Why Do Raccoons Wash Their Food? The Truth About Dousing

What raccoons are really doing

Watch a raccoon at the edge of a stream and you will see it pat, probe and grab at the bottom with its front paws, often while looking somewhere else. When it finds a crayfish, snail or frog, it lifts the prey, rolls it between its paws and rubs it, sometimes removing a shell, grit or other unwanted parts before eating.

To people, this looks like careful washing. In reality, the raccoon is doing with its fingers what we do with our eyes: inspecting what it has caught. Wild raccoons have never been seen deliberately carrying food to water just to dip it. That habit is mainly known from captive raccoons, especially when a pool or trough is close by.

Super-sensitive paws

The raccoon’s sense of touch is remarkable. Its front paws have five long, separate fingers, and the hairless skin on the palms is packed with touch receptors. Almost two-thirds of the area of a raccoon’s brain that processes the senses is devoted to touch, a larger share than in any other animal studied.

The palms are covered by a thin, tough, horny layer that protects them. When this layer gets wet, it softens and becomes more pliable, and researchers think this makes the skin even better at picking up fine detail. Rubbing food in water may therefore turn up the raccoon’s “volume” for touch. Raccoons can stand in cold water below 10 °C (50 °F) for hours without losing this sensitivity.

The paws also have stiff whiskers, called vibrissae, just above the claws. These let a raccoon detect an object a split second before its fingers actually touch it, which is very useful in murky water at night.

Raccoon paws are not quite like human hands, though. A raccoon has no opposable thumb, so it cannot pinch small objects between thumb and finger the way primates do. Instead, it grips things between both palms or curls its fingers around them, which is one reason why so much rubbing and rolling happens. The combination of nimble fingers and a brain built for touch makes raccoons skilled at opening shells, lids and latches.

Why captive raccoons “wash” their food

In zoos and other captive settings, raccoons often carry food to water and dunk it before eating, even when the food is perfectly clean. Studies of captive raccoons found that they douse food more often when water is close by, within about 3 m (10 ft), and when the water is arranged like a natural stream bank. Aquatic foods such as fish and crayfish are doused more often than other foods.

The most widely accepted explanation is that this is a fixed action pattern: an inborn sequence of movements that the raccoon performs even without the usual trigger. In the wild, the “search, grab and rub” routine is part of foraging in shallow water. Captive raccoons that do not need to hunt for their food appear to act out the same routine anyway. Cleaning dirty food does not seem to be the reason.

Old myths about raccoon washing

• Myth: Raccoons wash food because they have no saliva. The 18th-century French naturalist Buffon suggested that raccoons could not produce enough saliva to moisten their food. This idea is now considered wrong; raccoons swallow dry food without trouble.
• Myth: Raccoons are clean freaks. Raccoons eat garbage, carrion and food straight from the ground. They do not avoid dirt, and they do not need water to eat.
• Myth: Raccoons always wash food before eating. Most wild raccoon meals, such as fruit, nuts, insects and corn, are eaten without any water nearby. The full range of foods is described in what do raccoons eat?
• Fact: The name says “washer”. Linnaeus named the raccoon Ursus lotor, the “washing bear”, in 1758. Today the species is Procyon lotor, and many languages still refer to washing: the German Waschbär (“wash-bear”), the French raton laveur (“washing rat”) and the Japanese araiguma (“washing bear”).

What dousing tells us about raccoon intelligence

The raccoon’s sensitive hands are closely linked to its reputation for cleverness. Raccoons learn about the world largely by touch, and many classic experiments on raccoon intelligence tested how well they could open locks, latches and puzzle boxes with their fingers. Some of these studies found that raccoons could solve complicated locking mechanisms and remember the solutions for years. The research is summarized in how smart are raccoons?

So the next time you see a raccoon “washing” its dinner, think of it as a raccoon reading its food with its fingertips. To learn more about the animal, see the raccoon profile.