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.

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