Get rid of rats and keep them from coming back

Roof Rats vs Norway Rats: What Are the Differences?

There is a well-known urban myth which states that if you live in a large city, you will never be more than six feet away from a rat. Despite many large rat populations across the country, you will be pleased to know that the figure of six feet is somewhat exaggerated. It’s more likely to average between fifteen feet and one hundred and fifty feet, depending on the city or type of area you live in.

Even at one hundred and fifty feet, it does not diminish the number of problems which rats can cause us, especially in relation to our health, but, before you go running off to the hardware store to buy traps or poisons, it would serve you well to understand a little bit more about your adversaries.  Let’s look at the two main types of rats that you are likely to encounter (Roof and Norway) and what are the differences between them. There is a third type of rat, the Woodrat, that you might find in the southwest but it is rarely a problem for humans.

Let’s take a deep dive into roof rat vs Norway rat, their difference, and how they affect our daily lives.

Roof Rat vs Norway Rats

Roof Rats (Rattus rattus), are most likely to be found nesting in attics and other high up places, such as ceilings, tall cabinets, and the inside of walls. Unlike many species of rats, they are excellent climbers and build their nests indoors, where the heat rises and keeps them warm.

Where there are no buildings around for them to set up their home they’ll happily nest in trees, woodpiles, and even shrubs. This harks back to their ancestor’s origins in the forests of South East Asia, where there was a multitude of vines and high ledges for them to climb, or crawl along.

The Norway Rat (Rattus norvegicus) has different origins, and despite its name, it might surprise you that it is not Norway. In fact, they originated in Central Asia, and in particular, China.

The name ‘Norway Rat’ came from an 18th-century naturalist, called John Berkenhout, who wrongly believed the rats had migrated to Western European countries on Norwegian ships. He gave it the Latin name of Rattus Norvegicus, although the fact this species of rat did not even exist in Norway, seems to confirm that their name is a misnomer.

The Norway Rat has other names such as a brown rat, wharf rat, and sewer rat and these names should alert you to the fact that Norway Rats prefer to live in underground tunnels, and cellars. They can also be found living in burrows near docks, warehouses, and garbage dumps. One thing a lot of these places have in common is there is likely to be a good supply of waste food for them to eat.

Regions where you will find Roof and Norway Rats

Where you live in the USA is going to determine whether you are most likely to see a Roof Rat or a Norway Rat. You will recall that Roof Rats prefer warmer climates, so they tend to be found living in coastal regions, running all the way from Texas in the south, along Florida, and all the way up as far north as Virginia. They also love the warmer climes of the west coast too, so California, Oregon, and Washington State can be called home to the Roof Rat population.

Norway Rats are city dwellers, so anywhere there is an urban conurbation is likely to be home to them. Obviously bigger cities such as New York, Dallas, Chicago, and Boston, will have more than their fair share of Norway Rats, but in truth, anywhere there are people, there will be Norway Rats.

If you spot either a Roof Rat or a Norway Rat, you should be able to tell which is which, relatively easily. The Roof Rat is the smaller of the two and it is often mistaken for a mouse due to their large ears and pointed noses. A Roof Rat will be colored brown or black, and if you have ever had the opportunity to view one up close, or even hold it, you would see and feel that the fur is very soft and smooth. Its underbody tends to be gray, white, or black, and its tail is longer in length than the rest of its body.

Physical Descriptions

Norway Rats have a long, thick and rounded body, shorter blunt nose and their tail is shorter than the length of their body. Their fur tends to be colored brown with some black scattered throughout, and to the touch, their fur is coarser than that of a Roof Rat.


Of course, you do not need to physically see a rat, to know that you have an infestation of them. The tell-tale sign of rat droppings is one we all dread, but on the flip side, their droppings can help us identify which species of rat we are dealing with.

Norway Rat droppings are surprisingly large and can measure, as much as 3/4 of an inch long. They are black in color, shaped like capsules, and have ends that are blunt or rounded. Given that a Norway Rat can expel over fifty droppings in a single day, they are not going to be too difficult to spot.

Roof Rats’ droppings are smaller and are unlikely to be any longer than 1/2 an inch long. Apart from the smaller sizes, Roof Rat droppings differ from those of Norway Rats, in that the ends are pointed rather than being blunt.

Even if no droppings are visible, or there has been no actual sighting of rats, there can be other indicators that you have an infestation of them.

For Roof Rats, as we know love to climb in buildings, so one clue is that they will leave chew marks. These can occur on pipework, plastic, wood, or even on wall insulation. Roof Rats can be very destructive, and it is common for their presence to become known due to them chewing through wiring and causing a power failure, or worse an electrical fire.

