‘Bloodsicles,’ water, and mud wallowing: How Philadelphia Zoo animals keep cool in the heat wave

Humans aren’t the only ones who feel the heat.

As temperatures inched closer to 100 degrees, primates at the Philadelphia Zoo enjoyed some icy, fruit-and-veggie flavored popsicles. Elsewhere in the zoo, giant river otters might be found munching on a fish pop — a block of ice with fish in it — while big cats could be snacking on a “bloodsicle,” or frozen blood, said Michael Stern, the zoo’s curator of primates and small mammals.

These icy treats are one way that animals at the Philadelphia Zoo are keeping cool during this heatwave, which has prompted the city to declare its first “heat health emergency” of the season and is only expected to get worse this weekend. Zookeepers are also distributing ice bottles for animals to rest on, watching animals more closely for signs of heat stress, and making sure pigs and rhinos have ample mud in which to wallow, Stern said.

For zoo staff, it’s a routine they are used to in Philadelphia summers.

“There’s not much that we do extremely different on a week like this than we do on a week that it’s in the high 80s,” Stern said.

Many of the animals that reside at the zoo come from tropical climates, making them physiologically conditioned for these kind of temperatures, Stern said. As for more sensitive species, a 90-to-100-degree week doesn’t trigger vastly different zookeeping practices. But small changes can make a big difference to an animal’s health and comfort.

When the temperature reaches 90 or above, primates have access to indoor spaces, he said.

Meanwhile, the zoo’s geriatric animals — such as the world’s oldest blue-eyed lemurs — don’t have a choice if the temperature gets into the high 90s: They’re moved inside for their health, Stern said.

Zookeepers are keeping close watch on all animals for signs of heat stress, which differ by species, he said, but can include sweating, licking of body parts (in animals that don’t sweat), heavy breathing, and lethargy.

Rhinos and pigs don’t sweat, he said, so one of the ways they stay cool is by rolling around in mud wallows. During extreme heat, zoo staff fill up those wallows with a hose, Stern said, and then enjoy watching giant Tony, a white rhino, roll around like a joyful “little puppy.”

Other animals require more water or juicy fruits on particularly oppressive days, he said.

Animals “certainly can get dehydrated,” he said, “but they don’t usually need as much water as people do.”

Stern said zoo visitors can easily keep cool, and the viewing experience doesn’t change much when some animals move inside.

“We have a lot of great indoor spaces,” Stern said. “We’ve got a lot of nice trees making shade. We’ve got misters set up around the zoo.”

And as a bonus, he said, “you can see all these tropical animals in the kind of weather that makes them feel at home.”