The most common rat in Minnesota is the Norway rat; also known as the sewer or brown rat. Although considered to be relatively intelligent, with many interesting abilities, rats pose a serious threat to human health and can cause considerable damage to property and your reputation.
HOW DO I KNOW IF I HAVE RATS?
- Rats are primarily nocturnal (active at night), so they are rarely seen. More often, it is their tell-tale signs that indicate a rat infestation, including:
- Rat droppings – shiny black, blunt at both ends; and ½” - ¾” in length – similar in size and shape to a grain of rice. (Mice droppings are smaller and have pointed ends)
- Rat tracks – foot prints and tail tracks in dusty corners and along baseboards.
- Gnawed wood – Rat teeth leave marks approximately 1/8” in length, which are typically larger than marks left by mice.
- Rub marks – rats often leave smudges of grease and dirt along baseboards, rafters, tight passageways, and on pipes and corners.
- Rat holes – Norway rats are known to dig extensive burrow systems. Rat holes are the entrances to rat burrows and are often found next to structures.
- Rat nests --rats will make nests in burrows, attics, and even wall cavities by shredding soft materials such as cloth, cardboard, and insulation.
- Rat odor – a rat or mouse infestation often creates a musky odor.
- Rat noises – scratching, squeaks, gnawing, clawing, and other unusual sounds you hear during the night might be rats.
WHERE TO LOOK?
- Norway rats tend to inhabit the lower levels of buildings.
- Look for rat droppings in corners, in cardboard boxes, behind appliances like stoves, refrigerators, washers and dryers.
- Although Norway rats inhabit crawl space and basement, they might also take a shelter in an attic. Look for rats’ nests in attic spaces, behind clutter and infrequently used storage areas, in crawlspaces, suspended ceilings, near food and water sources, and wall cavities.
- Smudge marks (rub marks) can be found anywhere along a rat’s frequently traveled route. Check any gaps where pipework or cables enter your property from outside and along baseboards and behind appliances.
- Look for rat holes around the base of sheds, garages, crawl space and other outbuildings.
- Gnaw marks can be found on the edges of decks, door frames, the bottom of wooden doors, around pipes and any vents through exterior walls. Entry holes are typically 2” or larger for rats. (Mice can enter through a hole or gap as small as the diameter of a pencil.)
- Rat runways can be found next to building walls, under debris. Rats are intelligent and will memorize and habitually use the same route.
WHAT DO RATS LOOK LIKE?
- Rats are generally larger than mice. Rats have disproportionately long feet and oversized heads when compared to mice. A rat’s nose is round, while mice have a triangular shaped nose.
- Norway rats are larger than most other rat species.
- Norway Rats are 13”- 18” in length including a 6” - 8 ½“ tail
- Weigh approximately ¾ pound (12 ounces)
- An adult Norway rat is typically dark grey-brown with occasional black hairs.
- The ears and tail are hairless.
- Norway rat tails are shorter than their body length
- Their ears and eyes look relatively small to their body size.
ARE RATS DANGEROUS?
- Yes, rat infestations can be harmful to human health. Rat droppings and rat urine can transmit diseases, including: Salmonellosis (food poisoning), Leptospirosis (which can result in liver and kidney damage), and Lymphocytic choriomeningitis (LCMV).
- Rat bites and scratches can result in disease and rat-bite fever.
- Rat droppings, dander and hair can also cause allergic reactions in people.
- Although no longer considered a wide-spread threat, the bubonic plague, also called “Black Plague,” killed millions of people during the Middle Ages. It is thought that fleas from roof rats (Rattus rattus) transferred the plague by biting human beings
CAN MY PROPERTY BE DAMAGED BY RATS?
- Yes. Rats can damage your property by gnawing on wires, insulation, doors, window sills, walls, ceilings, floors, and drywall.
- Rats can also damage furniture, carpet, storage boxes, and personal items by gnawing and by defecation.
- Rats can undermine the structural integrity of buildings by burrowing under foundations and slabs; causing settling of slabs and damage to landscape berms.
