polar bear pregnancy


Polar Bear Ultrasound

Will these two become parents this year?

Pieces of the Puzzle

Yes, we have begun the ultrasound exams with Chinook! Yes, she is cooperative, and we are very hopeful that this will be the year that once again we will have polar bear cubs at the San Diego Zoo. But how difficult is it to ultrasound a polar bear who is wide awake? The pieces of the puzzle are coming together.

The first puzzle piece, training, was relatively easy. Due to the great trusting relationship between Chinook and her keepers, and the history of learning together, teaching Chinook to roll over and hold went quickly. The next part was to get her to accept the ultrasound gel and actual probe on her belly. Chinook does very well with it all. And please keep in mind she is the only polar bear in the world who is trained for the ultrasound procedure.

We tend to take for granted the use of ultrasound to diagnose pregnancy. It is almost commonplace now. It wasn’t that long ago when ultrasound exams on our giant panda Bai Yun were also history in the making! Again one of the challenges is to find a very small fetus in a very big bear and ensure the safety of Chinook, the veterinarian, and, of course, the ultrasound probe! We are lucky to have many talented folks at the Zoo who have helped in designing and building various pieces of the puzzle. We now have a specially molded probe holder and removable bars on our training crate that allow for better movement of the ultrasound probe.

Every ultrasound image is recorded for review by our veterinary staff. We are confident that “when” (positive thinking) polar bear cubs begin to develop, we will be able to see them well and document another historical event: first-ever in utero polar bears!

Until then, we continue to collect urine and fecal samples to chart Chinook’s hormonal changes and monitor her behavior for dramatic and subtle changes that will alert us to her needs for a successful pregnancy and rearing of polar bear cubs. The cameras, microphones, and recorders are all ready, as long as she chooses those areas to den!

Now that we have all the pieces to the puzzle for our Chinook, it is important to remember that there are many pieces of polar bear reproduction that are missing. Much of our research with polar bear sensory ecology (see post Polar Bears: Getting Ready) will help shed light on pieces of the puzzle that would be very difficult, if not impossible, to do in the Arctic. To be able to document a polar bear pregnancy may give us more information on how to better protect polar bear maternity areas at critical times as more environmental impact jeopardizes the survival of our wild polar bears. How wonderful to be part of keeping polar bears in our future and not just a part of our history.

JoAnne Simerson is a senior keeper at the San Diego Zoo. Read her previous post, Polar Bears: Dare to Hope.

Update October 28, 2011: Both ultrasound and fecal hormone analysis look possible, but nothing is confirmed yet. Keep everything crossed!


Polar Bears: The Latest

Kalluk grabs a carrot snack.

It’s hard to believe summer is a distant memory, and fall is quickly passing. Can we already be into the middle of November? Six months ago we were all so sure our Chinook would be caring for cubs. We’ve not yet given up, but the wait and uncertainty is almost un”bear”able. We will just have to wait a bit longer to know if we will be welcoming any cubs to our family.

Here is what we do know: as of the last analysis of hormones, October 12, Chinook had not yet had any embryos implant, but her levels were still close to what we would expect of a potentially pregnant polar bear. So if she is pregnant, we would now not expect to see any cubs until late November or early December. We must still keep in mind that these tests are not a perfected science, and we still have many things to learn.

Chinook’s weight has now stabilized, and she is no longer gaining weight; still, she is very picky about what she will and won’t eat. Again, something seen in polar bears that have given birth. Chinook’s behavior seems to be moving away from what we would expect; instead of slowing down, she is becoming more active. This is not entirely a sign of no pregnancy; some females show heightened activity just before they den up. These are typically females that give birth shortly after denning.

Do we dare hope that this is Chinook’s plan? As it has always been here at the San Diego Zoo, Chinook’s needs will dictate everything we do for her. Is she just learning that every fall, if she slows a bit, we begin catering to her every need and give her more  “me” time and spa days? And of course she gets those special days of peanut butter soup and belly rubs for ultrasound procedures. She is a very smart girl! Unfortunately, we have yet to see any cubs with the ultrasound. Not to be discouraged: our veterinarians remind us they did ultrasound for three years before they saw a cub with our giant pandas!

Kalluk and Tatqiq are having a great time together. They certainly are enjoying rambunctious water play and daily dirt pile rolls! It would appear Chinook is now not the only dirt bear expert. In the event Chinook does not den up, we would look to putting our threesome together as soon as possible. I shudder to think what the pool will look like with three huge dirt balls jumping off the point!

