Common Rodents in Southern California

Rodents are warm-blooded mammals that, like humans, can be found throughout the world. They have oversized front teeth for gnawing and check teeth, which are adapted for chewing. Rodents chew on a variety of items available to them and cause great damage in and around homes.

RATS

Rats are thin-tailed, medium-size rodents that originated in Asia and Australia but are now found all over the world. "True rats" are members of the genus Rattus, but other rodent genera are also referred to as rats and share many of the same characteristics. Rats differentiate from mice by being larger, with longer, thinner bodies and long legs.

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MICE

House mice are said to be the most common mammal in the U.S., so it’s no surprise that many homeowners report dealing with infestations at one time or another. Because mice are so common, you may think you already know all there is to know about this household pest, but think again!

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TIPS FOR CONTROL

The best way to avoid invasions of rats is to provide as little harborage as possible that might attract rodents, and seal as many holes and cracks in the outside of the home as possible through which rats might enter. The following recommendations should be followed to help prevent rats from seeking the food and shelter provided by your home:

→ Keep firewood stored as far from the home as possible and store it off the ground. During the winter, store only enough wood next to the house to burn every couple of days.

→ If possible, remove any piles of debris, stones, bricks, etc. If these are near the foundation of the home, they serve as harborages to attract rodents. Once there, it is an easy step for rodents to enter the building itself.

→ Seal any hole or crack larger than one-fourth of an inch. Large holes or cracks should be stuffed with steel wool or wire mesh before sealing with caulk or foam, otherwise rodents could chew through to enter.

→ Install a good, thick weather stripping on the bottom of all doors to prevent rodents from entering. The garage door may prove difficult to seal completely, so the door from the garage to the house must be tightly sealed.

→ Remember, our service includes coverage of commensal rats and mice, and much of the service provided during the colder months is to inspect for signs of rodents and to maintain preventative control measures.

Rats

Facts & Information

Types of Rats

Norway Rat

Rattus norvegicus

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Roof Rat

Rattus rattus

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Pack Rat

Sigmodon hispidus

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Norway

The Norway rat commonly referred to as the street or sewer rat, is believed to be of Asian origin, arriving in the U.S. on ships from other countries in the 1700s. Today, Norway rats are found throughout the world. Norway rats have fairly poor vision and are colorblind. Despite this, their other senses, including hearing, smell, touch and taste are keen. Although not extremely agile, they are capable of running, climbing, jumping and swimming. Norway rats are known to cause damage to properties and structures through their gnawing.

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Brown with scattered black hairs; gray to white underside.
Norway rats have bristly brown fur, with black hairs dispersed throughout their coat. Their underside tends to be lighter, with gray to off-white coloring and even yellow tones.

Norway rats have small eyes and ears, and their tails are shorter than the length of their head and body coupled together.
They can reach lengths of 10 to 12 inches., and their tails alone can measure 9 inches. They are large rodents that may weigh in excess of 500 grams.

Norway rats are nocturnal. They characteristically forage at dusk, and then again prior to dawn. However, they eat several times each night and during the daytime. These rats will carry the food they find to less busy areas for consumption, or to hoard. Adaptable feeders, Norway rats eat practically anything but show a preference to meat, fish and cereal. This differs from the eating habits of roof rats, which prefer fruits and vegetables. Dog food is also a favorite menu item for Norway rats.

These rodents are known to gnaw through almost anything – including plastic or lead pipes – to obtain food and water sources for survival. Norway rats almost always require a water source separate from the liquid they may find in food. They are creatures of habit. If they eat something they dislike, Norway rats will quickly develop an aversion to that food and search for an alternative option. Once they find a favorable food source, Norway rats will return time and again. They tend to follow the same route—usually along a vertical pathway that they feel out with their long whiskers—between their shelter and sources of food and water. They will typically travel about 100 to 150 feet away from their shelter for food and water, although this range is smaller in urban areas where they will venture only about 25 to 100 feet away from their home.

