interesting behaviors we see is with Chinook. Typically, a week before actual breeding and continuing right up to actual, we see her have seizure-like spasms followed by weakness in her back legs. The spasms last only seconds and the weakness only a few minutes. If you don’t know what these are, they can be very scary to see!
But there is no need to worry: Chinook is not alone with these. Most of the other breeding female polar bears show the same behavior. I have asked polar bear biologists who have spent many years observing bears in the Arctic and have sent them video of the process, and they are mystified as to its purpose. Perhaps it plays some role in preparing a female’s legs to hold the male during breeding, since males are usually twice the size, and she may bear his weight for long moments. In the last week we have seen Chinook have these spasms, and over the last few days they have increased both in frequency and intensity. This should be a sign that we are almost there!
We all know what follows: waiting to see if Chinook becomes pregnant and gives birth. I have been getting lots of experience working with polar bear cubs over the last few years since Kalluk and Tatqiq joined us as cubs in 2001. I have just returned from a second visit with Siku, the polar bear cub born at the Scandinavian Wildlife Park in Denmark. My first visit was to share what we learned in preparing our polar bear youngsters for life in San Diego. Siku still was not yet walking then and was not quite 13 weeks old. On my recent trip, Siku was now 21 weeks and was walking, running, swimming, and being overall an adorable monster!
Since Siku’s mom did not produce milk, the decision was made to hand raise him, which meant having close contact with him (not a problem when his fastest speed was a quick crawl!). He is now rambunctious and, as polar bears need to do, he is jumping, grabbing, and mouthing everything and everyone in sight. Mom polar bears are well equipped to handle this; human caregivers, not so much!
This trip was to help the team in Denmark move ahead with management that increases Siku’s independence and encourages his natural instincts as a polar bear. He did extremely well with every challenge of independence. You can imagine how difficult it is, though, for the team who has been caring for him all these months to see that maybe he didn’t need them as much anymore, or at least not in the same ways. I must say how proud I was to assure them and show them the close ties we have with our three polar bears and how much that strengthens when you’re not worried about when the next play jump comes from a now 60-pound and often wet white ball of teeth and claws! All meant in fun, but still dangerous for fragile humans!
Siku has lots of toys to encourage his natural learning behavior and is getting plenty of opportunities to learn with his training sessions. At 21 weeks, he has already learned several important behaviors from his keepers such as “sit,” “stand,” “down,” “shift,” “come,” and how to sit on a scale.
In choosing his name, thought was given to the chance to represent wild polar bears and the people who share the Arctic. Siku is from the Inuit language for sea ice. Siku will remind everyone that we are losing our arctic ice due to warming trends in our climate. Science has proven this warming is caused by the increase of carbon emissions in our atmosphere. Siku and our three polar bears, Chinook, Kalluk, and Tatqiq, are ambassadors who remind all of us of their wild cousins and that we must make changes to help save their arctic home.
As you enjoy watching and hearing about these great ice bears, please keep in mind everything you can do to help. Then do it!
JoAnne Simerson is a senior keeper at the San Diego Zoo. Read her previous post, Polar Bears: Back to 3.
UPDATE: Two days after this was written, Kalluk and Chinook began breeding. November 2 is the first possible day of birth if Chinook is pregnant! The waiting begins. . .