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Rats

Rats are classified as a pest species due to their habits of living in houses, gnawing, and spreading diseases. The most common complaints include the following:

  • Rats living in an attic
  • Rats scratching inside the walls
  • Rats raiding the pantry
  • Gnawing of electrical and communication wires
  • Concerns over health risks

For these reasons, people have these rodents trapped and removed.

The first and most important thing you have to do is find out how the rats are getting inside the building. There are holes all over – missing roof vent screens, plumbing stacks, gaps between the roof and fascia board, gaps in the siding, areas where pipes go into the house, etc. etc. You will never solve a rat problem until you find all of these openings, and seal them shut with steel, which rats are unable to chew through.

Only after you’ve sealed the openings shut, you should start trapping and removal. I highly recommend snap traps, not live cage traps, certainly not glue boards, and most definitely not poison! Never poison rats, it doesn’t solve the problem and it just creates more problems..

Monitor the situation. Check the traps periodically, remove any dead trapped rats, and reset the traps. Listen for rat evidence, like their scurrying and running noises in the attic, and scratching in the walls. Look for fresh droppings. Check the repairs done, to  make sure no new areas have been chewed open. If you’ve sealed the house correctly, then you shouldn’t trap any new rats after just the first three days.

Once you’re satisfied that there is no more evidence of rats, and you are not trapping any new rats, you should clean the attic or whatever area they were living in, to remove the contamination and biohazard, and also to eliminate the rat scent, which will attract new rats to try to chew their way into the house in the future.

NUISANCE CONCERNS: Rats and mice may be the most commonly known nuisance mammal species worldwide. They can be important agricultural pests, but the real concern is their tendency to feed on human food stores, often contaminating what they do not eat. They also chew, and can destroy electrical wires and pretty much anything they get their teeth on. The wire chewing can cause electrical shorts, or worse, fire risks. Sometimes they chew on PVC plumbing and cause water leaks.  Most of the calls that I get regarding rats has to do with the noise people hear the rats making up in the attic or in the walls. They leave behind a lot of waste in the form of urine and feces. They’re also known carriers of zoonotic diseases of course.

RAT BIOLOGY:


Roof Rat (Rattus rattus) Is also known as the Black Rat, Ship Rat, or House Rat. It is very common in the more southern states. Adults average 7-8 inches long with an additional 8 inch tail, and weigh between 6-10 ounces. Males are usually larger. They breed year-round, and have up to five litters per year. A female can become pregnant within 48 hours after giving birth. The young grow quickly, and are sexually mature within three months. It’s rare for rats to live more than one year in the wild, though lab/pet rats can live up the three years. They love to live in attics, hence their name.
Common Name: Rodent – Roof Rat
Latin Name: Rattus rattus
Common Family Name: Rats and Mice
Latin Family Name: MuridaeOther Names: Black rat, ship rat, house rat, tree rat, climbing rat, white-bellied rat. Also as two subspecies called the fruit rat (Rattus rattus frugivorous) and the Alexandrine Rat (R. r. alexandrinus).

Origin: Native to forested areas in Southeast Asia, but transported into Europe by caravans as early as the 11th century. It was the common structural rat in Europe during the Black Death episode in the 14th Century. It arrived in the United States somewhere in the 1500’s, although this is not certain. In the U.S. it is not as widespread as the Norway Rat, generally staying within 100 miles of a coastline, and occurring throughout cities from Washington to southern California, along the Gulf Coast and up the entire eastern seaboard.

Biology: The Roof Rat is an “arboreal” animal, preferring to live above ground level in trees, although it has adapted well to upper areas of structures as well, living in attics and traveling by means of wires and cables attached to homes. It is nocturnal and secretive, staying out of view within the foliage provided in landscaped environments, and feeding heavily on the fruits, nuts, vegetables, or garden snails found there. Like the Norway Rat is also is shy about new objects in its familiar environment, and may avoid control measures such as traps or bait stations. A normal life expectancy for them is one year or less, ranging from 5 to 18 months. The gestation period of the female is 22 days, litters average 8 to 9 pups, and she may have 3 to 4 litters in her one year, being somewhat less prolific than the Norway Rat. Peaks in breeding occur in the spring and the fall. Problems from Roof Rats include the potential for disease, such as plague, spread by their fleas. They are extremely destructive to stored food products in structures, crops in residential areas, and cause tremendous damage due to their gnawing on structural members, pipes, and electrical wires.

Identification: The Roof Rat is a smaller, slimmer rat than the Norway Rat, and cannot compete with the Norway when space is limited. Its tail is noticeably longer than its body length, the best ID characteristic in the field. In relation to its head it has a pointed nose, large eyes, and large ears. Its color is dark gray to black with a lighter grayish belly, and it ranges to a lighter brown depending on which “subspecies” is present.

