Care

Introduction to mouse care

There’s a lot more to know about keeping mice as pets than many people realise. There are loads of resources on the web about caring for your pet mouse, but who ever heard of too much information? So here’s my how-to of keeping mice, gathered from nearly 25 years of experience, as well as from other resources along the way. If there’s anything I’ve missed that you think should be included here, or you have any questions regarding keeping mice, please feel free to contact me.

Before I start, I can’t emphasise enough the importance of finding a good small animal vet before you purchase your first mouse. Mice can get sick very quickly, and you don’t want to have to play games, running around to different vets, when you have a sick pet. People will probably laugh when you tell them you spent $100 on a vet bill for your mouse, and ask you why you don’t just buy a new one. But stay strong. A mouse may be small, but it is just as important as a cat or dog in your family. If you’re not prepared to spend money on the health and wellbeing of your mouse, please do not get one. It’s just not fair on the small creature that relies on you.

One mouse or two? Boys or girls?

Boys

Boy mice are territorial, which means they usually won’t accept other boys into their space. They can be kept singly, so if you only want one mouse, then you want a boy. In my experience, a single boy bonds more strongly to you, and makes a fantastic, interactive pet. Boys tend to be bigger, and live longer than girls, but they also tend to smell a bit more too.

Boys can also be kept in pairs or trios as long as they are brothers, or were introduced at a young age. I have great success keeping my boys in groups, although there is an element of risk to it. See the next section for more information on keeping boys together.

Girls

Girl mice are social animals, so you must get two or more girl mice to live in a community cage. Unlike with boys, girls can accept new mice introduced at any time, although it does depend on the personality and dominance of the adults – some girls can be quite territorial as well, and take a while to warm up to new additions. Most pet owners seem to find they want girls – I think the fact that they smell less tips the tables. Because of this, girls are usually harder to acquire than boys, so you may find yourself waiting longer, especially if you want to buy a group of them.

Can I keep multiple males together?

Yes. But it can be tricky. The key to keeping males together is to purchase two or more brothers at the same time. As long as they are never separated, they should live together relatively peacefully. There will usually be scuffles and dominance struggles, especially when you clean their cage, but as long as no blood is drawn, there is no need to separate them. If your males do seem to be at war more than peace, try and make the cage bigger, and include a house, wheel and food dish for each male so they don’t feel the need to fight over territories. Another good tip is to clean out their cage in sections – do the toys one week, and the litter the next, so there’s always something that still smells like them.

I have successfully kept pairs, trios and even a few large groups of boys together in appropriate-sized cages and have even separated one member of the group to breed, then reintroduced them successfully. I found that going half a day with the boys and half a day with the girl for a few days both kept him familiar enough in the bachelor cage so as not to be attacked, and managed to get his girlfriend pregnant. However, I would only attempt this with a group of boys that were very well established.

Finally, boys tend to go through a sort of puberty at about 6 months old. Some groups can get much more territorial at this time, and I’ve had moderate injuries sustained during this hormonal period. I find that less frequent cage cleans help as they don’t need to constantly re-establish territory. Also, try to treat both mice equally. If one gets picked up, the other gets picked up. Multiple bowls etc as stated above is also useful. All that said, sometimes even brothers cannot remain together forever, and if boys are going to need to be separated permanently, it’s usually round this time.

Whether your boys will remain together with some minor scuffles, or need to be separated for their health and wellbeing, comes down to a common sense decision. Don’t risk the lives of your mice through stubbornness.

Where can I get a pet mouse?

Rescue a mouse

What better way to start your pet mouse obsession than to save a life? Ask at a local animal shelter if they keep abandoned mice. Many won’t, but should be able to direct you to a small animal rescue. There are often young animals available for adoption, as females are sometimes abandoned already pregnant. Many breeders also rescue and rehome unwanted mice. Try the RSPCA or Porsche’s Small Animal Rescue.

Buy a mouse from a breeder

Finding a good mouse breeder is a great way of ensuring you a well-adjusted, healthy pet. In NSW you can try the Australian Rodent Fanciers’ Society of NSW, or the Australian Rodent Club. In Qld there is also the Queensland Rodent Fanciers’. Often the best way to choose a baby mouse from a breeder is to attend a Club Show and choose one yourself.

