May/10

4

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 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.

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