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Rodent Identification Guide

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Rodents are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. Rodents are mammals; in fact, around 40% of all mammal species are rodents. They are incredibly diverse and live in every region of the globe, including urban and suburban areas, where they have a reputation for being some of the most tenacious pests on the planet.

Rodents in the House

Rodents live in your home the same reason people do. Because they are a warm, safe environment to live in and raise our young. Generally, rodents prefer areas in homes that humans don’t frequent, such as basements, garages, attics, the inside of walls, or in cars. Rodents love clutter, as it offers them a multitude of potential living spaces.

While about 1,500 rodent species are known to exist, the most common rodents in the United States that cause problems are rats, mice, squirrels, voles, prairie dogs, groundhogs, gophers, chipmunks, muskrats and beavers. 

The most common pests in your house are rats, mice, and squirrels. 

Also called the brown rat, this is the most prevalent—and infamous—rat in the USA. They are large, growing to around 16 inches long (tail included—their bodies are around 9.5 inches), with males typically weighing around 1.25 pounds. Norway rats only require about an ounce of food and water each day to survive.

The roof rat typically lives in coastal and tropical climates, although they can adapt to colder weather. They are smaller than Norway rats, but usually have a significantly longer tail—the body length of a roof rat is 6-8 inches, with their tails surpassing their body length at 7-10 inches. Roof rats have black fur with pale underbellies, and large eyes and ears.

These rats thrive in the deserts of the southwest and Mexico. They are referred to as “pack rats” because they are fond of small, shiny objects, which they habitually run off with. They are on the smaller side, with a length of 12-19 inches (including the tail), and with adult males weighing anything from 11-21 ounces. Pack rats look like the quintessential rat, with long tails, large ears, and large black eyes.

From nose to tail, the house mouse measures 3 to 4 inches. They are active all year round, meaning an infestation could occur at any time. They are distinguished from young brown rats by their relatively small feet and head, and large eyes and ears.

The deer mouse (also known as the field mouse) is about the same size as the house mouse, but has a reddish fur coat with a pure white underbelly. They prefer to live in wooded areas, and often venture into human dwellings for the winter, bringing diseases like hantavirus along with them.

Native to the eastern and midwestern United States, the gray squirrel is one of nature’s most prodigious forest regenerators. It can also be a bit of a pest, especially in Europe, where they are regarded as an invasive species. The gray squirrel is grey, with a white underside, with a length of 9 inches to 1 foot.

The American red squirrel is widespread across the United States. It is easily identified by its distinctive red coloration. They are much smaller than gray squirrels, but larger than chipmunks. Red squirrels experience severe mortality during their first year—only about 20% of babies survive.

Rodent Comparisons

Rats vs Mice

There are a few notable differences between rats and mice:

  • Appearance. The most significant difference between a rat and a mouse is physical size. Rats are much, much larger than mice. They also have coarser fur, and comparatively larger heads and feet.
  • Mentality. It’s well established that rats are more cautious, while mice tend to be curious. For example, a rat will likely avoid a trap set in its path for few days, until it gets comfortable enough to approach it (this is why, when dealing with rats, it’s important to leave traps baited for a few days before setting). A mouse, on the other hand, will probably go for a trap the moment they discover it.
  • Burrowing. Mice are climbers, and generally prefer to build their nests higher up. Norway rats, on the other hand, prefer to keep their operations at ground level, and usually construct their nests in garages, basements, or burrowed underground.
  • Droppings. Since rats are larger, their droppings will be larger as well. Rat droppings are generally 3/8 inches long, with a diameter of 1/8 of an inch. Mice droppings are about half this size. Both are oblong pellets, but rat droppings have rounded tips, and mice’s have pointed tips.

Squirrels vs Rats

The single most significant difference between squirrels and rats is that squirrels aren’t nocturnal, and are therefore unlikely to make much noise at night. But there are a few other differences, too:

  • Nesting Habits. Squirrels are much more likely to build their nests outside, usually in trees. Rats prefer building their nests inside, on the ground, and close to food and water sources.
  • Tracks & Prints. Squirrels bound, leaving significant gaps between paw prints. Rat tracks have a more alternating pattern, and unlike squirrels, their tails often leave an obvious path.
  • Droppings. While both rat and squirrel droppings can be dark brown to black in color with blunted ends, they are found in different places around the home. Squirrel droppings are often found in attics or around tree trunks, while rat droppings are more common along baseboards, in cupboards, and behind large appliances like washing machines.