Norway rats can reproduce quickly, giving birth to about three to six litters each year. This makes it all the more important to take proactive measures, such as Norway rat control, to prevent an infestation from taking root.

Roof rats are highly adaptable. They are nocturnal by nature and are accomplished climbers. They prefer to live in high places, but may live in a variety of environments if necessary. Their nests can be found in:
→ Attics
→ Buildings
→ Garage storage spaces
→ Piles of rubbish or wood
→ Rafters
→ Roofs
→ Trees
→ Wall voids

When outdoors, Norway rats tend to live in fields, farmlands and structures. They frequently burrow in soil near riverbanks, in garbage and woodpiles, under concrete slabs, and along railroad embankments, streams and riverbanks. Norway rats typically enter homes in the fall when food and water sources become scarce outside. These rodents can fit through a hole the size of a quarter, easily gaining entry into homes to nest. Once inside a home, Norway rats often nest in basements, piles of debris or undisturbed materials. They also enjoy nesting on the ground floor and on the lower floors of buildings, as well as in sewers. Although they prefer settling on lower levels, Norway rats may also occasionally reside in attics, on roofs and other high points.

Disease
Norway rats can be carriers of various diseases that can transfer to humans through rat urine and feces.

Damage
These rodents often severely damage building interiors by:
→ Chewing on wiring or belongings
→ Contaminating food
→ Damaging foundations with their burrows

Thanks to their propensity to gnaw through almost anything, Norway rats can cause damage to properties and structures, making them a threat to homeowners. Equally important, Norway rats are carriers of serious diseases, including jaundice, rat-bite fever, cowpox virus, trichinosis and salmonellosis. Learn more about the health threats posed by rodents in the article, “An Overview of the Real Health Risks Posed By Mice and Rat Infestations.” Norway rats also pose other health threats, as they can contaminate food and introduce fleas into a home.

Plague is infamous for killing millions of people in Europe during the Middle Ages. It is a disease that affects humans and other mammals and is caused by the bacterium, Yersinia pestis. Humans usually get plague after being bitten by an infected rodent flea or by handling an animal infected with plague, such as a rodent. The last urban outbreak of rat-associated plague in the United States occurred in Los Angeles in 1924-1925. Presently, human plague infections continue to occur in rural and semi-rural areas in the western United States.

Roof

The roof rat is the smaller of the two commensal rats, as the Norway rat is larger in size. Roof rats are also referred to as black rats or ship rats. The roof rat gets its name from its tendency to find shelter in the upper parts of buildings. Once inside, roof rats not only damage materials by gnawing through them, but they also contaminate stored food and serve as vectors of dangerous diseases.
Roof rats are thought to be of Southeast Asian origin, but they are now found worldwide, especially in the tropical regions. Roof rats are common in coastal states, seaports and the southern third of the country.

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Brown with black intermixed; Gray, white or black underside.

Roof rats are long and thin rodents that have large eyes and ears, a pointed nose and a scaly tail. Roof rats have soft and smooth fur that is typically brown with intermixed spots of black.Their undersides are often white, gray or black.

Adult roof rats measure 6-8” (16-20 cm) when combining their head and body length. Their tails are notably longer than their heads and bodies, measuring 7-10” (19-25 cm). This means that roof rats can measure more than 40 cm long. They usually weigh 5-9 ounces (150-250 g), but can grow up to 12 ounces (340 g).

Roof rats are omnivorous and willing to eat practically anything available to them. However, they prefer to feed on seeds, nuts, fruits and berries when in season. Additionally, they will feed on slugs and snails, which may become a large part of their diet. Roof rats also feed on insects including American and brown cockroaches. If they live near bodies of water, they will eat fish, shellfish and other aquatic organisms.

Roof rats typically feed at dusk and again prior to dawn, although they will forage several times per night and during the day. Roof rats in particular are food hoarders, meaning that they have been known to stash supplies of things such as nuts and seeds. When eating, they prefer to be in a sheltered or hidden environment.