Norway Rats love to chew too, and their materials of choice are plentiful. They’ll gnaw at wooden crates or boxes, floor joists, and wall studs or if they fancy chewing plastic, they’ll be attracted to pipes, wire insulation, and even window sills. Metal, plaster, and even stone are not safe from Norway Rats as they will chew through just about anything that lies in the path to a source of food.

Another sign that rats have infested your property can be the sounds of them moving around behind walls, in the attic, or underneath the floorboards. Remember that rats are nocturnal creatures, so the sounds are more than likely to be heard at night.

On the point about them being nocturnal, is that seeing rats during the day is a clear sign that you have a large infestation. Normally they sleep during the day, but if their colony becomes large and food is in short supply, they will give up their sleep to go hunt for food.

A rather unpleasant indicator might be an increasingly unpleasant smell. This will be the result of a rat (or rats) dying somewhere in your property and starting to decompose. It is not nice, but it could alert you to the problem.

Don’t underestimate the ability of your pets to know when there are other creatures invading their home. Dogs and cats will often sniff, investigate, scratch at floors, or even make excited noises, when rats are in the house.

Breeding Cycles

Understanding just how quickly a colony of rats can multiply will be helped if you are aware of rats’ breeding cycles. A female Roof Rat can give birth to as many as twenty-four baby rats in a year, albeit not all at once. She becomes sexually mature after only a couple of months and can then give birth to between four and six litters a year. Each of these litters can be between five and eight baby rats.

Bear in mind that each of those newborn rats will be able to mate and give birth themselves in as little as eight weeks from their birth. From this fact is it easy to see that one single female rat can be responsible for the creation of a colony of hundreds or even thousands of rats, as each generation matures, mates, and gives birth throughout the year.

For Norway Rats, the numbers are even greater due to their litters being as many as twelve babies, each time they mate. Between mating and giving birth, the time is a little as twenty-two days, so again it is entirely possible for a very large colony of Norway Rats to be created in mere months.

There is one aspect of the breeding patterns of Norway Rats that may limit the pace at which a colony will grow. Although they potentially could breed all year round, the level of reproduction tends to slow down during hot summers and cold winters, with the peaks being in the spring and the fall. Nevertheless, even with a slow-down, there is the potential for very large colonies to be created.

The one thing to be thankful for is that both Norway Rats and Roof Rats have a relatively short lifespan of around one year. Just imagine how difficult it would be to deal with them if they lived longer and were able to continue breeding for many years.

Colony Sizes

Colony sizes for Roof Rats and Norway Rats can be influenced by many factors, and therefore being able to give a definitive number for any given colony is almost impossible. There have been some scientific studies, whereby the rat colony was given a specifically measured and an increasing amount of food each day. Based on the amount of food an average rat should eat, a calculation could then be done to give a reasoned estimate as to the increased population in relation to food consumption.

Access to food sources is the most obvious factor, but there are many others that impact positively or negatively on a rat colony’s size. Just like other mammals, rats need to drink water, so if a Roof Rat has access to yard ponds or leaky pipes, for example, they will thrive. Likewise, a Norway Rat must drink water regularly so it will seek out dripping pipes and even rain puddles.

Suitable habitation is another very important factor in the life of rats, and although there are big differences in the type of habitation they prefer, both Roof Rat and Norway Rat colonies can only thrive if they have a habitat that suits them.

As we discussed earlier, Roof Rats prefer warm indoor nesting areas, although they will also live outdoors if the conditions suit. Norway Rat colonies will be found in burrows and outdoor tunnels to name but two, and if they can access food sources and water, the colony will continue to grow.

Norway Rats tend to have small individual burrows that are either used by a single rat or a small family of rats. As the population of this colony grows, as it inevitably will through breeding, the network of burrows increases in size. As time goes on, the network becomes more and more complex, with one main opening which acts as an exit or an entrance. The rats will also create a small number of escape holes should a predator come calling.

Inevitably the size of the colony will outgrow the network of burrows and outgrow the amount of available food. At this point, Norway Rats become very territorial and will fight other rats to defend both their home and their access to food sources. This is also a time when you might see rats during the day, as weaker members of the colony forage for food while stronger rats sleep.

Roof Rats have less of a problem as colonies grow, as their nests have the entirety of all the space that is available to them in the upper parts of a building, such as an attic. Remember that given the right conditions they can also nest in trees so a lack of options in trying to find a space to call their home should not be an issue for a Roof Rat.

Health Risks

Both Roof Rats and Norway Rats are considered vermin for good reasons. In addition to the damage to your property, if you have an infestation there are several health risks to you and your family that the rats can create.

