How Chicago's zoo animals stay warm during cold, snowy winters

CHICAGO — A chilly Chicago winter doesn’t necessarily mean the African lions at the Lincoln Park Zoo have to go inside. In fact, as temperatures dip — even as cold as 10 degrees or in the snow — the pride may huddle up on heated rocks in their exhibit to spend more time relaxing outdoors.

“They also have access to indoor holding areas in the winter, so if they want to go into a space that’s completely enclosed and warmer, they can go in there whenever they like,” said Dave Bernier, the zoo’s general curator. “We give them the choice, and luckily, they choose the exhibit spaces a lot more than they choose the holding spaces.”

Lions aren’t the only species that are better equipped for the winter than one might expect. Specialists at Chicago’s zoos say they use a combination of technology and habitat features to prepare months in advance to properly care for every animal with unique requirements for the season, from polar bears to koalas to flamingos.

The Lincoln Park Zoo prefers to find species that can be outside for the four seasons, based on their temperature guidelines, Bernier said. But, like for the lions, which are found in sub-Saharan Africa, where temperatures usually range between 65 to 85 degrees, there’s a bit of creativity involved to give them a boost in the winter.

The lion exhibit, Bernier said, has about 20 of the heated rocks, which have a surface temperature between 55 and 60 degrees. He said the zoo determined the size and placement of the rocks — which helped make them as comfortable as possible — using behavioral data from the previous lion exhibit. There’s also an overhanging shelter so the lions can escape the rain or snow, and they can head inside to a holding area if they want to, he said.

Some animals require a bit more oversight, however, including the two male koalas named Brumby and Willum at Brookfield Zoo Chicago. The fuzzy animals, which are native to Australia and made their debut at the zoo this summer, are allowed outdoors only if it’s above 40, said Mark Wanner, the associate vice president of animal care and conservation.

Unlike most other mammals, a koala has a smooth surface on its brain, meaning it’s unable to draw conclusions or make simple decisions. This means that the zoo staff keeps a close eye on the duo when it’s between 40 and 60 degrees, because the koalas can’t always choose themselves to head inside.

“Their cognitive ability is not quite what it would be in a lion, so to speak,” Wanner said.

When it starts getting cold out, Wanner said, specialists decide day by day whether it’s safe for various animals to be outside. The wind is also a big factor, he added.

“We tend to err on the side of caution, because we do get such drastic drops in temperature and such extreme temperatures here,” he said, adding that some animals, such as brown bears, grow additional hair or fur during the winter to cope with colder weather.

To monitor surface and ambient temperatures, humidity and wind speeds, the zoo uses a tool called a “thermal neutral zone kit,” Wanner said. Employees point it at an animal’s habitat to track thermal zones, checking, for example, whether a rock is putting off a sufficient amount of heat. The zoo also has temperature sensors installed in buildings that notify the staff if something goes awry, he said.

Both zoos start “weatherproofing” for the winter around September, including switching on heating elements and, at Lincoln Park, a snow melt system for the penguin exhibit. Brookfield employees lay out extra bedding for some animals inside their indoor habitats, what Wanner called their “bedroom,” and make sure water lines are protected.

On the flip side, the zoos provide fans, ice and cooling areas to some animals in the summer, such as polar bears and gorillas.

Bernier said it’s important to find animals to bring into the zoo that are the right match for Chicago’s climate. When the Lincoln Park Zoo opened the Pepper Family Wildlife Center, it opted to bring in the Canada lynx and snow leopard, rather than an ocelot or margay, small carnivores that live in tropical climates, because they wouldn’t have been able to handle the winters, he said.

Snow leopards, which are large cats that weigh up to 120 pounds and found in central Asia, can be outside when it’s below freezing. But Bernier said the animal care team may consider bringing them inside for short periods of time if it hits 20 degrees. It’s one of the “hardy” species at the zoo that are actually suited to cool climates and are quite active during the season. Others include the red pandas and Sichuan takins, as well as the Mexican gray wolf at Brookfield.

Lincoln Park Zoo’s plains zebras, which Bernier said are found in very far southern Africa and experience more seasonal rather than temperate climates, can be outside almost all year round in Chicago. The zoo also chose African penguins rather than Antarctic ones, so they don’t have to be kept cool through refrigeration all year. Their pool is heated in the winter and cooled in the summer, he added.

The animal Bernier said visitors are usually the most surprised to see outside in the winter is the pink flamingos. The zoo is home to Chilean flamingos, which are smaller, live in high altitudes and can tolerate extreme temperatures — even well below freezing — much more so than the Caribbean kind, which Bernier said the zoo once owned and had to put inside a building for half the year.

Bernier said the winter is a “fantastic” time to visit the zoo, and that some of his favorite moments are watching the rhinos and polar bears play in the snow.

“They like to be out in the snow, and it’s kind of fun to watch them roll around in the snow and see how much they enjoy that kind of weather,” he said.