The red fox is mainly a hunter at dusk and at night, and it must rely mainly on hearing to find food. Red foxes turn their well-developed ears to find the direction a sound comes from. A red fox can hear low sounds very well, including rodents digging underground, and it can hear small animals it cannot see, such as a mouse under snow or hidden in leaves. A red fox hunts by moving back and forth over an area, finding food by scent and sound, and it also has excellent senses of vision, smell and touch.

Hertz (Hz) counts how many times a sound wave repeats each second, and a kilohertz (kHz) is 1,000 hertz. An octave is a step up where the pitch doubles. In a lab test, red foxes heard pure tones from 51 Hz to 48 kHz, a range of almost 10 octaves. Researchers who tested red fox hearing found its range and sensitivity combine the hearing abilities of a dog and a cat. The absolute sensitivity of red fox hearing is one of the best that has been described in mammals so far.

A red fox that is hunting a mouse can stand still and listen for it; it creeps close, the way a cat does, and then pounces. A red fox that has found a mouse launches itself into the air at a 45-degree angle and lands on it, pinning it to the ground. Red foxes are omnivores, which means they eat both plants and animals. They eat rodents and rabbits, and they also eat fruit, and voles are a favorite food. A red fox eats approximately half a kilogram to one kilogram of food each day. Red foxes help to control the numbers of rodents and rabbits, and a red fox may partly bury extra food, cover it with soil, grass, leaves or snow, and mark it with urine.

A red fox den is a hole in the earth 15 to 20 feet long, usually on the side of a knoll, which is a small hill. A newborn red fox weighs approximately 96 g (3.4 oz) and is covered with fine gray fur. Red fox pups are born brown or gray and usually turn red within approximately a month, and red fox kits open their eyes 9 to 14 days after birth. Red fox kits are nursed for 56 to 70 days, which means they drink their mother's milk, and their parents and older siblings also give them solid food. A red fox with kits usually stays within a mile of its den while the kits are growing up.

Adult red foxes weigh from 3 to 14 kilograms (6.6 to 30.8 pounds). A red fox's head and body are 45.5 to 90 centimeters (18 to 35.4 inches) long, not counting the tail. A red fox's tail is 30 to 55.5 centimeters (11.8 to 21.8 inches) long, and it is slightly more than one-third of its total length. A red fox's top running speed is approximately 48 km/h (as reported), and it can jump over obstacles as high as 2 m. Cross foxes are a color form of the red fox, with reddish brown fur, a black stripe down the back and another across the shoulders. Silver foxes are a color form of the red fox that range from strong silver to nearly black.

A red fox has a potential life span of 15 years, but few wild foxes survive more than 4 to 6 years. Red foxes mark their home ranges with scent, and how big a red fox's home range is depends on its habitat and on how much food is there. A red fox usually stays in the same home range for life; red foxes are now found in most habitat types, including places people have greatly changed. Red foxes have the widest distribution of any canid, which means they live over more of the world than any other member of the dog family.

Words to know

• hertz: waves per second
• octaves: pitch doublings
• nursed: fed mother's milk
• dusk: evening time