Often it's not the snow or cold that's the biggest hazard for zoo animals, it's the ice. In snow, hooved animals can grip the ground quite well, but ice is a different matter and a slip or a fall could be disastrous.
That's one of the reasons why the giraffes here spend most of their time indoors in winter.
"Because giraffes have a lot of surface area relative to body mass, we are pretty conservative when they go out. They can't get down the long pathway to their exhibit when the conditions are icy," Linehan said. And their bodies are simply not equipped to handle the bitter cold.
The temperature cut off for the male, Beau, and his mate, Jana, is around 60 degrees. It's no easy feat to protect a several-thousand-pound animal from the elements. But the Franklin Park Zoo built a special 45-foot-high heated barn with gauges at the top and bottom to constantly monitor the temperature. And there are Christmas trees dotting the enclosure to give the mammoth mammals something to play with during the day.
Zookeepers pay special attention to the food they set out for the animals -- adding special fiber such as beet root in the food to help the animals bulk up for the colder season.
"Our animals look a little more, um, robust than the animals in Southern Africa, in part because they have an extra little layer of fat," Linehan said.
If you love animals and you're thinking of going to a zoo, the cold can actually be an advantage. There are none of the summertime crowds, and the animals actually tend to be a bit peppier.
Christopher, the Franklin Park Zoo's lion, spent a recent morning roaring loudly and often from his perch on the heated rock -- a sound that could be heard all around the relatively empty zoo.
"He doesn't do this quite so often in the summer," Linehan said. "He's really a magnificent animal."