Rodent Facts

Learning about rodent facts is crucial to effectively manage commensal rodents. Their historical path is marked by epic horror, destruction, and devastation. From the plague to modern structure fires and economic losses, rodents have their place in nearly every part of human history.

Since 1978, we have been providing our customers with rodent-free lives throughout Kentucky, Tennessee, and Virginia. Regardless of the species, rodents pose several threats to humans and are often best left to professionals for proper and safe control.

Below are the most common rodents in Kentucky and surrounding states, along with important information to help educate oneself about rodents and their habits, biology, dangers, and prevention measures.

Deer Mouse

Scientific Name: Peromyscus maniculatus
Color: Dark to light brown back with a white underbelly and feet, and a bi-colored tail (brown top and white bottom)
Tail: 2-3 inches long, bicolored, brown on top, white on bottom
Size: 3 – 5 inch body (Sizes vary depending on variety)
Characteristics: Large eyes, rounded ears, long hind feet, white underbelly
Region: North America
Food Sources: Seeds, fruits, nuts, insects. Omnivorous

More Info: Check out our Deer Mouse vlog.

Threats:

Can be aggressive when raising young
Damage to structures, furniture, clothing, bedding etc.
Agricultural crop damage including seed crops, almonds, avocados, citrus, pomegranates and sugar beets
Hantavirus Pulmonary Syndrome (HPS)

Habits:

Highly sociable
Often gather in groups with a single male, multiple females and their offspring
Known to “huddle” in groups of 10 or more in cold months
Undergo daily torpor in winter
Primarily a ground-dwelling rodent but is also an established climber
Build nests by burrowing into the ground. Also build in stumps, logs, tree cavities, brush piles, bird nests and human dwellings, or other structures
Typically nocturnal
Spend most of their time near nests or food caches
Important disperser of seeds and spores within their native range

Reproduction and Lifecycle:

The deer mouse is often polygynous (males mate with multiple females), but can also be polygynandrous (both sexes having multiple mates). Breeding can occur at any time during the year, however, during warmer months breeding is at its peak. Once the female has given birth, she may be bred again while her offspring (kits or pups) are still suckling. Gestation periods generally last 22-25 days when the female is not acting but can last 24-30 days when lactating. Litter sizes vary from 3 – 11 and average 4 – 6. The offspring are born altricial but develop quickly. Their eyes open at around 15 days, they will be weaned by 25 – 35 days, and reach sexual maturity at 35 days for females (does) and 49 days for males (bucks).

Nests and Colonies:

Deer mice are said to be typically solitary except during mating season and in winter. The mating season stretches from March to October, and the remaining months are considered winter months. It may then be said that deer mice are social. Depending on what scientific study you read, you may get either of those answers. We simply chose to narrow it down to the facts; deer mice may be social or solitary, according to scientific studies.

Often, deer mice nest in groups, especially in winter. Nests are often found in elevated locations, are messy, and cup-shaped. They may be crafted from a variety of locally-sourced materials from fur, feathers, hair, plant fibers, paper, thin plastics and other readily available items. Different species of deer mice prefer different nesting locations based on their environment.

Their populations are quite common in their native range and typically prosper well. However, cold winter seasons can lead to starvation with a relatively high rate of mortality. Their population numbers have not been measured and remain unknown, but remain stable and are classified as (LC) Least Concern; meaning they are not endangered.

There are roughly 60 different species of deer mouse ranging from Canada to Central America. These may live within forests, grasslands, shrublands, deserts, islands, and mountains. Their primary predators are hawks, owls, foxes, snakes, coyotes, weasels, cats, and more.

Snakes will feed where deer mice are prominent. Homes and businesses near areas where deer mice are found may be at risk for infestations of deer mice and predacious snakes. When deer mice infest structures, nesting may occur. Due to their nesting habits, several mice may be found nesting together, potentially causing serious damage to homes, businesses, personal property and other items. Additionally, when larger infestations occur, the potential for Hantavirus Pulmonary Syndrome is present.

Preventative Measures:

Ensure other pest populations and dead insects are not accumulated within the structure.
Reduce or remove items from your property that meet their diet (such as seeds, nuts etc.)
Eliminate or reduce entry points to the structure
Remove nesting materials inside and outside the home when possible
Store foods that meet their diet criteria in airtight containers.
Don’t leave foods open, especially pet foods
Eliminate moisture and standing water from around the structure.
Keep all shrubs, plants, and trees at least 16” from touching any structure surface.
Maintain a well-kept lawn, including weed trimming
Keep up with continued home and property maintenance
Utilize habitat modification on your property to reduce conducive conditions
Employ regularly scheduled rodent control by your pest control company of choice
Learn the signs of mice

House Mouse

Scientific Name: Mus musculus
Color: Gray to light brown and black in the wild. Domestic house mice vary from champagne to black including multi-colored. House mice are agouti colored. Some sub-species sport a light colored underbelly.
Tail: 2-4 inches long and nearly hairless
Size: 3-4 inch body
Characteristics: Pointed snout, large rounded ears. Have sharp notch in upper front teeth. Short hind feet. Short hair.
Region: Throughout the U.S, parts of Canada, Mexico and many other parts of the world
Food Sources: In the wild: seeds, insects, carrion and various plant matter. Omnivorous.

