How to Hand Raise Baby Rodents
Introduction and Disclaimer
Recently I have found myself called upon for a familiar task - rescuing a litter of baby field mice. Their mother had been attacked by a cat and died from her injuries. She was found by a woman lying on the barn floor with her three babies still trying to suckle off her. After a public cry for help this woman got a lot of backlash before someone who knew me told me about the situation. Many years ago I bred fancy rats and a series of other pocket pets. Normally these animals are easy to breed and raise but I had a fondness for furless critters who often came with lactation problems. Before I knew it I had a new skill set - rearing babies on my own.
Currently no one in my area will take in baby mice or any other kind of rodent. Even certified wildlife rehabbers have no interest in this and seem to be constantly turning people down. There are a few reasons for this. For one rodents are notoriously hard to hand raise. They're very small, prone to aspirating, and depending on their age may need to be fed as much as every four hours around the clock. This is more work than most are willing to take on especially for something as inconsequencial as a mouse.
Another reason is a fear of disease. Rodents can carry strange parasites and viruses. They're responsible for helping the spread of rat scratch fever, leptospirosis, bubonic plague, haunta virus, and might even be helping the spread of lyme through diseased ticks they carry. It's a bad resume and since these things can't really be tested for it's always a risk when taking in wild animals. However not all these rescues are wild, some come from domestic situations and I think it'd be best to share my knowledge to help those who would like to take on this challenge. Obviously, before I get started, it is usually more ideal to find a foster parent with similarly aged babies to take on your rescues. Most rats, mice, and other rodents will take on the babies of others if you rub the smell of their own offspring all over the new ones. So if this is ever an option then it should be taken before hand feeding is attempted.
Once you have your little orphan or orphans you will need to set them up in a way that will keep them warm and safe. Often a small box stuffed with cloth, tissue, or paper based bedding will work well. If the babies haven't grown in their fur yet you may need to add a heat source to mimic what their mother would have been able to give them. Personally I prefer putting a heating pad under their box for this. Warm water bottles can also be used and I am fond of also adding a small stuffed animal to mimic the feel of the mother.
From here you'll need feeding supplies. You will have to decide if you are going to use milk, cream, or milk replacement. There is a lot of debate out there about what works best and why. Many rehabbers are adamant in using KMR - kitten milk replacement, which can be bought at any feed store. Personally I am not very fond of this stuff. The ingredients strike me as a lot less natural than good old fashioned milk and it's formulated for kittens who have vastly different nutritional needs. Regular cow's milk often get s araw deal because it's basically produced by a mama cow to fatten up a calf - sometimes by many pounds a day - also an unnatural prospect to a small animal. Milk may also contain horomones from the way it's farmed and not all animals create lactose in their milk like cows do. In fact if you feed a marsupial cow's milk this lactose intolerance will kill it. So if you happen to be hand feeding a baby possum or kangaroo do not use cow milk! Some people are really fond of goats milk. It's not as rich, though it still has some lactose. I'm on the other side of the spectrum. I think orphaned animals can often use richer food sources, especially when first starting off. My go-to is light cream, from a cow. I will probably get yelled at for the mere suggestion but this is what has worked for me in my experience. You may find something else works better for you.
From there you will have to decide which method you'd like to use to try feeding these babies. Most baby rodents are way too small to use easily available commercial nipples. This means you will likely have to use the Old School method of using a fine-tipped art paintbrush or the New School method I made up consisting of a 1cc oral syringe (which can be obtained at most feed stores) and a make up sponge.
The Paintbrush Method
I started with the paintbrush method probably twenty years ago when there was NOTHING in the way of resources for anyone attempting this. I was not the one who came up with it but I think I was the first to use it on rodents. It was a trick I learned from Old School finch breeders.
