DENVER — Siberian tigers Yuri and Nikita at the Denver Zoo, due to mate, are suffering the most from Denver’s intensifying 95-degree heatwaves, and janitors are delivering cooling ice “goblets” from the zoo’s busy freezers.
Zoo keepers have also set up an industrial fan behind a smoke generator aimed at the polluted orange-and-black tigers. Sometimes the tigers rush into pools and collapse in an attic where there is a flow of air. Nikita flops down on a pile of wet sandbags.
Penguins enjoy “snow,” made by crushing cubes from the zoo’s ice machine, the large kind found in motels. These are penguins from South Africa and Peru that are better adapted to heat than their Antarctic relatives.
Sea lions gnaw modified versions of bloody tiger bones in blocks of ice – salmon-laced “fish”. And many animals seek refuge in the water. Zookeepers toss apples, melons and carrots for elephants to encourage them to plunge into ponds.
Four Mongolian feral horses – a species that evolved on steppes resembling the terrain of western Colorado – have proven they can withstand the scorching sun. Leopard tortoises simply bask.
But overall, the rising heat in Colorado poses challenges for zoo operators. They care for more than 3,000 animals representing 450 species, including many that didn’t evolve to endure prolonged heat — not to mention the 100-plus-degree temperatures climatologists warn are in Colorado’s future will be common.
Surviving climate change has become a key challenge for zoos around the world, as well as for people living in densely populated cities like Denver, where concrete and asphalt amplify the heat by up to 20 degrees. On the one hand, zoos play a key role in the conservation of species as natural habitats disappear or become less hospitable. On the other hand, it is becoming more difficult to provide suitable shelter.
Zookeepers in Denver could just move more animals into air-conditioned buildings.
“Yes, we could. But our animals really want to be outside. And we want them out. We want them to enjoy these outdoor exhibit areas — and be there for our guests,” said Emily Insalaco, Denver Zoo’s curator general, an animal behaviorist.
“How can we continue to offer them and our guests this environment? How do we design exhibition areas that meet all the needs of our animals? We have temperature parameters for every single species we care about. We know where they come from in the wild and what that environment is like,” Insalaco said.
“We’ve seen wild animals leaving their natural habitat and looking for better places, cooler places, places with more food. We’ve seen pollinators emerge from their winter hideouts earlier than usual and get caught up in spring snowstorms. We can learn a lot. It’s all right in front of us. We’re all in the same boat.”
Aside from frozen treats, fog, and the occasional ice bath, the zoo’s long-term strategy is to provide better shade — similar to what Denver officials say they will do to keep the surrounding city hospitable.
The zoo’s horticultural team counted a total of 7,500 trees on its 84 acres in City Park, east of downtown — a mix of mostly poplars, along with pines, cottonwoods, lindens, and catalpas. But trees are dying here, as throughout the city, due to heat, drought, and insects. Zoo officials have recently begun a tree canopy assessment and plan to increase tree planting to increase shade for the animals.
Nationwide, polar bears in zoos that once numbered in the hundreds have declined to fewer than 50, according to polar bear surveillance groups.
At the moment, the former Denver polar bear sanctuary keeps a lone grizzly bear named Tundra, who was orphaned as a cub in Alaska around 2002.
Zoo officials acknowledged that planting trees to increase shade will take years. Surviving last week’s heatwave and expected high temperatures in the years to come will require a creative and aggressive approach, officials said.
“We’re constantly trying to figure out how to make it (the tigers) comfortable,” said carnivore keeper Kim Pike.
And while gardeners prepare to plant trees, zookeepers order pergolas and canopies to provide instant shade.
They installed one this spring for the tapirs native to Malaysia, where dense jungle offers shelter.
Zebras have also been given a pergola in the space they share with Somali wild donkeys.
Two more were installed in the area reserved for bongos. “This allows bongos to choose where they prefer to seek shelter,” Insalaco said. “We want to make sure the entire herd has access.”