Polar Bears: Keeping Cool

Tatqiq knows how to stay cool!

The summer of 2012 will go down in history as one of the hottest on record. This brings lots of questions as to how polar bears at the San Diego Zoo can live in even the milder heat here. The first answer: our 130,000-gallon (490,000 liters) pool is chilled to under 55 degrees Fahrenheit (12 degrees Celsius). The shallow area allows the bears to lie down and even sleep if they choose. The mid-range allows for great soaking opportunities, and the 12-foot (3.6 meters) deep end allows for complete submersion and swimming. On most summer days, the breeze through the exhibit comes right off of San Diego Bay, so it is a cooling sea breeze. Throughout the exhibit there are numerous shaded areas with various bedding materials for the bears to sleep on. There is also a portable air conditioner we can direct up by the back area where they especially like to sleep. Inside the bedroom area, we also have air conditioning to take the heat out if absolutely necessary.

The real reason we can keep our polar bears comfortable, even on the hottest days, is by limiting the amount of fat they have on their body. For polar bears to survive the cold of the Arctic, they must build up at least 4.5 inches (11 centimeters) of fat over their body. They do this by eating seal blubber. A polar bear’s diet is 90 to 95 percent fat in the wild. They are so specialized for eating fat that they metabolize close to 90 percent of what they eat into body fat.

Here in San Diego, our nutrition staff has developed a diet that is 5- to 10-percent fat, so our polar bears get what they need for good health but not for bulking up for a cold winter. All of our bears would weigh much more than they do now if they had those fat layers. Kalluk, who is now over 1,100 pounds (500 kilograms), would probably be closer to 1,600 pounds (725 kilograms)! When polar bears put fat on, it goes first on their belly to protect their core. Do you know that the body temperature of a polar bear is the same as ours? 98.6 degrees Fahrenheit (37 degrees Celsius)! The fat then layers over their bum and spreads out over their body.

Here’s one way to tell our three apart: When you look at them in profile, Kalluk and Tatqiq have a rounding of their bellies, but from the top of the hip to the tail it’s flat. Since we keep a bit more weight on Chinook (just in case she might be pregnant), her belly is nice and round, and her bum matches! And let’s not forget the CARROTS! Polar bears get little to no nutrition or calorie from vegetation. Our three can eat as much as they like and not put on a pound. Currently, they get 100 pounds (45 kilograms) a day between them that gets chewed, swallowed, slightly steamed in their bellies, and then eliminated. As keepers, we call that job security!

One problem with warm weather we seem to be challenged with this summer is the algae growth. Our water quality team constantly monitors the pool’s water for safety and cleanliness, but algae is airborne until it finds moisture. With the warm temperatures and direct sun, we’re experiencing quite a bloom. We add rock salt to help, but, unfortunately, some of it has imbedded into Tatqiq and Kalluk’s hollow hair shafts. It sneaks in through the small breaks in the shaft formed by grooming. This won’t harm them in any way, but it’s pretty embarrassing to have polar bears with a greenish hue! Our polar bears were once famous for being green when they lived in the smaller grotto exhibit decades ago. Since moving to this exhibit in 1996, we’ve not had any “greening,” until this year. So in the next few days we’ll be hosting “spa days” for a purpose—mineral salt-water soaks for all! Chinook and Tatqiq have always been pros at the soak; Kalluk will be challenging, since he thinks it’s only about dive bombing his sister and then slurping the saltwater off his giant paws. He’s got 13 inches (33 centimeters) on each foot to slurp from!

Summer brings great fun but also great danger with the dry heat. It is sad to hear of fires burning across our nation, so many losing their homes. It’s heartbreaking to lose so much; thank goodness for insurance. In the past few decades, polar bears have lost their ice homes in an area the size of Texas and Alaska combined. We now see forest fires burning in the Canadian tundra, the place with one of the highest densities of polar bear denning, the place where our beloved Chinook was born. What insurance do they have? They have us. We must be the guardians of our planet. We must continue to reduce our greenhouse gas emissions, especially when it seems there is no hope. We still know it can be done. We must be the insurance to protect and insure that our children and grandchildren will still have the opportunity see the magnificent polar bear roaming our planet.

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

Watch the polar bears daily on Polar Cam.

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