Red Fox: Magnetic Hunters of the Northeast

A red fox hunting near Terrace Spring, Yellowstone. NPS / Neal Herbert.

Famous for their cunning, red foxes are as much at home in wilderness as in a subdivision. They have the largest range of any land mammal except humans. Though the largest of the "true foxes," they're surprisingly small: males ("dogs") average about 11 lbs and females ("vixens") 9 lbs — less than a big house cat.

Not always red

The usual coat is red, with black legs and ears and a white belly and tail tip — but not always. Coats are often darker at high latitudes and in winter. The cross fox has a black face, a mixed red-orange coat and black stripes down its back and shoulders; there are all-black foxes and "silver" foxes with silver-tipped guard hairs. So variable is the species that it's split into at least 45 subspecies. Vulpes vulpes fulva, one of nine in North America, lives in the Northeast, with a shorter snout, wider feet and longer fur than its European cousins.

Old and new

Before Europeans arrived in the 1600s, red foxes lived only in boreal and western mountain North America, and they weren't common on the East Coast until the mid-1800s. A popular story blames fox hunting: the native gray fox, smaller and shyer, escaped hounds by climbing trees, so hunters imported Old World red foxes. Today's eastern red foxes likely descend from both those imports and native foxes that spread as forests were cleared for farms.

A magnetic pounce

• Winter hunting: meadow voles and mice, active by day under the snow, draw foxes out in daylight too.
• Hearing: foxes hear both low sounds like nibbling and high ones like squeaks under several feet of snow — perhaps the widest hearing range of any mammal, matching dogs at the high end and cats at the low.
• The leap: having pinpointed prey, a fox leaps in a high arc, steering with its tail, and plunges head first as far as 16 ft away.
• The magnetic surprise: a Czech study published in 2011 watched 84 foxes hunt over 2 years. In deep snow or tall grass, jumps aimed roughly north-northeast succeeded 73% of the time, and those aimed the opposite way 60% — but all others only 18%. Foxes may use magnetoreception, sensing Earth's magnetic field. They tilt their heads and swivel their ears as much as 150 degrees to locate prey up to 100 feet away under 3 feet of snow, then align about 20° clockwise from magnetic north before jumping. In short grass or shallow snow, where prey is visible, they show no preferred direction. Red foxes are so far the only animal known to use magnetoreception to hunt.

A red fox on a trail camera, Big Thicket National Preserve. NPS.

Eyes that shine

• Amber eyes may reduce glare, as in some squirrels, when hunting on bright snow.
• Vertical pupils, like a cat's, close tighter than round ones; with horizontally closing lids, they let foxes hunt in any light.
• Night vision: behind the retina, the tapetum lucidum ("bright tapestry") reflects light back through the eye, doubling the light available — and making the eyeshine seen in headlights: yellow-orange in adults, blue-green in shorter kits. Humans lack it, which is why our eyes flash red in photos, lit by the blood in the retina.

Scent marking

Foxes mark stumps, fence posts, rocks and trail junctions with urine and scat, revealing sex, status and even identity. In the mating season — usually February in the Northeast — male urine turns musky and skunk-like, about one-third volatile sulfur compounds. Boundaries are usually respected, and fights are more ritual than rage, except when young males disperse, food is scarce or mates are hard to find. Foxes may mark up to 70 times an hour in rich hunting grounds, defend favorite ones fiercely, and barely mark at all where food is plentiful and neighbors few.

More

Watch a red fox pounce on voles in deep snow, and read a 2020 Rutgers paper on red foxes' effects on native biodiversity.

Sources

Based on "Species Spotlight - Red Fox," Northeast region parks including Acadia National Park and Marsh-Billings-Rockefeller National Historical Park, National Park Service; a work of the United States government in the public domain. The source's photographs, credited to an individual, are replaced by public-domain NPS Gallery photographs from Yellowstone and Big Thicket.