Fall is also the time when Chinook’s cousins in Churchill, Manitoba, Canada, begin to gather at the shore and wait for the ice to form. I am on my way north for my 10th year in this one-of-a-kind polar bear world. Selfishly, I’m hoping that if Chinook is to give birth, she will wait for me to come home in December. I am also concerned with what I might see with the wild polar bears. This past year saw the shortest recorded ice formation for the Hudson Bay population of polar bears. Not only did it freeze up four weeks late, it also melted five weeks early. The bears had barely six months to hunt. The forecast is not looking any better, and warmer-than-normal temperatures are expected throughout Canada’s Hudson Bay. Although a few degrees may not seem like much, the difference between water and ice is the difference between 33 and 32 degrees Fahrenheit (0 and -0.5 degrees Celsius). A small amount can, in the end, make a huge difference.

What other small thing can you do to reduce your carbon footprint and encourage others to do the same? In the end, it could make a huge difference.

JoAnne Simerson is a senior keeper at the San Diego Zoo. Read her previous post, Polar Bear Hopes.

Watch the Zoo’s polar bears daily on Polar Cam.


Polar Bears: A Quiet Fall?

Only Chinook knows for sure...

Changes have begun at the San Diego Zoo’s Polar Bear Plunge. You may have noticed that Chinook has spent the last few weeks with Kalluk and Tatqiq for less periods of time. We have been watching her behavior and started to decrease her time with them as she began to show no interest in interacting with them and even began to push them away.

Female polar bears require great quiet, security, and seclusion when they den. Interestingly, it was Kalluk whom Chinook first began to let know he was not welcome too close. For the next few weeks, Chinook will most likely be out in our large exhibit only in the mornings for a few hours, and then she will spend the rest of her day in the off-exhibit management yard we call Polar Bear Park and the adjoining bedrooms while Kalluk and Tatqiq take residence for the rest of the day in the exhibit.

Chinook’s change in behavior is normal for a female polar bear that is pregnant. Her den is installed, and the bedrooms that will act as outer chambers to her den are cozy and quiet. Yes, we have the cameras installed so when the time is right we will be able to share any greatly hoped-for additions to our polar bear family with anyone viewing Polar Cam. Is Chinook pregnant? When will she give birth? We don’t have the exact answers to these questions, but we sure are hoping for good news this fall!

Here’s what we do know: in March of this year, Kalluk and Chinook engaged in what appeared to be very successful breeding behavior. Polar bear gestation is 195 to 265 days. Counting it out, we would expect to see cubs born between October 9 and December 15. The majority of polar bears cubs in the U.S. have been born in late November, but the earliest was October 11. You can see Chinook’s timeline is well within normal timing!

We have also been participating in a fecal hormone study done by the Cincinnati Zoo’s CREW (Center for Conservation and Research of Endangered Wildlife). The study is working to develop a test to be able to confirm pregnancy in polar bears and also be able to differentiate between actual pregnancy and false pregnancy. If the current numbers and protocols are correct, then Chinook’s hormones indicate that yes indeed she is pregnant! But at this point this is not a perfect measurement, so again we have a level of uncertainty that only seeing cubs will remove.

Luckily, Chinook is the only polar bear in the world currently that is trained for ultrasound procedures! We have regularly been doing these exams every week. We have yet to find anything but all the normal abdominal parts. It is very much like the first years with our giant pandas. . .so much to learn! How do you find a fetus the size of a peanut in a 200-plus-pound panda? Well, you can imagine the challenge when the bear is a 600-plus-pound polar bear! Suffice it to say that even if we don’t confirm pregnancy with ultrasound, it doesn’t mean Chinook is not pregnant. But how exciting it will be if we can confirm and have the first-ever images of a polar bear cub before birth!

Soon we expect Chinook will want only to be in the park and bedroom/den area. Kalluk and Tatqiq will spend their time in the exhibit keeping up their wonderful work as ambassadors. And I suspect we’ll all be crossing our fingers just a little bit harder! Patience . . . patience . . . patience. . .shhhhhh, it will be a quiet fall!

JoAnne Simerson is a senior keeper at the San Diego Zoo. Read her previous post, Polar Bears: Oh, Miss Chinook!

Note: JoAnne has provided some answers to questions posed in her previous post


Polar Bears: What IS Going On?

Tatqiq explores the new yard.

Tatqiq explores the new yard.

Good question! First, the construction is done. The new management yard has only the aesthetic details to be done: topsoil, planting, logs, etc. Most of this will be done over the next few weeks as time permits or if/when Chinook decides she no longer needs to venture anywhere but her den.