- Norway rats consume and contaminate foodstuffs and can contaminate food prep areas and food packaging materials.
- Rats are known to damage field crops prior to harvest, and during processing and storage.
WHY ARE RATS TO MY PROPERTY?
- Generally, rats are attracted by food and shelter.
- Garbage left outside in a container without a tight, shut lid, bird seed spilled on the ground or stored in a paper bag, pet food outside or in a garage or shed, even fruit left fallen on the ground will attract rats.
- Any food source that isn’t stored in a plastic container with a lid, can attract rats.
- Debris and clutter will attract rats looking for shelter.
- Norway rats are known to enter a structure through sewer lines, especially in winter.
WHAT DO RATS EAT?
- Norway rats are scavengers and will eat a wide variety of foods, including grains, meats, fish, nuts, and some fruits.
- Norway rats prefer high protein foods such as pet food or meat scraps.
Rats must drink water nearly everyday
WHAT IS THE LIFECYCLE OF A RAT?
- Norway Rats reproduce quickly.
- While rats can breed any month of the year, breeding is most active in the spring and autumn.
- In a large rat population, several males will mate with a female sequentially, in the order of their social dominance.
- A female Norway rat can have as many as 12 litters per year; although they average 4-6 litters per year.
- Litters may number from four to 22 young; however litters of 6-12 are more typical.
- Litters are born 21 to 23 days after mating.
- Rats are born hairless with their eyes closed.
- Rats can eat solid food at 2 ½ - 3 weeks.
- Norway rat reaches reproductive maturity in 2-5 months.
- Rats can live up to 18 months, but most generally live up to one year.
20 INTERESTING FACTS ABOUT RATS:
- Rats are considered to be intelligent, creative, and have an excellent memory.
- Rats’ ability to demonstrate intelligence, sensing, and memory is comparable to dogs and elephants.
- Rats will memorize pathways, obstacles, the location of food, water, and shelter; which is what makes them ideal laboratory animals for studying learning and psychology.
- Rats can quickly identify new objects placed into their environment and will tend to avoid them.
- Rats have an excellent sense of taste and can identify certain substances, including rat poison, after just a tiny taste of it.
- Rats will make a happy sound that is similar to laughter when they are happy or playing.
- Rats’ ability to climb and scamper along narrow ledges is due in large part to their tails, which give rats an exceptional sense of balance.
- Rats can swim continuously for up to three days.
- Rats can fall from a height as great as 50 feet and land uninjured.
- Rats do not sweat. Their temperature is regulated by constricting or expanding blood vessels in their tails – which is why their tails don’t have fur.
- Rats' front teeth grow 4½ to 5½ inches each year. Rats wear them down by continuously gnawing on everything around them, including cement, brick, wood, and lead pipes.
- While they are vectors of several diseases, it is extremely rare for a human to get rabies from a rat.
- Rats can sense and respond to tension in humans.
- It is believed Norway rats arrived on ships from Great Britain around the time of the American Revolution.
- The number of rats in the US is estimated to be roughly the same as the number of people.
- Minneapolis-St. Paul ranked 8th in Orkin’s 2016 list of rattiest cities; behind perennial Chicago (1) and expected New York City (2) and Washington DC (3); but ahead of Detroit(9), Boston (12) and New Orleans (38).
- More than 20,000 rats are kept in a Hindu temple in Deshnoke, India. Many people make a pilgrimage to the temple to pay respect to the rats, which are believed to be reincarnations of Karni Mata and her clansmen.
- A popular sport in 19th-century London was “rat baiting,” which involved betting on how long it would take a man or a dog to kill a number of rats in an enclosed area. The record was set in 1862 by Jacko, a 13-pound bull terrier, when he killed 100 rats in 5 minutes, 28 seconds.
- In Chinese astrology, the rat is the first in the zodiac cycle and happens every 12 years: 1912, 1924, 1936, 1948, 1960, 1972, 1984, or 1996, 2008, 2020. People born in these years are characterized as having spirit, wit, resourcefulness, and flexibility.
- Rats can hear and produce ultrasonic sounds that we cannot hear.