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94

Spring Cleaning for Polar Bears

Tatqiq really enjoyed her snow day last year!

Tatqiq really enjoyed her snow day last year!

The San Diego Zoo’s polar bears will be off exhibit through today while we spruce up their exhibit a bit. Our goal is to provide a dynamic environment for the bears. It is quite the undertaking to move around all of those giant root balls and logs in the exhibit, as well as bring in new ones.

We brought in a crane to lift a 5,000-pound root ball from the elephant yard and place it in the polar exhibit. We hope to be able to do this at least two to three times a year to change up the exhibit for our bears. A wild polar bear’s environment is constantly changing due to the movement of the sea ice, and we feel it is important for our bears as well. We want them to have an exhibit and a home that isn’t always the same every time they leave the bedrooms. At this time you will also see a completely empty exhibit pool. All 150,000 gallons were drained so that we could go in to steam clean and pressure wash the entire surface of the pool. This is something we do once or twice a year.

In addition to moving around existing exhibit features and bringing in new ones, we will also be completely changing their exhibit on Saturday, May 17, by bringing in 18 tons of ice that will be run through a chipper to create snow for our bears. They will have a blast sliding down the hills, tunneling through the snow, and searching for things that we have buried. Generally the snow lasts for four to six days, but with the warm weather we are currently experiencing in San Diego, it could be gone in a day or two.

We hope you will be able to join us on Saturday, May 17, either in person or on Polar Cam so that you can witness all the fun before the snow is gone.

The Polar Bear Team

14

Tatqiq: Odd Bear Out

Tatqiq is sure to enjoy Snow Day on Saturday, May 17, 2014!

Tatqiq is sure to enjoy Snow Day on Saturday, May 17, 2014!

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

34

Spring in Air for Polar Bears

Kalluk digs a pile of snow.

Kalluk digs a pile of snow.

For those of us who live in San Diego, it nearly always feels like spring. (Sorry to those who are experiencing the polar vortex that hit a majority of the country recently!) Despite our consistent temperatures in San Diego, our polar bears follow seasonal changes similar to their wild counterparts in the Arctic.

We recently completed denning season, which normally occurs in the fall months (see Is Chinook Pregnant?). Now we are expecting to start a new cycle: breeding season! Those of you watching our Polar Cam may have noticed three bears on exhibit again. Chinook was reintroduced to Kalluk and Tatqiq after her months of requested seclusion. Chinook was showing some interesting behaviors associated with den making, but we eventually determined that she would not have cubs this time around.

The reintroduction went smoothly, and all the bears acted calmly. At first, Kalluk followed Chinook very closely while she walked around the exhibit. Then they both jumped into the pool for over an hour of play. Eventually, Kalluk was able to separate himself from Chinook, and all the bears rested in their favorite spots in Polar Bear Plunge.

Kalluk has been showing signs that he is getting ready for breeding season, such as an increased interest in sniffing Chinook’s footsteps and urine. However, Chinook is mainly acting coy and disinterested in Kalluk other than play (which certainly could be interpreted as slightly flirtatious behavior). Stay tuned as the saga continues…

Polar Bear Team

43

Is Chinook Pregnant?

Chinook, left, and Kalluk frolicked in the snow a few months ago.

Chinook, left, and Kalluk frolicked in the snow a few months ago.

Around this time of year for the past few years, the number one question we are asked by those familiar with our polar bears is “Is Chinook pregnant?” We nearly always answer with “We sure hope so, but….” Some of you may wonder why we are so elusive with our answer year after year. There are a number of reasons, none of them clandestine. Mainly, the polar bear community is still searching for all the answers. Things are complex in the polar bear world!

Did you know that polar bears have a wide range for gestation, spanning from 164 to 294 days in the wild (195 to 265 days in managed care)? If we determined possible birth on this information alone, this year Chinook could have given birth from July through September, based on when she bred with our male, Kalluk. However, we are aware of research that has studied historic data of births of wild bears and with other observations in the wild. It is hypothesized that date of breeding may not solely determine date of possible birth. Instead, it is a little more complicated than counting days from breeding time. Births generally occur between November and December, with the occasional birth outside those months even when breeding occurs in January, for example (when Kalluk and Chinook bred). Lastly, female polar bears have both induced ovulation and delayed implantation, which makes determining timing and the triggers involved difficult.

We are trying! Through research, we are continuing to learn more and more. Every other day, we collect urine samples from Chinook and fecal samples three times per week, all for hormone analysis. With Chinook’s full cooperation, we perform ultrasound exams weekly once her den is in place. (The den was set up this year at the end of September.) Through research and collaboration, we hope to gain new insights into the complexities of polar bear reproduction and give you more definitive answers in the future to the question, “Is Chinook pregnant?”

The Polar Bear Team, San Diego  Zoo

Watch the bears daily on Polar Cam.