Recent years have brought a new surge of rat infestations in some major American cities. In 2016, USA Today reported increases in unwelcome rat populations in New York, Chicago, Boston and Washington, DC, with the biggest increase noted in Chicago, with an increase in the rat population in the range of 70% year over year. That same year, New York received more than 41,000 complaints of rodent activity. And in Baltimore, residents in low-income areas where rats were prevalent were found to have higher rates of depression than residents of other parts of the city.

With statistics like these in mind, cities are bolstering the resources they’re deploying against rat infestations. Chicago is increasing the number of city-employed rodent technicians and experimenting with new ideas to help the Chicago Transit Authority reduce rats in public areas.

Boston has started a 311 line specifically for reporting rats. The city has also worked with MIT and Harvard to test an approach using dry ice that seems, at least from initial reports, to be working.

Cities are also cracking down on residents who contribute to the problem. Chicago fines homeowners up to $500 for leaving pet droppings or garbage in their yards, with other cities following suit. Some homeowners are unhappy about these efforts, but many are taking matters into their own hands rather than waiting on the city.

The Risk of Disease

Every interaction with rats should be taken seriously. Rats do not have to bite in order to cause illness; exposure to rat waste is the cause of many debilitating diseases. Rat urine is one of the leading causes of leptospirosis, a condition can cause severe  kidney and liver damage among humans.

Other diseases that are specifically carried by rats include, but are not limited to:

  • Salmonellosis – a disease that can cause abdominal cramps, diarrhea, intense vomiting and fever. Symptoms can begin as soon as 12 hours after exposure.
  • Weil’s disease – a severe form of leptospirosis, caused by the same bacteria. If leptospirosis reaches this stage, you will likely have to be hospitalized. Severe reactions may occur in the lungs, the heart, and the brain, if the bacteria reaches those organs.
  • Rat bite fever – a disease which can be passed to humans from rat urine or mucus. It is also known as epidemic arthritic erythema, streptobacillosis, streptobacillary fever, sodoku, and spirillary fever. Symptoms may include chills, fever and intense vomiting.
  • The plague – which can be spread through airborne contact in extremely unsanitary areas. The bubonic plague, one of the longest- lasting rodent-borne diseases in the world, is only one manifestation of this disease.
  • Hantavirus – a disease serious enough to require a report to the Centers for Disease Control and Prevention (CDC) if contracted. If it progresses to Hantavirus Pulmonary Syndrome, it can be fatal.

How to Tell Rats from Mice and Other Rodents

There is no official scientific difference between a rat and a mouse. In fact, many rodents identified as rats in a visual sense are actually not closely related at all. Many rodents that are referred to as rats include pack rats, naked mole rats, wood rats, cotton rats, Norway rats, and kangaroo rats. However, species that are identified differently, such as Norway rats and house mice, are both descended from a single ancestor.

Scientifically, rats are usually defined as rodents with more pairs of chromosomes than mice (22 to 20). Rats also generally develop more slowly than mice, with a gestation period of 24 days rather than 19 days. Most rats will also have more nipples than mice.

The general consensus in defining a rat agrees on one thing: size. If a rodent seems large in comparison to other similar looking rodents in its geographical area, it is considered a rat. Rats also generally have larger feet and ears, with large, chunky heads.

Identifying Types of Rats

The industry for rats as pets has done a great deal to help people classify the different types of wild rats that infest major metropolitan areas. Although the distinctions are not scientific, the descriptions may help you determine the type of rat that you see around your property.

The rat body type corresponds to 4 different distinctions.

  • Standard – This is the most common body type and usually corresponds to wild looking, large ears on a rodent.
  • Dumbo – The ears on a dumbo rat are larger than the Standard type, and they are also set much lower on the head.
  • Manx – Compared to the Standard body type, the Manx has a slimmer and smaller body overall.
  • Dwarf – Considerably smaller than other rats, these are distinct from mice because of their longer tails and more pointed heads.

Rats also have different types of coats in terms of their fur.

  • Standard – This is the most common type of coat and looks typical, with straight fur.
  • Rex – This coat has curly hair.
  • Double Rex – A rat with a Double Rex coat type will also have curly whiskers alongside patchy hair.
  • Hairless – This recessive trait is self-explanatory.