Basically you take the paint brush, dip it in warm milk or milk replacement, and gently put it in the animal's mouth. It should learn to attach to this and suckle the one or two drops off it which you can then remove, dip again, and repeat. The cons of this method are obvious - this constant re-dipping means you have to keep taking a nipple away after the baby has got a good sucking motion going. It interferes with normal feeding responses and takes you way more time. However the pros to this method is that since it is slower some may find it's a lot harder to aspirate the baby. Aspiration is when they take milk into the lungs instead of the stomach, often blowing it out their nose in bubbles. This usually doesn't kill them right away but within a few hours or a day, maybe even two, this opens them up to infection which usually does kill them. Lungs just aren't mean to breathe milk!
The Sponge Nipple Method
Currently I use a new method I devised using a 1cc syringe and a make-up sponge. I will take a make-up sponge, cut off a tiny sliver, cut it in the shape of a V, and then after filling the syringe with milk I will then insert the sponge into the end of the syringe with the aid of a sewing needle with the wide part in the syringe keeping it anchored and the thin part forming a primitive nipple shape. From here milk can be squirted out slowly while the baby is suckling one mouthful at a time off the sponge. I stress this must be done SLOWLY. Too fast and you'll have the same problem with aspiration I detailed above.
When you first start out you will need to take the baby, grip it's head firmly between your fingers, and try to place the paintbrush or nipple into its mouth. Keep in mind this is very hard at first. If they have suckled all from their natural mother their first reaction will usually be to completely reject your efforts. They can be really fussy and refuse to eat all together until they starve to death. This is especially problematic in the first 48 hours. I find it's better to let them get a little hungry and then try it again than trying to force them.
To encourage them further you will need to make sure the milk is warm. Normally they will not accept cold or room temperature milk. I have found the easiest way to accomplish this is to fill the syringe and then submerge it into hot water until its contents are warm. I test it on my wrist. You don't want it to be hot enough to burn.
One of the most frustrating aspects of hand feeding might be the little ones need to flail their paws, often pushing the syringe away from themselves. This is not them rejecting the syringe. It's actually how they encourage their mother to lactate more, by massaging her mammary glands as they suckle. Of course this often has the opposite effects when a human is in charge... and it can take quite some time to figure out to keep the nipple in their mouth while they're actively tying to push it away!
You'll need to use new milk, a washed syringe, and a new sponge or washed paintbrush, with every feeding to avoid bacterial growth which could kill them. If you're unsure if they're done feeding let them tell you. They may be falling asleep on you or perhaps they have stopped swallowing and are letting milk dribble everywhere. Another way you can tell is their bellies. If they don't have fur yet you can usually see a white band appear when they are full of milk.
If you're unsure how often to feed them here is a rough guide. Rabbits require only one feeding a day no matter their age. Rodents like rats, mice, and squirrels usually need feeding every four hours when they are infants, every 6 hours on their second week of life, every 8 hours on their third, and on their fourth they may require less or none at all. Depends on the individual animal (but milk soaked bread should be given as an option at this age either way. It'll reduce the work you'll have to do!)
Also remember that baby rodents do not have the ability to poop or pee on their own. This is something that will come to them in time but for their first few weeks of life you'll be responsible for emptying them out at feeding time. This is easily managed by taking a Q-tip, cloth, or sponge, dipping it in warm water and stroking their little butts from front to back like their mother would do with her tongue. They usually put up a pretty big fuss, might squeak a bit, but you'll soon see droplets or poop appear which you can then wipe off. If you don't do this they will suffer in the same way an older animal would from a total blockage. This will eventually cause them to fill up, go septic, and die. Not a pleasant way to go so please keep up on this!
After all this you should know that the first forty-eight hours are the most critical. This is when the vast majority of mortalities will occur. If you can get them past this you're doing great. If this is your first time trying and you've managed to get them past this then you're doing phenomenal. Like I said before rodents are really hard to hand raise. So don't be discouraged if at first you don't succeed. It even took me several attempts before I could get them past this first stage. Take pride in knowing you tried and if you succeed - you deserve a medal! or a piece of cake. Either way, you're doing great.