If you can arrange it, it’s a great idea to visit the breeder at their home and ask to see where the mice are kept. If the breeder is worth his/her salt, they will also ask you a dozen questions about why you want a mouse, how you will keep it, and so on. Watch out, though, because some breeders are no better than mass-producing mouse factories, and have little regard for the health and temperament of their babies. If something doesn’t sit right, or you visit their mousery and it’s unclean, overcrowded or their animals look sick or unhappy, then find another breeder.

Buy a mouse from a pet shop

Perhaps the easiest place to find a mouse is your local pet shop, but this is hardly the best. Some pet shops do keep healthy animals on the right litter and give the right advice, but they are few and far between. Too often I see poorly socialised, unclean and badly fed animals in pet shops – and that’s the animals that they’re selling for pets, not food. Mice that are sold purely as food for snakes are rarely happy, healthy animals, and are usually kept in mixed-sex bins. This means that if you do decide to purchase a female from a feeder bin, she will almost definitely be pregnant. If you feel you have no option other than to get your mouse from a pet shop (or fall in love with one particular mouse when passing through – we’ve all done it), then make sure you rad through the “How do I choose my new mouse?” article, below.

How do I choose my new mouse?

Regardless of whether you choose a pet mouse from a rescue, a breeder or a pet shop, there are certain things you should always look out for.

  • The animals should be alert and healthy-looking, with no breathing problems, sneezing, injuries, scabs or scratching, weeping eyes or diarrhoea, with a full, healthy coat and bright eyes.
  • The enclosure should be suitable, that is, not overcrowded, with ample hideaways and clean food and water, the area should be relatively clean of waste and should not smell too much. Check what type of litter they’re being kept on (more info on this here).
  • The mice should be kept separated by sex (if they’re not, females will likely be pregnant) – in some places, not separating males and females is actually against the law, so this is important.
  • Ask whether they sell the mice for snake food – if they do, it tells you they probably won’t put a lot of care into keeping them happy and healthy.
  • Ask about the history of the mouse – where did it come from? Do they know anything about the parents? If so, were they healthy and long-lived? How old is it? If female, was it separated from its brothers by 5 weeks old, to ensure it is not pregnant? If it is from a breeder, does it have a pedigree?
  • And finally – perhaps most importantly – make sure you handle the mouse before purchasing it. The most beautiful, healthy mouse is the world will do you no good as a pet if it is not friendly.

What’s the difference between a feeder mouse and a fancy mouse?

A mouse is a mouse is a mouse. Whether it was bred with the intention of being lunch or someone’s pet doesn’t make a difference – it’s not a different species or anything. Generally, but not always, feeder mice are albino and often they are bred to have larger litters to better feed your snake. Generally they aren’t handled very much, therefore they usually aren’t as tame as those destined to be pets. Depending on the source (ie. a bad feeder breeder), they can be poorly bred and have physical or behavioural problems. But, then, some fancy mice breeders are just as bad with this, and some feeder breeders have excellent practices. So, in conclusion, that’s a whole lot of generally’s, usually’s and often’s. Just find a mouse you like and go with it.

How intelligent are mice? Can I teach them tricks?

I find my mice to be very intelligent, for a small animal. I’ve heard it said that they are more intelligent than hamsters and gerbils, though we don’t get those here so I can’t say from personal experience. When I enter the room, my mice will almost always pop out to say hello and often rally at the cage door waiting to be paid attention to. I have heard of people training their mice to do simple tricks, come to their names, etc with the use of large amounts of repetition and treat rewards. I haven’t done this myself as I prefer my mice to behave as they want to, not as I think is cute. Remember, mice are used in laboratories all over the world to study behaviour, run mazes, hit coloured buttons that lead to food – all this indicates a certain level of intelligence.

What kind of cage should I get?

Wire mouse cage

Probably the most common type of cage you’ll find; there are hundreds of different brands and types of cage you can buy from pet shops or online. There is ample ventilation, the mice love climbing on the wire walls, and it’s super easy to attach toys all over the place. The only down side I can think of is that some of these cages have only a tiny access door, which can make it difficult to catch a less friendly mouse. I also find them a bit of a chore to clean, especially as they get older and the powder-coating chips away.