Roof rats are primarily nocturnal, and thrive in cool weather. They forage for food in small groups of up to ten and tend to return to the same food source time after time, following the same pathway between their nest and food. Though their excellent climbing abilities allow them to easily access the upper parts of structures, they are also highly adaptable and can survive in a variety of environments.

Typically living in colonies, roof rats prefer to nest in the upper parts of buildings, such as attics and rafters. They can also be found under, in and around structures, as well as in piles of wood or debris. Generally preferring sheltered or covered habitats, roof rats are attracted to lush landscapes, dense vegetation and fruit trees. As result, properties with heavy shrubbery, woodpiles and storage boxes are more prone to roof rat infestations.

When looking for indoor shelter, roof rats will enter structures through any access point larger than a nickel. Seeking safety from predators and places to nest, they enter garages, sheds and homes by following pipes or gnawing through materials such as drywall, aluminum siding, and wood.

Roof rats only live up to one year, but have the ability to produce as many as 40 new offspring during their lifetime.

Roof rats live in colonies and prefer to nest in the upper parts of buildings. They can also be found under, in and around structures.

Roof rats can cause extensive and costly damage from:
→ Chewing on electrical wires
→ Damaging furniture and storage boxes
→ Ripping up insulation

Diseases
Roof rats spread diseases like salmonellosis through pantry foods contaminated with their droppings. These rats can also transmit rat bite fever through bacteria in their mouth. Trichinosis may be contracted through eating undercooked meat of animals that have fed on rats. Rats contaminating food or food preparation surfaces can transmit food poisoning.

Roof rats are the principle reservoir of plague throughout the world. Historically, infected fleas have transmitted serious plagues from rats to humans. Bubonic plague was a scourge in Europe several times throughout history. There are still outbreaks of plague in the United States and around the world today.

Hantavirus
Hantavirus pulmonary syndrome is transferred via inhalation of:
→ Droppings
→ Rodent urine
→ Saliva

How Do They Transfer Diseases?
Common ways roof rats transmit diseases are from:
→ Bites
→ Contamination
→ Droppings
→ Fleas that feed on the rodents
→ Physical contact

Rodents such as rats and mice are associated with a number of health risks. In fact, rats and mice are known to spread more than 35 diseases. These diseases can be spread to humans directly through handling of live or dead rodents, contact with rodent feces, urine, or saliva, as well as rodent bites. Diseases carried by rodents can also be spread to humans indirectly through fleas, ticks, or mites that have fed on an infected rodent.

Pack

These rats are called pack rats because of their characteristic accumulation of food and various debris, which they keep stocked in their dens (or near their den area). Such collections may include edible plants, small pebbles, sticks, feces, insect and vertebrate remains, shiny metal objects, and other small items taken from humans.

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Varies in color from cinnamon to brown, gray, yellowish-gray, or creamy buff, depending on the species and specimen. The underside is more lightly colored than the upper part of the rat.

Medium-sized rodents whose bodies measure about eight inches, with the tail slightly shorter than the head and body combined.

Pack rats get their name from their habit of taking small, bright or shiny objects and hoarding them in their nests. They will take beer can tabs, bottle caps, bits of foil, coins and jewelry just to name a few items. Often, sticks or nuts the rat was carrying at the time are left at the site where the shiny object was acquired, thus the additional nickname of "trade" rat. They are mainly nocturnal creatures but may be active during the day. After establishing themselves within a building, pack rats will feed on foods within the building, but will continue to forage for most of their food outdoors.

Pack rats make massive multi-layer nests, which feature “middens”, central sections consisting of branches, debris, and small stones held together by pack rat urine and feces. These middens often attract cockroaches and other pests.

These rats will also rip up mattresses and furniture, to use the soft padding to line their nests, and steal and store household items, especially trash and metallic objects, such as utensils, coins, keys, and jewellery.

Life Cycle
Breeding occurs in spring. Pack rats have litters of two or three babies after a gestation period of about a month. Mothers raise newborns in nests and wean them after four weeks. A pack rat reaches maturity in about a year and has an average lifespan of around three years.

