The scene is iconic, probably something you’ve watched at some point on video or a television show. It’s a snow-covered winter landscape with a red fox, perfectly still, ears flicking slightly, body tense, head facing the snow. Perhaps the dulcet voice of host BBC Earth’s David Attenborough or Wild Kingdom’s Marlin Perkins explains that the fox is hunting, listening for the rustle or squeak of a mouse or vole.
Then ... the fox springs upward, catapulted by its small but strong hind legs and hips. It falls headfirst and disappears halfway into the snow, bushy tail aloft and legs kicking. It re-appears, face and front shoulders dusted in white. Within its sharp teeth is a small animal, much-needed fuel to battle the cold. The fox will repeat this process six or eight times a day, seeking enough nutrition to get through a cold night and the next day.
This process is called mousing. That makes sense since foxes eat a lot of mice, rats, voles and other rodents. Under the beautiful layer of snow can be a little world of activity. Time for a quick science lesson: When snow reaches about 6 inches or more, and there is no permafrost, temperatures in this subnivian zone at the snow base may be about 32 degrees or so. The ground isn’t frozen solid, and the snow creates a layer of protection. Rodents must eat in winter, too, and will take advantage of this sort-of-warm layer to create tunnels, scurry about and forage for seeds, grasses, bark, mast and other foods.
If you’ve seen this mousing activity on a show or video, no doubt the first time a thought popped up: How do they not smash their face in the snow or ground?
Smart Hunters
That’s a good question, of course. But foxes are smart. Not all snow is powdery soft, although foxes don’t dive like Olympians into glazed ice. They’re adept at hunting in the best conditions. Powdery snow is layered and has teeny air pockets. Scurrying rodents can be heard through the snow, thanks to a fox’s large ears (relative to its head). Similar to a deer’s ears, these cupped wonders pick up noisy skitters and scatters of tiny mouse feet or squeaks through the snow. And, if the snow is only 6 to 10 inches deep, a fox simply may pounce and dig instead of diving.
But yes, when a fox dives, its snout leads the way for its head, ears pinned back, streamlined like a furry reddish missile. When it comes up, possibly with a snack, its face doesn't look like an accordion or Looney Toons character.
Sunghwan Jung wanted to know how this happens. Jung is the Professor and Director of Graduate Studies for Biological and Environmental Engineering at Cornell University in New York. He and his team decided to find out how a fox survives the dive. Team members included Jisoo Yuk, Anupam Pandey, Leena Park and William E. Bemis.
First, Jung and his team scanned the skulls of 13 fox species in museum collections. They also included the skulls of some other predators including lynx and pumas. Both cats have a tremendous sense of smell, aggressive behavior when securing food, and may smash a snout on occasion when securing that food. Of the fox skulls, Jung’s team determined that red and Arctic foxes have skulls that differ slightly from their fox cousins. Not all foxes are mousers, either.
Fox snouts and heads are more streamlined. Remember the ears? A fox facing in the direction of a sound perks its ears (like a whitetail deer). The sound waves travel toward the slender, streamlined snout and face and into those big ears. Their skulls are more pointed. This means they don’t have as strong of a bite like a mountain lion, lynx or bobcat. Those predators have more compact, wider, smushed faces and skulls with bigger muscles and more per-pound pressure on the bite.
Jung and his team made 3D models of an Arctic fox skull and a flatter version of the skull. They dropped them into snow from 50 centimeters, or about 20 inches. In comparison with the 13 fox species they scanned from the museums, the researchers found that Arctic and red fox muzzles were slightly more elongated than others. In the snow, that slight change helps get through the powder easier and prevents a smushed snoot.
“What we found was that the sharper snout reduces the impact, by compressing the snow less,” Jung told New Scientist magazine in 2024. “This kind of elongated shape helps foxes dive into snow safely, so they can focus on hunting.”
Jung reported that “the curvature of the snout plays a critical role in determining the impact force, with an inverse relationship. A sharper skull leads to a lower average impact force, which allows foxes to dive head-first into the snow with minimal tissue damage.
Also: “Impact force into snow is modeled using hydrodynamic added mass during the initial impact phase. This approach is based on two key facts: the added mass effect in granular media at high Reynolds numbers and the characteristics of snow as a granular medium. Our results show that the curvature of the snout plays a critical role in determining the impact force, with an inverse relationship. A sharper skull leads to a lower average impact force, which allows foxes to dive head-first into the snow with minimal tissue damage.”
Hardy Animals
Foxes hold a special place in the pecking order of predators and varmints. They have a tough canine background, but not as much brawler attitude as coyotes, wolves or the more slinky feline fighters.
All will scamper away, usually, when encountering humans or another animal threat. A fox isn’t going to stand up to a wolf, for example, over a dead deer. It’s not going to play scratchy-bitey with a lynx or mountain lion. Territorial disputes might end with a coyote or feline killing the fox, which it sees as a nuisance. But a fox might pin its ears back and get feisty if it feels it can do so against an opponent. Disease, such as rabies or distemper, always puts these canines into a different realm. Hunters and homeowners should be aware of any wolves, foxes or coyotes acting strangely.
About 25 years ago, we lived in a neighborhood slashed into a wooded hillside. I worked late nights at the time, and occasionally when I arrived home about 1 a.m. I’d see a fox trotting along the sidewalk. First thought? Cool critter! After three or four sightings, it wasn’t afraid and clearly was out hunting. One night, with no traffic on our neighborhood street, I stopped and rolled down my truck window. The fox stopped and sat on the sidewalk facing me, like a dog. It was weird. No foamy mouth or anything, but its comfort was unnerving.
Foxes and coyotes adapt, and during winter they work to survive. Both have breeding seasons from about January to March. Coyotes make dens, and foxes may curl up on the snow with its big fluffy tail wrapped around for warmth. If it gets snowed on, like a deer, it stands and shakes and moves along. They hunt for varmints, rodents, small game, whatever’s available. Despite appearing fragile, foxes are wary and tough.
The research by Jung and his team might not help you hunt or trap more foxes. But it’s interesting. Foxes are found around the world, were scientifically named by Carl Linneaus in 1758 and have DNA ancestors dating more than a million years ago. Who knew that only a couple of the fox species were mousers? I didn’t and have been a biology-animal junkie for decades. Learning something new is fun.
If you’re sitting around with your kiddo or grandchild, put on a video of a fox mousing in the snow. Explain what they’re doing and why they don’t smash their streamlined faces in the snow or ground. Pass it along and help the next generation learn something cool and new.
