What should I do if I find an orphaned baby mouse?
Determine if the mouse/mice are indeed orphaned. If you have accidentally destroyed a nest with babies in it, build a makeshift nest using any of the nest remains in a small shallow container, and place it near the original nest site and leave it undisturbed for an hour or two to see if the mother returns to retrieve and relocate her babies. If any of the babies have already died, if they are lethargic or cold to the touch, or if you find one baby alone, chances are that they have been orphaned.
Always wash your hands thoroughly after handling mice.
The risk of contracting disease is rare but increases if you live in the southwestern United States.
When you find an abandoned mouse, there are a few essential steps that should be immediately taken.
(Please note - these instructions are also applicable for other small rodents like orphaned voles and rats)
The first priority is to get the baby warmed up before attempting to feed it anything. Baby mice with their eyes closed (and even for a week after eyes open) are unable to maintain their own body temperature without a supplemental heat source. Make a small nest using t-shirt material, flannel or fleece and place it in a secure container with ventilation (a reuseable Tupperware with vented lid works well) and place it on a heating pad set on low. Make sure it doesn’t have an ‘auto shutoff’. If you don’t have a heating pad, you can fill an old sock with rice, corn or another grain and microwave it for 30 seconds to use as a heat source (use good judgement to make sure it’s not too hot – you’re trying to mimic the mother mouse’s body temperature). This will need to be rewarmed every couple of hours to maintain the warmth.
While the mouse is warming up, use ahnow.org to locate wildlife rehabilitators in your area who may be able to assist in raising the mouse. Leave messages with as many as possible because you may not get a return call for several hours or days. Orphaned mice are VERY difficult to raise and require feedings every 2-3 hours around the clock for several weeks. Rehabilitators are already equipped with the proper tools, formula and knowledge to properly rehabilitate orphaned wildlife but they are very busy and usually overloaded with animals to care for, so be prepared to transport your mouse to them.
After warming, the mouse needs to be hydrated within a few hours of being found. Plain Pedialyte is the best option, but you can also make your own makeshift hydration solution by dissolving 1 tablespoon of sugar and 1 teaspoon of salt in 1 cup of warm water. The best tools for feeding mice are small syringes with pointed rubber nipples (example here), but you probably won’t have those on hand, so you can try dipping the tip of a tiny paintbrush in the fluid and allowing the mouse to lick it off. Get as much fluid into the mouse as you can (0.2-0.5 mL), every 2 hours for the first 4-6 hours.
Mice with their eyes closed need to be stimulated to urinate and defecate after each feeding/hydration session. Gently rub the genital area with a q-tip or tissue in a motion that mimics the mother mouse licking the area. Moistening the q-tip in warm water may help. Do this for about 10 seconds, and if no results, try again after feeding some more. You may not see any poop for the first few times, but you should hopefully see a few drops of urine unless they’re very dehydrated.
If you are unable to locate a wildlife rehabilitator after multiple attempts:
Baby mice can’t go too long without being fed, so if you’re not able to locate a rehabber within about 6-8 hours of finding the babies, you will eventually need to transition them from the hydration solution to a suitable formula. After 2 feedings of the hydration formula, you can start to feed watered-down formula, gradually making the formula to water ratio stronger over the next 3-4 feedings (for example, start with 5 parts water to 1 part formula powder, then 4:1, then 3:1 and finally 2 parts water to 1 part formula powder). For babies under 1 week old, I like to keep the ratio at around 3:1 or 2.5 parts water to 1 part formula so it's easier on their digestive systems. Acceptable formulas are: Goat’s Milk (or Regular) Esbilac Puppy Milk Replacer (this one is usually available locally at pet stores, Tractor Supply or even Walmart), Fox Valley brand formulas (20/50 squirrel formula; Puppy Formula), or if none of those are available, you can make homemade formula (3 tbsp goat’s milk, 3 tbsp plain yogurt, 2 tbsp heavy cream, 1/2 egg yolk. If you can't find goat’s milk, double the yogurt.) It's suggested that whichever of these formulas you start with, you continue with until the mice are weaned. They are very sensitive to change and switching formulas can cause diarrhea or death.
Powdered formulas are preferred because you can mix a fresh batch each day for the needed amount, in comparison with liquid formulas which must be used within three days. Please contact me for advice if you are having trouble locating suitable options. DO NOT FOLLOW OTHER ONLINE RECIPES FOR MIXING YOUR OWN FORMULAS WITHOUT GUIDANCE FROM A LICENSED REHABILITATOR – these can result in severe malnutrition and issues like bloat that can lead to death.
