polar bear breeding season


Polar Bears: Back to Normal

Tatqiq sniffs the air after a good roll in the mulch this morning.

Tatqiq sniffs the air after a good roll in the mulch this morning.

It’s been a whirlwind few months for all of us at the San Diego Zoo’s Polar Bear Plunge! It began on January 2 and is only just now settling into what we all refer to as normal! On January 2, we re-introduced Chinook to Kalluk and Tatqiq. It became very apparent in the previous week that Chinook was very interested in being with Kalluk. The three fabulous bears took up together as though they had not been apart for the months we were waiting to see if Chinook would give birth. All of us who work with our bears thought now we just wait for breeding season to start. The wait was NOT long!

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.


Polar Bears: Hormones

Kalluk enjoyed snow day earlier this month.

Kalluk enjoyed snow day earlier this month.

Many Polar Cam viewers have expressed concern about our male polar bear, Kalluk, and his repetitive or restless behaviors. It is hard to see him so driven by his hormones at breeding time if you don’t see his full day. He does eat and rest, but not for the long periods of time as he does when his hormones are not driving him. He is not suffering but just supremely distracted!

The reason we suspect his focus is at the one end of the exhibit is due to the stimulation he may receive there. There is certainly more visual activity with buses and guests stopping to look at him, and the breeze comes right through there, carrying great scent stimuli. Research has shown that there are chemical similarities between many industrial aromas and reproductive hormones. It may well be that Kalluk is constantly testing the breeze in case there is a receptive female polar bear about to come join him. No one really knows how far a polar bear can smell, but no one doubts that their sense of smell is more than anything we could compare.

We know from past testing of his testosterone levels that Kalluk experiences exceptionally high levels for a male polar bear. A recent study indicates that male polar bears’ highest testosterone levels occur from the age of 12 to 18. Kalluk just turned 12, so we may have a tough time for the next few years. We did witness one day of breeding last month on the day after Chinook rejoined Kalluk and Tatqiq; she had been by herself on a pregnancy watch for a few weeks. Their reunion seemed to be more about the excitement of getting together again instead of actual estrus. We fully expect to see another breeding period that lasts anywhere from a few days to a few weeks.

Once Chinook’s hormones indicate that she is ready for breeding, and her behavior indicates she is ready, Kalluk’s attention will turn to only her. Then, as the breeding season wanes, we will get our fun-loving boy back. Polar bear breeding season can last from January to June! Until then, we have increased the amount of fat in his diet, increasing the calories he has to use. We strategically give him enrichment, especially scents, and strategically make beds for him that are in his interest zone.

Rest assured that we are monitoring him closely and responding to whatever he shows might alleviate some of his frustration. Keep watching Chinook as well; she also gives indicators, although much more subtle, of her breeding season!

JoAnne Simerson is a senior keeper at the San Diego Zoo. Read her previous post, Polar Bears: Exam for Tatqiq.


Polar Bears: Dare to Hope

Chinook gives Kalluk's scruff a playful tug.

We’ve all experienced wanting something so bad that it hurts. People will tell you all kinds of things to make the waiting a bit less painful. You begin to fill your head with all the knowledge you can to know if it will really happen or not. And then comes the superstitions: don’t step on a crack, don’t talk about it, fingers and toes crossed. But no matter what, it just takes time to get the really special things that you want! What am I talking about? Wondering if polar bear Chinook is going to have cubs, of course! Is there anything else on our minds? Dare we hope?

As you know, Chinook and Kalluk marked Valentine’s Day 2011 by marking the start of the polar bear breeding season. If you were to ask Kalluk, he would tell you it was a successful season. The good news is that Chinook did not go back into season. This is very good, as we believe that when a female polar bear ovulates and there is fertilization, in most instances she will not cycle again that year. This is a good knowledge point.  Chinook, as many of you have observed, has also been putting on weight. This would not be due to carrying cubs, as they are barely over a pound at birth, but would make sense that her metabolism would compensate to hold as much as possible to nurse and provide for cubs—another good point of knowledge.

Polar bears experience delayed implantation, so we would expect to see Chinook changing behaviorally once the fertilized egg implants, around 60 days before birth. Yes, she is beginning to seclude herself away from Kalluk and Tatqiq. If gestation is 195 to 265 days for a polar bears, then from the 10 days of breeding, Chinook would be due between August 28 and November 16. Panic—it’s already September! Breathe, breathe. With such a long gestation, she could be implanting right now with a due date of early November.  Most polar bear births in North American zoos have occurred in the first week of November, the earliest was on October 13. Good things to know!

We have been collecting fecal samples for hormone analysis with the research branch of the Cincinnati Zoo and urine samples for hormone analysis with the Memphis Zoo. So far, nothing conclusive from the urine analyses, but the fecal analyses look positive for pregnancy. . .or pseudopregnancy. BUT—and yes, a big but—Chinook’s hormone profile is consistent with profiles of other polar bears that have given birth! Dare we hope?

So with knowledge in place, we’re avoiding walking under ladders, stepping on cracks, saying anything to jinx it, and above all, fingers and toes crossed. You better believe we are daring to hope that this time will be for sure!

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


Polar Bear Spring

Kalluk refocuses his energy.

Spring arrived at the San Diego Zoo’s Polar Bear Plunge a few days early this year. Chinook and Kalluk began breeding on March 17 and then abruptly stopped on March 24. Last year, the season lasted from February to June! Although it’s possible we could see more, we are not expecting it to be likely. Chinook’s behavior gives us no indicators like last year that she will cycle again, and even though Kalluk has shown some behavioral frustration, he has not shown any interest in Chinook for almost a month. So what could this mean?