Norway Rats carry many transmittable diseases, many of which are extremely serious. The way in which they pass the diseases can vary also.

As the rats’ bodily waste such as saliva, urine, and feces build up in your home, they can generate several airborne viruses that are inhaled. These include the onset of asthma attacks, leptospirosis which can inflict serious kidney or liver damage, and salmonella which can bring on fever, abdominal pain, and diarrhea.

Norway Rats can also spread disease via physical contacts, such as biting or scratching when they are cornered. One such disease is rat-bite fever which can lead to a multitude of symptoms which include fever, skin ulcers, swelling of lymph nodes, and vomiting.

Roof Rats are no less dangerous and they too can also pass on rat-bite fever if they bite or scratch you. Another danger they pose is being part of a vicious chain, where they themselves are bitten by a flea, which then bites a human, and transmits diseases that the rat was carrying such as tularemia. Tularemia creates a fever, chills, exhaustion, and skin ulcers where the bite is located.

Of course, the best way to prevent any of this happening is to try to stop Roof Rats or Norway Rats from ever setting up home in and around your property in the first place.

Preventing Rats from gaining access to your home

In the case of Roof Rats, you want to make it as difficult as possible for them to climb and gain access to the upper part of your home. This can be achieved by sealing any cracks or holes, in both wooden and concrete parts of your home. You should also trim tree branches and shrubbery so that they are as far away from the edge of your home as possible, especially those that overhang the roof.

Naturally, Roof Rats are attracted to sources of food, so always make sure all your food garbage is properly disposed of in tightly sealed trash cans or bins. If you have fruit trees adjacent to or on your property, it is always a good idea to clear away any fruit that may have fallen on the ground so that this temptation for the rat does not attract them.

Norway Rats are attracted by similar things such as food, water, and shelter, so anything you can do to eliminate these being a source of temptation to them is to be welcomed.

Apart from the previous point about sealing all food waste tightly, you should also make sure other food sources such as birdseed or food for your cat or dog is not left outside. To take this a stage further (literally), Norway Rats will even eat pet feces, so always clean up after your pets if they do their toilet business in your garden.

Ensuring there are no easy sources of water can help reduce the appeal of your property to Norway Rats, so fixing leaky pipes or outside faucets, and turning off lawn sprinklers properly, is advised.

Sealing cracks and holes in your property is also a good deterrent in terms of not making it easy for rats to gain access. If the rats decide they’d rather set up home in your garden instead, one way to deter them is to clear away woodpiles, and other piles of debris that a Norway Rat will see as an ideal abode. Ground drains and pipes should have tight-fitting mesh or grates over their openings to block off another point of entry.

If, despite all your best efforts, you do get an infestation of rats, then the next step is to seek out a way to get rid of them, and for this task, there are a multitude of ways it can be achieved. The first thing to decide upon is whether you are going to undertake the task yourself or hand it over to a professional pest control service. This choice will often depend on how large the infestation has become, and/or how much you relish taking on the job of getting rid of your rat problem.

Whether you are going after the rats or calling in professionals, there will be two methodologies that could be used. The first is ‘trapping’ and the second is ‘baiting’. Each of these can be used in isolation, or in conjunction with the other.

Rat traps can come in all shapes and sizes, but the three main types are snap, electronic, and glue. Snap traps are the traditional spring-loaded traps, that most of us will recognize. They are quick and effective especially if they are placed in the correct locations. Electronic rat traps utilize ultrasonic waves to attract the rats, although you should normally bait them with food too. Powered by batteries, they can generate an electric shock that is strong enough to kill the rat.

Glue traps work by using a very sticky substance that literally stops the rat in its tracks. One point to note is that glue traps should never be used if you have any pets, for obvious reasons.

Baiting is the practice of positioning food in locations around your property that are laced with rat poison. It can also be used in conjunction with traps, especially if the colony of rats you are dealing with is large. Some baits can kill after a single feeding, while others work more gradually.

While we have focused on Roof Rats and Norway Rats as being vermin and unwelcome, as unlikely as it may seem, these rats do have a positive trait. Due to their genes being 90% equivalent to that of humans, medical research on rats has allowed for many significant strides in the study of human diseases. These include cancer, Alzheimer’s, diabetes, Parkinson’s disease, and cardiovascular disease.


Having discussed at length the difference of Norway Rat vs Roof Rat and all the reasons for Norway Rats and Roof Rats being a wholly unwelcome and negative blight, we must bear in mind that many people’s lives in relation to their health have been improved thanks to the medical research that they have contributed to. It is somewhat ironic that these animals which we normally associate with causing disease, have contributed greatly to preventing disease too.

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