Baby mice need to be fed as often as once every two hours depending how old they are. (This chart can help to estimate age.) This means that you must be prepared for some sleepless nights. A good goal is to feed every 3 hours around the clock, and for the mouse to ingest between 0.3mL – 0.5mL per feeding (up until eyes open) and up to 1mL for eyes-open babies until they gradually wean at 3 weeks of age.
You can use the same method of dipping a tiny paintbrush into the formula and allowing the mouse to suck it off. However – this is a very difficult method of feeding small mice and usually results in the mouse not getting enough food at each feeding. Please try to order the proper syringes and small pointed nursing nipples for the best results.
After warming formula, gently hold the mouse between your fingers, with your index finger near the head, ready to prevent it from lunging forward and falling. Carefully and consistently apply pressure to the syringe plunger to administer 1 drop at a time and ensure that the baby is suckling and swallowing the formula.
TIP: Mice like their formula WARM and it cools very quickly in such a small syringe so it’s recommended to fill 2 syringes and have one sitting in a cup of hot water so you can swap back and forth regularly while the other one keeps warm.
Be careful not to allow any formula to enter their lungs. You can check this by observing that no milk is bubbling from their nose. If milk enters their lungs, aspiration pneumonia may occur. The best way to avoid this is to keep the mouse upright when feeding it, never allowing it to rest on its back. If you do see a bubble form, flip the baby to a head-down position to prevent any more liquid from entering its lungs and wipe the nose with a tissue to absorb any liquid.
Overfeeding is also dangerous and can lead to bloat. Check to ensure that they are well fed by the emergence of a white patch in the middle of their belly, a milk belly. This should recede before the next feeding. If you are seeing a full milk belly when the time comes for the next feeding, wait an extra half hour, and water down the formula to a 50:50 water to formula ratio for one feeding. If your mouse experiences diarrhea, it is also likely a result of being overfed. If this happens, or if your mouse is looking bloated, it’s ok to substitute Pedialyte/electrolyte solution for one or two feedings until the condition resolves.
Make sure to gently massage your baby’s abdomen and rectal area after each feeding to assist food in moving through the digestive tract and to help the baby eliminate waste. It’s almost impossible to reverse the effects of bloat once too much formula has backed up in the digestive tract, and this can lead to a painful death.
Baby mice begin to open their eyes at around 10-12 days of age. They may need a larger enclosure at this point (acrylic kritter keepers work well), but still keep using the heating pad on low under the nest portion of their tank. At this point, you can begin to add some dry oats into their nest and they will start to nibble on these within 1-2 days. Once they start nibbling solids, they will no longer require a nightly feeding – they can last from midnight to 6am without formula.
You can start to introduce other soft solids like spinach and other greens, fruit and crushed nuts. At three weeks of age, the babies will also no longer require the syringe for feedings and may begin to feed from a dish (jar lids work well as shallow dishes). Gradually make the switch from the syringe to a dish by leaving a dish of formula available between meals and spacing out feeding times to every 4-5 hours.
You can begin integrating foods such as baby food, fresh fruits and veggies, seeds and commercial mouse foods. Make sure to add a shallow dish of fresh water.
Mice are often very messy eaters, so after they finish their meals, it will be necessary to clean them up and replace soiled cage bedding often. Plain paper towels make for easy clean up when used to line the cage. Alternatively you can use an unscented shredded paper bedding made for rodents.
By this point, your babies will be getting more active so you can move them to a larger tank – a large acrylic kritter keeper or 10 gallon tank with a tight fitting screen lid are best. A wheel for exercise and some places to hide and things to chew on are also good for enrichment.
Mice can be released at about 4 weeks of age – about 1 week after weaning. However, it’s often better to keep them for an extra week if possible to allow them to put on some more weight. To begin acclimating for release, ensure that the weather is consistently above 50 degrees Fahrenheit and that there are at least 3-4 days with no rain forecasted*. A suitable release location should be an area with plenty of underbrush for shelter and nearby food and water sources.
It’s good to move their cage outdoors in a protected area at least a full day before release so they can adjust to the outdoor smells and sounds. Secure the lid so no predators can intrude overnight. Mice should be released at dusk since this is when they are most active. Gently tilt the tank on its side and gradually open the screen cover. Continue to place food and water at the release location for at least a week, if not longer, while they establish a nesting site nearby.
*If the mice are old enough for release but it’s too cold outside or if heading into the winter months, you may need to overwinter the mice until spring. Please visit the Adult Mouse Care page for further instructions.