Pack rats are found throughout the United States except in a few states around the Great Lakes and the northeastern United States. These rats tend to be more of a problem in buildings in the western part of the country. Most species of pack rats are excellent climbers and some are actually semiarboreal in preference - meaning they will nest in trees. Others are ground nesters and will dig burrows in which to live. Numerous rats may occupy a single den.
Most areas, from dry deserts to mountains and plains, are host to at least one species of pack rat. In general, the pests can survive anywhere within their habitat range that provides shelter and a food source. This makes homes and yards inviting.

Like all rats, pack rats can transmit many diseases, as well as contaminating food with their faeces, saliva, and urine and the parasites like mites and ticks that they carry with them.

Pack rats give birth to much smaller litters than other rats, producing only two or three offspring at a time, so in theory an infestation should be more manageable. However, they live much longer than other rats, with an average lifespan of about three years, so can stick around.

Take measures to try to prevent pack rats entering your home, but once inside, it’s crucial to get the help of a professional pest control service, to set up traps, bait, and a sanitation program.

Mice

Facts & Information

House

The house mouse (Mus domesticus) is the most commonly encountered and economically important of the commensal rodents. House mice are of Central Asian origin, but they are distributed worldwide and can be found throughout the United States. House mice are not only a nuisance, but they can pose significant health and property threats.

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House mice are typically dusty gray with cream-colored bellies. Fur color varies from light brown to dark gray depending on the mouse’s location.

House mice have four legs and a round shaped body. Their muzzles are pointed, and their ears are large with some hair. House mice range from 2.5 to 3.75 inches long. Their tails are usually 2.75 to 4 inches long.

In nature, mice prefer to eat cereal and seeds, but they will also eat insects, nuts and fruits. Inside structures, mice will consume almost any human food, but prefer grain based products.

House mice are very social. They organize themselves in social hierarchies with one male dominating lower-ranking males and a large number of females in a given territory. Mature male mice are socially compatible with related mice, but they are hostile and aggressive towards strangers. The size of a house mouse’s territory varies, but it is frequently no larger than 4-5 feet. The size of the territory varies based on the availability of food and water. They are excellent climbers and can jump up to a foot high; however, they are colorblind and cannot see clearly beyond six inches.
House mice nibble, eating only small amounts of food at a time. They generally feed at dusk and before dawn, but they may also opt to eat smaller meals in between.

House mice live in structures, but they can survive outdoors, too. House mice prefer to nest in dark, secluded areas and often build nests out of paper products, cotton, packing materials, wall insulation and fabrics. House mice are nocturnal, but they can be spotted in the house during the day. House mice are very inquisitive and tend to curiously investigate changes in their habitats. They will often change their established runways for this reason.

House mice can pose serious health threats. House mice can carry diseases and contaminate stored food that they eat in the home. House mice have been implicated in the spread of salmonella through their feces. Humans can become ill by consuming salmonella contaminated food. Symptoms of salmonellosis include diarrhea, fever and abdominal pain. House mice may also spread rat bite fever, although this is uncommon. Humans can catch this bacteria-borne infectious disease through contact with a dead mouse or by consuming food contaminated by mouse feces. Symptoms of rat bite fever may appear between 3 and 10 days after contact with a contaminated mouse and include fever, vomiting, headache, rash and muscle pain.
Micro droplets of mouse urine can cause allergies in children. House mouse feces in the home carries bacteria. Inhaling dust that contains dried feces may cause allergies or asthma flare ups. Furthermore, mice can also bring fleas, mites, ticks and lice into your home. If you suspect that your symptoms are associated with rodent infestation, seek medical attention. Be sure to tell your doctor if you suspect contact with rodents or rodent droppings.

Each winter, mice and other rodents invade an estimated 21 millions homes in the United States. Mice typically enter our homes between October and February, looking for food, water and shelter from the cold.

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