There are two basic colors for the color of the coat – agouti and black. Agouti is the dominant trait and usually corresponds to most wild rats. There are many modifiers that play off of this base coat, affecting the color that you see.

  • Red eyed dilute – A rat with red eyes will turn an agouti coat a fawn color and a black coat tan.
  • Pink eyed dilute – A rat with pink eyes will turn an agouti coat amber and a black coat mocha brown.
  • Albino modifier – The rat will have pink eyes and a totally white coat regardless of the color of the base coat.
  • Blue modifier – The rat’s coat will be silver or blue with tan tipped hairs if the base coat is agouti. A base black coat will come out all blue.
  • Mink modifier – This will turn an agouti base reddish brown and a black coat gray.
  • Pearl modifier – This will turn an agouti coat gold and silver and a black coat pearl.

The last modifier is a pattern modifier.

  • Self – This is the most common modifier and does not change the look of the rat.
  • Berkshire – This modifier gives the rat white feet and a white belly.
  • Blazed – Blaze leaves a “blaze” on the face between the nose and eyes.
  • Capped – The rat will only have color on its head area, with the rest of the body colored white.
  • Hooded – The hood modifier gives a rat color on its shoulders and down the back as well as on its head.
  • Irish – This type of rat is colored solid except for white paws and a single spot on the belly.
  • Masked – This is a white colored rat with color only over the eyes.
  • Roan – This rat type is born with a solid color that will fade as the rat gets older.

Inspecting Your House for Evidence of Rats

Rats leave distinctive signs of their presence, although you may never see one in your house. Here are some of the signs that you should look for if you think that you have a rat infestation.

  • Droppings. One of the most obvious signs of rat infestations, these are usually dark brown and will resemble a rice grain in shape.
  • Unusual smudges along your walls. Rats will leave discolorations on the lower parts of walls as they rub against them. The color comes from the grease and dirt they drag in from outside.
  • Scratching noises. If you hear scratching noises at night in your loft, you may have a black rat infestation. This particular species is very adept at crawling upwards.
  • Rat holes. Brown rats have the ability to dig sophisticated burrows in order to nest, store food, and shelter themselves.
  • Rat nests. If rats get into your attic or loft spaces, they may shred your insulation in order to make a nest.
  • Footprints. You may find rat-sized foot marks in the less traveled areas of your home.


Rats usually find their way into places that provide feeding opportunities. The smell from your garbage may attract them, as will the odor from old food in your cupboard or even your refrigerator. Make sure that you always immediately throw out any food that is past its expiration date.

You may also sanitize your home by regularly vacuuming and dusting. Many of the odors that draw rats are in old dust and food droppings that find their ways into the corners of your home. Make sure that you move your furniture and get in the corners of your home to clean up all of the old food and sticky dust that may attract them.

You can also sanitize your home by only eating in specified areas. If your family frequently eats in bedrooms, food will inevitably fall behind headboards and under beds, attracting rats.

You also need to protect your home from your neighbors’ sanitation problems. If your neighbors are messy or smelly, you may want to have a talk with them. You can also protect your home by setting up a rat poison barrier around your own property.

Rat-Proofing Your House

  • Start by inspecting the foundation of your home. Look for gaps or holes that may be large enough for a rat to enter. You can block off those entry points with foam or mesh.
  • Once those areas are secured, check your doors and windows. This is especially important at the change of seasons, when doors and windows may warp and leave gaps that rodents can crawl into. Metal kick plates are a good solution for these, as well as insulation treatment.
  • Next, inspect your roof. Your vents, shingles and chimneys may showcase some wear if rats are involved. Cap the chimney when it is not being used.
  • Consider using a metal rodent guard if you have any wire lines or pipelines that come from the outside into the house.

Treatment & Eradication

There are many different types of rat traps that you can buy or build. Regardless of the type you use, there are some rules you should follow for best results.

  • Use a large number of traps.
  • Make sure that you are using rat traps. Mouse traps are too small to trap rats.
  • Place the traps in the most infested areas – dark corners, behind big appliances and wherever you see droppings. You can also put them on tree limbs that overlap the house.

If you do not want to use specialized rat poison, you can use peanut butter, bacon, dog food, cornmeal, chicken feed, and even cheese with a strong smell.

When to Call a Professional

Call a professional if your own efforts do not solve the problem. Test weekly, and pay attention to the advice of your professional if he tells you that you have a worse problem than you think, because you probably do.