Threats:

Consume and contaminate foods meant for humans, pets, and livestock
Create significant economic losses globally
Destructive to structures and personal belongings
Pose the threat of structure fire by chewing wires
Carry and/or transmit a variety of illnesses and diseases. Learn about these adverse effects.

Habits:

Social behaviors are adaptable to their environment
Depend heavily upon humans and generally do not survive well outside of human settlements
Mostly nocturnal but sometimes diurnal
Are good jumpers, swimmers, and climbers
Rely on pheromones for communication. Both sexes produce pheromones from the preputial glands. Males additionally produce pheromones in their urine and tear fluid. Pheromones are detected by both sexes through the use of the Jacobson’s organ (vomeronasal organ)
Primarily polygamous but can also be monogamous
Highly territorial, especially in the wild
Rarely move more than 30 feet from their nesting site unless food is scarce
Prefer seeds, grains, and foods high in fat and protein, such as nuts, bacon, butter, and sweets
House mice are considered “nibblers” and will make several trips in a single night to find food from various available sources

Reproduction and Lifecycle:

Reproduction can occur at any time of the year and usually begins with the male “courting” the female. This “courtship” may last several days and will include the male calling to the female, following her, and sniffing her. Once mating has occurred, the gestation lasts roughly 19-21 days, at which time a litter of 3-12 young may be born (typically 4 – 8). The female may produce 5 to 10 litters per year, allowing reproduction to occur rapidly.

The pups are born blind, hairless, and without ears. By the fourth day, the ears are formed and visible. By the sixth day, fur begins to appear. At 13 days old, the eyes will open, and by 21 days, the pups will be weaned. Females will then reach sexual maturity at around 6 weeks old, and males at around 8 weeks. However, both males and females may begin breeding as early as 5 weeks old.

Nests and Colonies:

Inside human settlements, the house mouse nest will consist of a variety of available materials. Candy wrappers, insulation, paper, clothing, string, stuffing material, and just about any other soft material will do. Nests will be messy and seemingly accidental, unlike neatly prepared bird nests. However, while the nest may seem messy, there is a strategy to their nests. Furthermore, the nesting sites can help determine whether the mice are thriving well or barely surviving. Well-prepared nests with multiple materials spread nicely to form a soft bedding for the offspring indicate a successful mouse. When very little material exists, only one kind of material, or no material at all, the mice are not surviving well.

Typically the house mouse will nest individually. Among human dwellings where populations are heavy, several may seemingly nest together. A good place to find a nest is behind an appliance, close to a heat source, inside the walls or cabinets, in the attic, in furniture, and other similar areas. Damages from nesting mice can range from chewed electric wires to plant damage and include the potential for insulation damage, drywall damage, food contamination, and more.

Preventative Measures:

Seal foods in secure packaging
Keep kitchen and food areas clean
Keep garage doors functioning properly and avoid allowing gaps and cracks to form in the seals
Maintain a decluttered and clean garage
Avoid stored or stacked items outside
Discard garbage daily at least, including cardboard boxes
ALSO SEE PREVENTATIVE MEASURES under DEER MOUSE above
Learn the signs of mice

Northern Short-Tailed Shrew (Not actually a rodent)

Scientific Name: Blarina brevicauda
Color: Black, brownish black, or silvery gray. Ventral fur is lighter and more gray.
Tail: Short
Size: 4 – 5.5 inches long (Northern short-tailed is the largest in North America)
Characteristics: Pointed snout, hidden ears, tiny eyes, short and slender legs, cylindrical body
Region: Northeastern to central U.S. and parts of southeastern Canada
Food Sources: Insects, earthworms, snails, voles and other shrews. Carnivorous

*NOTE: The shrew is not actually a rodent. Instead, it is a member of the insectivore family along with moles. However, because many people consider them a rodent, we have thus included them.

Threats:

Saliva contains venomous neurotoxin and a bite can be painful
Emit unpleasant odors, especially noticeable indoors
Potential food contamination indoors

Habits:

Shrews are the only venomous mammals in North America
Spend most of their time underground
Solitary
Territorial
Nocturnal, sometimes diurnal
Prefer rich, moist leaf litter or thick plant cover
Active year-round

Reproduction and Lifecycle:

There is limited available information on the reproduction and lifecycle of the Northern Short-Tailed Shrew. Typically, mating begins in March and ends in September but may continue year-round. Females are known to have at least two litters of shrewlets per year with a gestation period of approximately 21 to 24 days. Typically, 6 to 8 shrewlets are born to each female and will suckle for as many as 25 days before being weaned. At 2-3 months, the weaned shrewlets become sexually mature and are able to successfully reproduce in the same year they were born.

Nests and Colonies:

Shrews are solitary and territorial mammals, able to burrow as fast as 2.5 centimeters per minute to form their nests, latrine, food storage and other tunneling. The nest of a shrew may be as large as 8 inches in diameter. These will often be lined with leaves or fur from the meadow vole. Nests are kept tidy and clean.

