Mice: frequent questions


What’s the difference between a mouse and rat?
The easiest way to distinguish a rat and a mouse apart is by their size. For example, one of the most common rats, the Brown Rat (Rattus norvegicus), also called Norway Rat, Sewer Rat and other names, weighs up to 12 ounces (350 g), while an adult House Mouse weighs only an ounce (28 g) or so.

Mice have more delicate features and a more pointed snout. Their tail is thinner than a rat’s, which is thick and very noticeable. There are chromosomal differences, too, so they can’t interbreed although they probably had a common ancestor. They aren’t “friends.” In fact, rats will kill and eat mice.

Color drawing from an old book showing size and appearance comparisons between a Brown Rat, House Mouse and Rock Mouse.

Rat and mice comparison. (Biodiversity Heritage Library, NGS / Flickr; cc by 2.0)

Difference between House Mouse and Field Mouse
“Field Mouse” is a term used for several different mouse-like rodents, and not for an outdoor version of the House Mouse. In the U.S., it usually refers to the Meadow Vole (Microtus pennsylvanicus), which is larger than a House Mouse and has short legs, small ears, and a short tail. Coloration ranges from silver-gray to dark-brown. Voles belong to a different scientific family than mice.

House Mouse standing on the ground.

House mouse, Mus musculus. (Happy days 09 / Flickr; cc by 2

Meadow Vole standing on the ground.

Meadow Vole, Microtus pennsylvanicus. (Leo Papandreou / EOL; cc by-nc-sa 3.0) 2

Mice and diseases
Deer Mice are connected to hantaviruses, but the House Mouse is not. A study reported in New Scientist Magazine¹ shows that the greater the mammal diversity in your yard, the less chance that Deer Mice will be infected with hantaviruses. House Mice are associated with some other diseases, such as typhus or salmonella.

Your chance of contracting diseases from any species of wild mouse is low unless you put yourself at risk by handling them or inhaling their dried droppings. 

All mice should be respected for the important role they play outside, but promptly remove any that invade your home. If you happen to handle a mouse, be sure to wash your hands thoroughly afterward. Be aware, too, that mice may bite in self-defense. (Hopefully, you’ll trap mice humanely to be released outdoors. Don’t touch baby mice; mothers will kill those that smell of human scent.) 

About having a wild mouse as a pet
Have you trapped a wild mouse and want to keep it? They don’t make good pets. They’re nervous and skittish, can’t be easily tamed, don’t want to be handled, and getting away is always on their mind. There’ll be no pleasure in it for you, nor especially the mouse.

The best thing to do is release the mouse early in the morning, after feeding it some breakfast. Turn it loose into protective cover, such as tall grasses, a brush pile or undergrowth. If it was caught in your house, release it several blocks away (mice can be amazing at finding their way back home.) Thoroughly clean your hands and any areas the mouse has touched.

Mice are vermin … aren’t they? 
Well, our web name pretty much says it all — we’re all about wild-life, not wild-death. It’s our position that mice play an essential role in a backyard wildlife habitat, indeed nearly anywhere in the world, and should be left alone. Of course, we don’t want them in our homes, and when that happens they can be caught humanely and released outdoors.

Outdoors, there are non-lethal, common-sense ways to control rodent populations, such as eliminating potential nesting places and easy sources of food for them. A wildlife-friendly yard plays host to many predator animals that feed on mice, which helps to keep their population under control.

How to humanely remove mice from a house
Look for their trail of small, oblong, black feces along baseboards; this marks their traveling lane. Place a live trap baited with peanut butter along the trail. Some live traps are designed to catch only one rodent at a time, but traps are available that will catch and hold several at a time. (These require you to wind them up. When a mouse steps on a trip-bar, it triggers a metal plate which zips forward and scoops the mouse into a holding chamber. Take care not to over-wind; 10 turns is about right. (Our favorite is Ketch All Humane Mouse Trap.)

You can also try putting peanuts in the bottom of a deep bucket. Set the bucket on the trail and place a couple of boxes next to it to serve as steps to the top. Once in the bucket, if it’s deep enough, the mice can’t get out.

Release the mice at least one mile from your house, or they’ll find their way back (no kidding), and the second time around they’ll be smarter and harder to catch. Release them early in the morning so they’ll have a chance to get the lay of the land and build a nest before nightfall.

Release them into tall grasses, a brush pile, undergrowth or other conditions that will help shield them from birds of prey that search for mice from above.

*Wood Mouse, apodemus sylvaticus
¹New Scientist Magazine, July 4, 2009

More reading:

How to humanely remove other wildlife from people spaces   
Provide cover for safety, shelter