Yes, all is complete inside for Chinook to remove herself whenever she wants. Every day our girl lets us know how she is doing. Mostly she is content hanging out with her keeper in the bedroom area while we work. But sometimes she still wants to go out to the yard or the exhibit to enjoy a quick soak and rub and then come back inside. Yes, she is still very cooperative for ultrasounds each week. And we’ve not yet been able to detect a pregnancy. So keep your fingers crossed! Remember: with the delayed implantation and length of gestation, we may not see cubs until next year if we count from the last day of breeding. Oh, a long wait may be ahead!

So far, Chinook isn’t showing any interest in spending time in her den. We built it in one of her favorite sleeping areas. It is completely covered so no light comes in except through the doorway. We have a thermometer to keep an eye on the temperature so it stays comfortable for her. The floor is made of recycled plastic and is raised up just enough to allow for any moisture to travel beneath and into a drain. Polar bear cubs have no ability to thermo-regulate at first, so it necessary to protect them from cold but still keep the den cool for Mom.

Chinook is still making beautiful beds for sleeping. Her preference has always been Bermuda hay, but lately she is choosing pine needles we collect from around the area. Chinook is from the western Hudson Bay population of polar bears; this means the den she was born in was first dug in frozen peat with tree roots as the roof support. Her mother would then have dug a second chamber into the snow after it drifted into a deep pile outside the earthen den. Chinook’s den is built adjacent to another bedroom we have darkened, and she could use it as a second chamber. Right now, though, she prefers to sleep in another area of the building. Oh, what will our girl choose?

What happened when we first gave the bears access to the new management yard? Chinook went out when her keeper was out by the exhibit and went back in when her keeper went inside. An interesting behavior for our independent girl! Kalluk only stuck his head out and was more interested in his kiddie pool inside, but Tatqiq became queen of the hill! She explored and rubbed on the bushes and made great muddy paw prints from the pool. We give Chinook access to the yard every day. You may sometimes be able to see her in the yard from the Polar Cam. She looks absolutely beautiful with the trees and bushes alongside.

Kalluk and Tatqiq are keeping themselves well occupied out front. Tatqiq is filling the “dirty” bear role for Chinook. This is not a role that is unfamiliar to her. When she was a cub, she would get so brown that guests would sometimes ask, “At what age do polar bears turn white?” And Kalluk has commandeered all the kiddie pools. He has used them well. We have only one left that can be recognized by any original shape! We’ll have to wait until next summer to get new ones. Until then, both are now enjoying sleeping in the mulch piles and sandy beach area of the exhibit and making pillows from the palm wraps and ginger branches our horticulture department provides.

JoAnne Simerson is a senior keeper at the San Diego Zoo.

We now have video of one of Chinook’s ultrasound procedures.


Polar Bears: Quiet, Please

polar_chinook_walkingThe Conrad Prebys Polar Bear Plunge at the San Diego Zoo has been a really noisy place during the past few weeks. Yes, lots of construction, but mostly the noise is coming from the questioning. . . is she? We’re talking about the hoped-for pregnancy of Chinook! We still don’t know. ..for sure. That said, Chinook has gained over 20 percent of her normal body weight and has now slipped into the most calm, contented, beautiful mood we have ever seen in her 14, now almost 15, years. The most activity she shows is munching on her carrots while glancing over at the silly antics of Kalluk and Tatqiq and slowly dipping into the plunge pool to luxuriate and soak.

All this is very normal behavior for a pregnant polar bear. What we don’t know is if she could be experiencing a pseudo (or false) pregnancy. At this point, the only way we know to tell the difference is when we see the cubs. And before you wonder….Yes, we are beginning to perform ultrasound checks on Chinook. We really don’t know what to expect or when we might see something. It’s very reminiscent of the first time we performed ultrasound on our giant panda Bai Yun! The big difference is we’ll be looking for a fetus about the same size as a panda baby in a body currently at 650 pounds (295 kilograms)!

The preparations for the den and adjacent bedrooms are almost complete. The den is ready for installation as soon as Chinook gives the word; the bedrooms adjoining the den are closed in, darkened, and have sound protection; and yes, the camera mount for the den is ready! We don’t yet know if we’ll be able to have a live camera feed, but we’re working on that.

The polar bear management yard will be completed within the next few weeks. This yard will be the first place Chinook will take her cubs outside. The pool is designed specifically for cubs learning to swim. And, most importantly, the yard is all natural dirt. Can you imagine the pigpen lessons Chinook will give her cubs? Oh, the art of how to get really, really dirty!

Keep an eye on things, and when you see us put a hush over the area and ask, “Can we have quiet, please?”, you’ll know we are getting closer to knowing “Is she or isn’t she?”!

JoAnne Simerson is a senior keeper at the San Diego Zoo.

Watch the bear daily on Polar Cam