Characteristics Important in Control: Exclusion from structures is of high importance in preventing entry and damage from this rat. They can enter through any opening wider than one half inch, swim well, and can climb any rough surface, along wires and cables, and can jump vertically about 3 feet. Glue trays work very well for Roof Rats, along with snap traps placed in runways and bait stations using various formulations. Like the other domestic rodents they prefer to remain against vertical surfaces, in contact with their “guard hairs” on their body, and control measures should be placed against these pathways.

Norway Rat (Rattus norvegicus) Is also known as the Brown Rat. These rats are larger than Roof Rats, with a more robust body, slightly longer, but a bit shorter tail. They can weigh up to a pound. They are more common in northern parts of the country. They are more likely to live at ground level, like below a house, or in the basement, but can inhabit any part of a building.Both types of rats have excellent hearing and sense of smell, but poor eyesight. They often travel via urine or pheromone pathways. They have excellent speed and balance, and can easily climb most surfaces. They seek out shelter in safe places, and they also seek out warmth and food, and that’s why you’ll often find rats in buildings.

Common Name: Rodent – Norway Rat
Latin Name: Rattus norvegicus
Common Family Name: Rats and Mice
Latin Family Name: Muridae

Other Names: Brown rat, ship rat, wharf rat, sewer rat, gray rat, barn rat, burrowing rat, water rat, common rat, house rat, migratory rat, wander-rat

Origin: Evolved in Central Asia, but reached Europe in the 1700’s, the United States later that century, and now it is found throughout the world. It is a rodent of cooler climates, but now also infests many tropical environments as well, primarily in the seaport areas.

Biology: This rat is commonly sold as a “pet rat”, and has been bred for white coloration as “lab rats” as well, leading to the occurrence of white and brown marked races. It is primarily a ground dweller, although it can climb very well, and prefers to reside in burrows. It swims very well and often lives in sewers and other underground water systems. It is primarily a nocturnal animal, and will restrict its range of movement only to that which is needed to find food and water, perhaps only 20 or 30 from home. Norway Rats are omnivores and opportunistic feeders, feeding on any natural or human foods available. They are neophobic and may avoid new objects placed in their environment for some time. A normal life expectancy for them is one year or less, although when cared for they may live several years. The gestation period of the female is 22 days, litters average 8 to 9 pups, and she may have several litters in her one year. Damage from gnawing can be extensive, as they chew on pipes of plastic or metal, wires, wood, or furnishings and walls, and commonly bite humans. While not the primary reservoir of bubonic plague, they have the potential to spread this disease, along with several others as well as filth infections.

Identification: Adult rats are large and robust, being up to 16 inches from nose to tip of tail. Their tail length is shorter than their body length, and it is scaly and almost without hairs. Colors range from white to brown to mottled, or blackish gray, reddish brown, and other variations. In relation to its head it has a blunt nose, small eyes, and small ears.

Characteristics Important in Control: Habitat modification to eliminate harborage sites is effective, along with proper building maintenance to exclude their entry. Elimination of available interior and exterior food and water supplies is needed. Burrows may be treated by fumigation in some circumstances, and the use of traps and baiting are highly effective. The shyness these rats exhibit toward new objects can affect the response to bait boxes and traps. Glue trays may not be highly effective due to the strength of this species, and its ability to pull free from the glue. Like the other domestic rodents they prefer to remain against vertical surfaces, in contact with their “guard hairs” on their body, and control measures should be placed against these pathways.


MICE AND RAT BEHAVIOR: Though than can live in a variety of natural habitats. Roof rats tend to live up in trees, whereas Norway Rats and mice live at ground level or even in underground burrows. However, these rodents are known for their association with and dependence on humans. They very frequently live in people’s homes or other buildings, especially if these buildings contain or are near food sources. These rodents establish a relatively small home range, and don’t travel very far. They are nocturnal, and wait until night, when everything is safe and quiet, before venturing out in search of food. They eat a variety of foods, but often prefer grains. They have rodent teeth that continually grow, and they gnaw on objects in order to wear down the teeth. They can be somewhat territorial, though high population densities can mess up territories.

MICE AND RAT DISEASES: Everyone knows about the now-rare Bubonic plague, or “Black Death” of the Middle Ages, but there are over 30 different types of disease are associated with rats and their droppings. They include Rat-bite fever (Streptobacillus moniliformis bacteria), which is transferred from the bite of a rat, the Rickettsia virus, which is similar to chicken pox, Hantavirus, which can cause febrile illness in humans and sometimes kidney, blood, or respiratory ailments, Eosinophilic Meningitis – an infection of the brain, and caused by rat lung worm. The droppings of rats can cause Leptospirosis or Salmonellosis, and rats and mice also bring parasites into the home.


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