Signs of a Rodent Problem in Your House

  • Gnaw marks. A rodent’s teeth grow continuously, so they must gnaw on things to keep this growth in check. As you might expect, this leaves rather damning evidence. Look for gnaw marks on things like garbage cans, fences, food containers, and under porches. Squirrels sometimes chew through roof vents or attic louvres to gain access to the attic.
  • Runways. Mice and rats are creatures of habit and will follow the same route between their nest site and food and water uses. After repeated use, these paths develop dark, greasy rub marks that are accumulated from the oils and dirt on the rodent’s fur. Runways usually follow along manmade edges like baseboards.
  • Sounds. Squirrels, mice, and rats all make similar sounds if they’ve made it into your house; rustling or scurrying noises. The bigger the rodent, the louder the sound will be. Squirrels may also make rolling noises, as they roll nuts and acorns around. Pay attention to when the noise is being made. If it occurs during the day, it’s probably a squirrel. If you hear it more at night, it’s more likely to be a mouse or rat, since they are nocturnal.
  • Vocalizations. Both mice and rats communicate at a pitch that is undetectable to the human ear. However, if they are distressed, they may make squeaking or hissing sounds. Still, you are more likely to hear movement sounds than vocalizations.
  • Odors. When living in confined spaces like homes, rodents tend to produce an odor that is most often described as musky and resembling ammonia or stale urine.
  • Droppings. Look for droppings in areas that are not frequented by humans, like attics or basements. Droppings are found in the largest numbers near nesting sites.

Rodent Nests

Rodents may build nests for food storage, sleeping, and raising young. The nests of squirrels, mice, and rats look different. You can identify the rodent infestation by the type of nest. 

Rat Nest

Rat’s nests are a mess, design-wise. The size of a nest varies depending on the number of rats in the nest, but they are usually about the size of a cereal bowl. Rats use almost anything to build a nest—plants, garbage, cotton, insulation, sticks, twigs. Norway rats typically build their nests on ground floors or in basements. Less commonly, they burrow in the ground.

As their name implies, roof rats prefer to nest off the ground. Roof rats live in colonies and prefer sheltered habitats like lush landscapes, dense vegetation, and fruit trees (especially citrus trees in Florida). Inside, they prefer to nest in the upper parts of buildings like attics or rafters.

Mouse Nest

Mice often build their nests with soft, easily sourced materials such as paper, fabric, string, insulation, and mattress and pillow batting. The nests appear as rough, ball-like structures, around four to six inches in diameter. Unlike Norway rats, mice are climbers, and will often build their nests in attics. There will likely be many droppings surrounding the nest.

Squirrel Nest

Squirrel nests are much larger than rat and mouse nests. They are clumped-up assemblies of leaves, twigs, bark, and moss. These nests are more commonly found outside.

Rodent Problems

Regardless of the pest, a rodent infestation can cause a number of issues. 

  • Property Damage. Mice and rats will chew on anything they see as useful while building a nest. This can include prized valuables like books or other important documents, especially if they are stored in the attic or basement. Rodents also have a fondness for living in cars, and can ruin them by their compulsive wire-chewing.
  • Fire risk. Mice and rats sometimes build their nests in large electrical appliances, gnawing through wires in the process, which can increase the likelihood of a short-circuit or fire.
  • Disease. Rodents can carry many diseases including hantavirus, leptospirosis, lymphocytic choriomeningitis (LCMV), Tularemia and Salmonella.

Rodent Control Professionals

Rodents are noted—and reviled—for their destructive capacity, the staggering rate at which they breed, and the diseases they transmit. All these factors make banishing rodents a formidable task that might prove too difficult for the average homeowner. Therefore, it is best to call a professional service like Trutech Wildlife to address a rat or mouse problem as soon as it becomes apparent, as infestations can set in in the blink of an eye.

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