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Roof Rat vs House Mouse: Which One Has Invaded Your House?

Updated on: December 28, 2020

There are typically over 100 different bugs and other animals living in your house, with the vast majority of them passing through or barely making their presence felt. Others, like roof rats and house mice, are much more of a pest that needs to be dealt with before they become a huge problem.

But how do you know if you’re dealing with roof rats or house mice? Roof rats are generally bigger and avoid human contact, while house mice are small and curious. Knowing the difference between the two can help you better get rid of them, and identify the factors that caused them to nest in your property to begin with.

Roof Rats, House Mice, And Norway Rats: Rodents To Look Out For

There are three common species that invade houses in the United States. Here’s a table that can help you tell them apart:

Roof RatsHouse MiceNorway Rats
Medium-sized (typically around 10-12 inches long)Small (typically around 5 to 7
Inches long)
Large (typically around 13 to 18 inches long)
Large ears, large eyesLarge ears, small eyesSmall ears, small eyes
Tail is longer than head and body combinedTail is longTail is shorter than heady and body combined
Pointed nosePointed noseBlunt nose
Typically gray-colored with some black shadesTypically light brown with some gray shadesTypically dark coats with lighter shades on the underside of the body and tail
Pointy droppings, around ½ inch in lengthPointy and scattered droppings, around ¼ inch in lengthBlunt and thick droppings, around ¾ inch in length

Anything larger than your average hamster is most likely a roof rat; anything smaller is a house mouse; and large, kitten-sized rodents are most likely Norway rats.

There are several things that can put your house at risk of being invaded by any of these rodents:

1. An unsecured food source

Rats are particularly drawn to unsecured or readily-available food sources, such as food cabinets or hanging baskets. Even small stashes of food can be enough to sustain a small colony of rodents. Most rodents aren’t picky about food and will dine on anything available including leftovers.

Food sources don’t have to be inside your house – or even something that you eat yourself – to support a rodent colony. Roof rats in particular will eat seeds, nuts, berries, and other garden produce when given the chance.

2. Plenty of ambient heating

Rats like to make their homes near sources of heat, since their nests can incubate better when it’s warm. If your home uses plenty of in-wall or in-floor heating, you’re more likely to be invaded by rats. Rodents can burrow surprisingly deep inside walls, attics, or ceilings, which can make tracking down and getting rid of their nests difficult.

The weather and climate also play a significant role: rats are more likely to seek shelter and settle in houses during the winter or rainy seasons. The combination of the cold weather outdoors and the increased amount of heating you use inside are ideal conditions for a rat colony to form.

3. Old or damaged structures

Any part of your house that’s exposed to the elements, left in disrepair, or badly constructed are all potential entry ways for rats. Since rats can migrate easily from one place to another, any unsecured entry point can potentially let a breeding pair inside your home.

These entry points can also include places like vents, drainage pipes, and electrical conduits. If there’s a direct line from your house to the outside, you should assume that it’s a potential entryway for rodents.

When Is It A Roof Rat?

Roof rats usually invade homes through power lines, adjacent trees, and even houses next door. Since they’re good climbers, they usually don’t leave any traces of their presence until their colony has grown large enough, or if the people in the house manage to catch sight of them.

Here are some signs that you may be dealing with a roof rat infestation:

  • Loud squeaking or scratching noises: because of their tendency to climb and burrow through homes, roof rats can be quite loud, especially during the evenings.
  • Plenty of rat droppings: roof rats don’t bother concealing their droppings, especially if it’s near a food source.
  • Half-eaten or chewed fruit: roof rats have a strong preference for eating fruits, and will usually settle near shrubs, fruit trees, or unsecured fruit baskets.
  • Chewed or gnawed areas near the ceiling or attic: while roof rats can make their nests inside walls that use heating systems, their preferred places are usually around the top of your house where there’s plenty of ambient heat.

As nocturnal animals, roof rats are most active during the mid-afternoon to early morning. But if you have a large enough colony, you’ll most likely see a few of them out and about during the day.

They prefer to stick to higher places in your house, like ceiling beams or on tops of cabinets. Extremely agile and excellent climbers, they can move along railings or wires to their nest or food source. While they can frequent areas that are frequently out of reach, they are creatures of habit: their paths are easy to trap once you’ve found them.

When Is It A House Mouse?

Small and unobtrusive, house mice are relatively easy to spot despite their size. While they aren’t as agile as rats, they’re just as good with climbing, burrowing, jumping, and swimming. This makes their reach slightly wider than roof rats.

Here are some signs that you may be dealing with a house mouse infestation:

  • Strong, ammonia-like smell: house mice will often pee near food sources or nesting sites. Their urine has a distinctive and strong musky odor that lingers for days, which can make their usual routes easy to spot.
  • Chewed-up newspapers and boxes: aside from nibbling at food packs, house mice also prefer to build their nests with soft materials like paper or cardboard.
  • Plenty of small, scattered droppings: house mice will often leave droppings around their frequently-passed routes, with around 50-80 pellets a day.

House mice are also nocturnal, though they can move around in the day when they need food. They’re also bolder than roof rats, and will make no attempt to hide their presence even if you spot them.

One thing to note about house mice and roof rats is that house mice are naturally afraid of roof rats, so it’s unlikely that you can have both of them at once in your home. House mice are considered prey animals by roof rats and will avoid areas that have roof rat droppings in them.

Dangers Of Infestation

Regardless of the species, leaving a rat infestation unchecked can be dangerous and potentially lethal. Rat colonies can grow and multiply in a span of weeks, and can easily overrun your house if you don’t take steps to remove them.

Here are three of the biggest dangers that rat infestations pose to a home:

  • Property damage: damaged electrical wiring, chewed-through insulation, and holes in your walls
  • Risks to pets and children: rats may attack your pets or children if they feel threatened
  • Food contamination: as carriers of disease, the proximity of rats to your food means you’re in danger of catching serious illnesses

These dangers can effectively compound the bigger the colony grows, which is why it’s crucial that you treat an infestation right away.

How To Get Rid Of Roof Rats And House Mice

If you have seen roof rats or house mice around your home, there are a few things that you can do to deter or even wipe out the infestation before it grows too big to control.

1. Target nesting sites

Clearing out nesting sites like the attic and wooden storage boxes are excellent ways to dissuade rats from nesting and breeding. Once you’ve removed most potential nesting sites, they may be encouraged to move on due to the lack of places to breed.

2. Take away food sources

Check for unsecured cabinets, garden plots, or stagnant water sources near your home. Even small deposits of food and water are enough to sustain a growing rat colony. Investing in airtight containers and closed off-wall shelving can help restrict rat access to your food.

3. Trap frequently-traveled areas

Once you’ve managed to establish where rats are coming from, you can start trapping these areas to catch them. Take note that rodent behavior differs with traps: roof rats are cautious and will usually try to navigate around any traps you place, while house mice are more likely to walk into them to investigate.

4. Hire professionals

If you aren’t confident about your rat-trapping capabilities or think the colony has grown too large for you to handle, then you should hire a pest removal or rat extermination company to take care of the problem for you. They have all the tools and experience needed to remove infestations of all kinds, and can give you recommendations so they don’t happen again.

Control Pest Infestations With PermaKill Exterminating

Learning the difference between roof rats and house mice can give you insights into their behavior, which can make it easy to deal with infestations before they get too out of hand. Even if you’re hiring a professional, keeping tabs on rodent habits in your home can help your pest removal company with possible extermination methods.

If you’re dealing with a rodent infestation that you want gone, call PermaKill Exterminating today for an on-site consultation.

Read more: How to Get Rid of Rats in Yard Without Harming Pets


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