First, we really don’t know exactly what happens in polar bear reproduction. We do know that breeding season happens in the spring, typically March through May. It is strongly suspected that female polar bears are spontaneous ovulators, meaning they will ovulate only when breeding occurs. It is also suspected that she will not cycle again if, in a breeding season, fertilization occurs. This has some evidence to the contrary, as we do know of some cubs in the wild that share different fathers!

For argument’s sake, let’s agree that for females their breeding season ends with a fertilized egg. That would mean that Chinook has a blastocyst or two floating around in her uterus waiting to implant! Remember: polar bears have delayed implantation, giving them a gestation of 195 to 265 days, so we’ll be anxiously waiting until sometime between October 1 and December 9 this year…unless we see a return in Chinook’s interest to Kalluk. Sigh! Yes, we do plan to do ultrasound checks on Chinook as we get closer to October, so perhaps we’ll get an earlier clue. We are so lucky to have the world’s only polar bear trained for ultrasound procedures! (Watch video of an ultrasound session with Chinook from 2009.)

Kalluk also is beginning to show less anxious pacing than we normally see during breeding season. Although afternoons seem to bring about some surges, he is beginning to play and eat like his true self. During breeding season, he is so distracted we do all we can to get a few pounds of food into him. Currently, he is consuming up to 50 pounds a day. Yes, he is on his way back!

Tatqiq has had an easier time this year as well. Last year, Chinook kept her sitting up by the waterfall every day. Even though we always gave Tatqiq a choice to stay in the bedroom area, she always wanted to go out. This year she definitely gained some self confidence and became our little savvy politician and was granted privilege to use the entire exhibit.

All three bears love their new “polar bear park” (see post Polar Bears: The Countdown). It used to be that the San Diego Zoo was famous for its green polar bears, due to algae growing in their hollow hair follicles. We’ve not seen that for many years now with our improved water. But now, with the long, lush grasses of the polar bear park, our beautiful white bears are experiencing green grass stains from rolling on the knolls and down the hills! Chinook had the most lovely green cheeks yesterday morning.

This week will also bring changes to the neighborhood: our long-awaited Arctic foxes will be moving in. Arctic foxes have a very strong aroma! It will be quite interesting to watch Chinook, Kalluk, and Tatqiq as they check out their new neighbors, first by aroma and then by sight! I’m sure we’ll have photos up once the foxes settle in. Keep a look out!

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


Polar Bears: Crash, Slurp, and Shadow

Kalluk, left, and Chinook

Could it be we are nearing the end of our fantastic remodel of the Conrad Prebys Polar Bear Plunge at the San Diego Zoo? Anyone who has remodeled their home knows the joys and dilemmas that improvement brings. Most of the work that impacted our bears was completed last fall with the building of our management yard and the experience wall.

The bears love the wall area, and with all the great rain we’ve had, the yard is thick with green grass. In fact, we’ve begun calling the yard Polar Bear Park! We did, however, want to do some remodeling in the exhibit: remove some of the deadwood to make viewing easier. We set about renting a huge crane to come and lift the wood out and move the huge root balls, but…

The project started when we brought all three bears in for the afternoon and night while we cut through all the metal thread that held everything together, cut the wood into smaller, more manageable pieces, and basically prepared all for fast work the next morning. Everything needed to be done by 9 a.m. so the crane would not block the road.

We were all in an hour early; we made sure the bears were all fed and happy with new beds or enrichment and then set up for the crane. The crane arrived early but, OH NO! The hydraulic line broke! The crane was out of commission. Now what? We can’t let the bears on exhibit—it was too dangerous with all the loose logs. In steps teamwork!

One of our animal care managers got a bobcat tractor while ropes, chains, pry bars, and determination were gathered. For the next two hours logs were pulled off and out with loud crashes and moved into better positions. The polar bears’ “living room” took on a whole new look. By 9 a.m. we had everything done and secure so our trio could come out and assess our work. We expected lots of curiosity from them, but they took a look, a sniff, and went off to their carrot piles! We will be doing a bit more work before the grand re-opening on March 26, including removing one more root ball and filling part of the center shelter area with sand for another sleeping area.

There is also a return of that wonderful “sllluuurrrrrrpppppp” sound every day from Kalluk. What does this mean? As we are beginning to understand, scent is an integral part of polar bear communication. Just as breeding season begins, Kalluk busies himself with smelling everywhere Chinook has stepped. He flattens his nose and mouth to the floor and slurp-inhales with all he’s got to assess where Chinook may be in her approach to breeding season. We now are seeing him less and less away from her as he has become her shadow. This year, he seems to be less anxious about it, perhaps after last year he has gained some maturity and confidence. In the past few days we have begun to see Chinook become more flirtatious with him, and she often adds a nice face rub to her greetings to him. She rarely goes anywhere now without her 1,000-pound shadow!

Tatqiq is beginning to be an outcast, but she also seems to have gained some confidence. She is not backing down from Chinook but instead stands in place and offers behaviors that neutralize Chinook’s advances. Every day we do offer all our bears the opportunity to show us what they need, and so far everyone still wants to be together. We are really happy that when it comes time to give someone a break, they get to spend it in the new Polar Bear Park!

When you come to visit after re-opening on March 26, you will be able to see through the exhibit and look on the hill and see our bears in their lush, green park.

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

Watch video of the new statues and interactive elements being moved into place at Polar Bear Plunge.