Preventative Measures:

Reduce or remove leaf litter
Maintain a well-kept lawn
Seal all entry areas into structures
Reduce heavy foliage around a structure

Norway Rat

Scientific Name: Rattus norvegicus
Color: Brown with scattered black hairs, gray to white underbelly
Tail: Shorter than head and body
Size: 7 to 10 inches long
Characteristics: Long with blunt muzzle and thick waist. Small eyes and ears. Bristly fur
Region: Throughout the U.S.
Food Sources: Seeds, plant matter, insects, human food. Omnivorous

Threats:

Will gnaw on virtually anything
Can cause significant property and structural damage
Known to cause structure fires by chewing wires
Carriers of serious diseases: Rat bite fever, Cowpox virus, Salmonellosis, and more.
Can introduce plague-infected fleas to an environment
Cause significant economic damage to food and foodstuffs

Habits:

Social
Nest tightly together
Prefer lower levels of a structure
Nocturnal and sometimes diurnal
Enjoy sewers
Forage primarily at dusk and dawn
Known to gnaw through lead pipes
Usually require a water source nearby
Very habitual creatures
Will travel 25-100 feet from burrows in urban areas and up to 150 or more if necessary
Love dog food, vegetables, fruit, meat, grains and many human foods
Hoard food

Reproduction and Lifecycle:

Norway rats can produce up to 6 – 12 litters each year. If conditions are favorable, reproduction can continue all year long. Once bred, the gestation lasts approximately 21- 25 days, and litters can contain as many as 14 pups. At 3-4 weeks old, pups are weaned and ready to begin life on their own. Both the male and female can begin successfully mating at only 3 months old. It has been estimated that a single pair of breeding Norway rats could be responsible for more than half a billion offspring in just 3 short years.

Nests and Colonies:

Norways typically construct underground burrows or ground-level burrows under hard surfaces. They may line the nesting area with a variety of available resources, from soft papers to plastics, string, and other fibrous materials. Although Norway rats share burrows and raise their young together, each female will have her own nesting chamber.

Often, nests may be found under concrete slabs, under wooden floors close to the ground, in crawlspaces, under plants and shrubs, and other similar areas.

Preventative Measures:

Reduce food sources
Clean up unused birdseed
Keep pet food in sealed containers and do not offer free choice feeding
Remove all pet feces from the lawn
Reduce sources of water
Eliminate wood piles
Maintain dry basements and crawlspaces
Eliminate accessible garbage
Monitor livestock feeds and barn lots
Reduce ground cover and foliage adjacent to structures

Roof Rat

Scientific Name: Rattus rattus
Color: Brown with intermixed black
Tail: Longer than head and body at 7-10 inches. Scaly
Size: 6-8 inches
Characteristics: Soft and smooth fur, Thin waist, large eyes, large ears. Pointier nose than the Norway. Underbelly is black
Region: Worldwide
Food Sources: Omnivorous. Seeds, nuts, fruits, berries, snails, slugs

Threats:

Can show aggression when threatened
Transmitters of rat-bite fever through a bite or scratch also transmit leptospirosis, salmonellosis, murine typhus, plague, and others
Carry ectoparasites such as fleas, mites, lice and ticks
Cause millions of dollars annually in food contamination and loss
May gnaw through many building materials to cause significant damage to a structure, including potential fire
Eat and contaminate stored foods

Habits:

Nocturnal
Prefer heights in buildings and tree tops
Commonly travel utility lines, tops of trees, and vines
The most common rat found in attics

Reproduction and Lifecycle:

Roof rats can produce litters of 6 to 20 (6-8 most common) pups and have a gestation period of only 20-24 days. For the first 17-23 days, roof rat pups remain in the nest. Nests are typically in high areas such as attics. Pups open their eyes at about 2 weeks and are weaned at 4 weeks. By the 12th week, the pups are on their own and ready to reproduce. Offspring usually stay close to their birthplace and rarely venture out to find new territory.

Breeding season varies in different areas but can take place year-round. Females may produce multiple litters per year and as many as 40 or more offspring.

Nests and Colonies:

Information is limited.

Prevention:

Seal holes, gaps, and cracks in structures
Trim shrubs, trees, and vines away from structures
Screen all vents and windows
Eliminate food sources
Remove unused fruits and nuts that fall from nearby trees
Keep garbage in containers that prevent rat access
Store pet and animal foods in airtight containers
Reduce unnecessary sources of water
Install door sweeps on exterior doors
Keep firewood or other stacked items away from structure
Keep attics, crawlspaces and similar spaces dry and well-ventilated

Vole

Scientific Name: 4 species found in KY
Color: Brown to brown and red
Tail: short
Size: 4 – 6 inches
Characteristics: Thick cylindrical shaped body, small, sometimes hidden ears, dense fur
Region: Throughout KY (many vole species exist throughout the world)
Food Sources: Grasses, forbs, seeds, tuber roots, insects, bulbs, legumes