Adult Mouse Care

If you have hand-raised orphaned mice, or live-trapped adult mice, and it’s too cold to release outdoors (temperatures consistently below 50 degrees Fahrenheit, or heading into the winter months), you will need to provide a safe environment for them until the weather is suitable for release.

NOTES REGARDING TRAPPING:
If you plan to live-trap mice in your home or garage, it will be pointless unless you can determine the point of entry and seal it up. Mice leave scent trails leading to the entrances of their nesting areas, and if you trap mice and release elsewhere, that will not stop other mice from finding the entry points and continually infesting the same space.

Check around the foundation of your home and look for holes that have been drilled for cable and phone line access. Often the hole is larger than the cable and the space around the hole can be sealed with caulk to prevent mice from entering. Any cracks in the foundation, or around doors or windows that are the size of a dime or larger can allow mice to enter – so seal these up before beginning your trapping efforts.

The following are some recommendations for effective live traps:

HOUSING ADULT MICE
Determining Gender

An important step before setting up a long-term enclosure for your mice is to separate them by gender – otherwise you may be housing MANY more mice than you planned on. This may be relatively simple if you have hand-raised them as orphans and the mice are handleable. However, with wild-caught mice this may be a bit difficult.

A suggested method is to transfer the mouse from the trap to a clear container with a lid so you can have a look at the underside of the mouse (acrylic keeper, empty glass tank, or they may willingly climb into a glass jar if you set one into a bucket-type trap with the mouse). It’s recommended to make any transfers in an enclosed, escape-proof location like a bathroom (inside the bathtub is best since it may slow them down if they do end up escaping somehow).

You will need to look at the lower belly region. The males have more space between the anal and gential area than the females. The male will have some slightly raised patches (often covered with white fur) on either side below the penis where the testicles are. This is much easier to see on an older male.

Females will have only a slight protrusion at the genital area and it’s a lot closer to the anus. You may also notice 2 indentations on each side of the lower belly above the genitals (at about a 45 degree angle) – these are the nipples on the female. She has more sets of nipples higher up on the belly which are sometimes visible. On newborn, hairless mice, this is the easiest way to determine gender since the males don’t have any nipples and they appear as small dark dots on the female’s belly.

Setting up a cage

Once separated by gender, mice of the same sex can be housed together if they are siblings or have been trapped in the same house. You can often house unrelated female mice together with no issues, but mature adult male mice who are unrelated may fight, so it may be best to separate them.

Glass aquarium tanks with fitted metal screen lids are the recommended type of caging. Screen lid clamps are available for added security. You may also use hamster-style cages, however the bar spacing should be no more than ¼” to prevent escapes (NOTE: these type of cages are often difficult to clean if you have wild mice who may try to run out of the cage when you reach inside).

As a general rule, no more than 4 mice should be kept in a 10G aquarium, but 2 is ideal to prevent overcrowding. The larger the cage you’re able to provide, the better. For cage bedding, a shredded paper bedding, such as Carefresh, is ideal. Aspen shavings can be used, but pine and cedar emit harmful vapors that can interfere with the mouse’s respiratory system.

Cage Décor

You should provide some areas for the mice to hide and build a nest. It can be as simple as a small overturned box with a hole cut in it. You can also use commercially available hide-outs made for mice or hamsters. Adding some polyfill and giving the mouse some tissues to shred will give them something to build their nest out of.

A running wheel is a MUST for any captive mouse. In the wild, they may run a combined distance of several miles per night, so the wheel provides an outlet for their energy. A 6-10” wheel size is best.

Other cage decorations can include:

Cardboard toilet paper rolls
Sticks, twigs and pinecones from outside
Woven grass tunnels
Ropes
Ladders
Any other cage décor sold for mice and hamsters.

Food & Water

Food dishes can be as simple as a jar lid, or you can use shallow crocks sold for mice and hamsters. For water – mice are notorious for making a mess of their water – they will poop in it and tip over the dish and/or fill it with bedding, so it needs to be monitored closely. A good solution for a water reservoir is this small ceramic ‘igloo’ which holds 4 oz. of water and will not tip over. You can also try using a free-standing water bottle although it may take a wild mouse awhile to learn to use it.

You can offer your mouse a variety of foods that you may have available in the house, or you may purchase commercially available mouse foods. However, wild mice are often picky eaters and prefer to have their available food options rotated on a daily basis. It’s a good idea to purchase some vitamin drops to add to water or food to make sure they are getting the nutrients they need.

Some food suggestions are below, and specific ones listed have been found to be more readily accepted, but you can experiment because every mouse has individual tastes. All foods should be served raw unless otherwise noted, and it’s helpful to chop larger fruits and veggies into smaller pieces.

Fresh fruits & vegetables (excluding garlic, onions, hot peppers, and gassy veggies like cabbage and beans)

Avocado
Corn (cut a few kernels off the cob)
Zucchini tops (include the stem)
Bell pepper seeds (include the pithy part)
Fresh peas
Spring mix, spinach or kale
Berries
Pomegranate seeds
Grapes
Peaches

Other foods:

Vanilla Yogurt (dairy or coconut milk) is a favorite and perfect for adding vitamin drops to.
Fruit/veggie pureed baby food
Freeze dried or cooked, unseasoned chicken or turkey
Freeze-dried grasshoppers or mealworms (sold for reptiles)
Unsweetened cereal (like Cheerios)

Seeds, nuts and grains (all unsalted):

Sunflower seeds (with shells preferably)
Pumpkin or squash seeds (dry out in oven)
Chia seeds
Millet
Bird seed mixes
Peanuts (roasted), almonds, walnuts, pecans, hazelnuts – chopped into pieces
Rolled Oats
Shredded unsweetened coconut

Cleaning

Sometimes the mice will choose one corner as a ‘toilet’ and this makes it easy to regularly remove soiled bedding in that area. Use gloves or wash hands thoroughly after removing soiled bedding, and avoid breathing in dust particles from the tank (illnesses can be transmitted through the urine and feces, although rare).

You will need to replace all bedding every 1-2 weeks depending on the number of mice. The wheel and other cage décor should also be removed and washed in hot soapy water on a regular basis. It’s recommended to do this during the day while they are asleep in their nests. Moving the tank into a bathtub, and keeping the tank covered with the lid as much as possible while you remove and replace sections of bedding will help prevent any accidental escapes should you startle the mice while cleaning. They are very fast and can jump remarkably high. The slipperly sides of the bathtub can slow them down while you contain them - so always have an empty Tupperware ready just in case.

Preparing for Release

Once the weather has warmed up again and nighttime temperatures remain above 50 degrees Fahrenheit, you can choose an appropriate release location (lots of ground cover and access to natural foods and water). It’s suggested to leave the cage outdoors for a day or two in a sheltered location (with tank secured from predators) so the mice can adjust to the temperatures, smells and sounds of the outdoors. After acclimation, wait until dusk when mice become most active, and carefully tilt the tank on it’s side. Remove the cover and allow the mice to leave when they are ready.

Leave the tank in place for several days to make sure none are still returning to sleep there during the day. Provide food and water for at least a week after release until they can search out natural food sources.