Aquarium or terrarium

Aquariums can make excellent enclosures for your mice because they come in all sizes, are easy to fill with toys and easy to keep clean as no smells will sink into the glass. They are also good for people with cats, as they are too heavy to be knocked over, and with the right lid, will safely withstand a curious cat on top too. The main down side to an aquarium is that there is little ventilation and in the summer can literally cook your babies if you don’t take the right precautions. Using a mesh lid can allow some circulation, but make sure the mice can’t chew through it – you’d be amazed how high they can jump!

Plastic S.A.M/Habitrail type cage

These cages are really popular with the novice pet mouse keeper, though I wouldn’t want to have more than one to clean. They are great to look at, colourful and fun for your mouse, but all those tubes and compartments get really icky really fast. After a few weeks of scrubbing pee out of those tubes, you might change your mind about how cool they are.

Home-made

Certainly the cheapest type of enclosure, many people forgo the expensive pet-shop-bought enclosures for a simple plastic tub. Basically, you buy a large tub from Kmart, cut out the top and cover with fine, metal mesh. Then, drill holes for the water bottle or hanging toys, and fill with whatever your heart desires!

How big should my cage be?

As a general rule: the bigger the better! Use your common sense. Think about how big you are, and how big your house is. Now imagine you’re the size of a mouse, and think about how much space you’d like to live in. My single boys get a cage with floorspace about 45cm by 30cm. I personally wouldn’t keep any mouse in less space than that – though I might keep up to 3 in that size. I don’t think 1 mouse needs less space than 3 mice – so if you think your cage is too small to comfortably house 3 mice, then it’s probably too small. If you’re stuck for space, then go vertical! Shelves, ropes, hammocks, hanging toys, all add to a mouse’s environment, without necessarily taking up more room.

What kind of litter and bedding are best?

Recycled paper pellets

This is what I use for my mice (the brand is called Breeder’s Choice here – in the US I believe it is Yesterday’s News) as it is relatively cheap, easy to obtain (the supermarket has big bags) and totally safe. There’s no toxins or aromatic oils to worry about, it’s safe to be chewed on, and my mice love digging through it. There are also types of compressed paper litter (such as Healthy Pet, or Carefresh) that looks like little chunks of mashed paper pulp. This is even softer on little mice feet, and it’s quite light, so mice tend to enjoy making tunnels underneath it if given enough.

Hemp shavings (Agrisorb)

A very popular choice with breeders, for the combination of smell control and absorbency. It looks like wood shavings, but is actually made from hemp, instead of the more common aromatic pine or cedar shavings. An added bonus of hemp is that it’s naturally anti-fungal and anti-bacterial. If you don’t mind buying in bulk, then this is a great one to try.

Chaff

A natural alternative that looks natural and smells great. I love this stuff as an additive to bedding, but I personally found it not terribly absorbent as a litter. My mice also ate a lot of it, which is not awesome for a floor-covering. Many people do swear by it, though, and it’s cheap! Wheaten chaff, if you can find it, seems to be the type people like the most.

Shredded paper

Your mice will have a great time burrowing and nesting in a big pile of shredded paper. Just make sure the edges are not sharp, and the ink used on it is not toxic. However, it’s also not terribly absorbent, so I would recommend using it in conjunction with another type of litter.

Lucerne

Lucerne can be used in the same way as shredded paper – a pile placed on top of regular, absorbent litter in the bottom, will be loved for nesting and exploration. It has a nice fresh grassy smell, and my mice can make the most amazing constructions by weaving it together. Keeps them busy for days!

Wood pellets/shavings

I would personally advise to stay away from any sort of wood-based litter product. Many people say it’s fine to use pine as long as it’s kiln-dried and dust extracted, and I have known people to do this successfully, but personally I think why risk it when there are alternatives. The aromatic oils in pine and cedar irritate the respiratory systems of small animals, and can lead to respiratory infections. These can be treated, but in some individuals it can become a chronic problem and stay with them for the rest of their lives. The only absolutely safe type of wood litter is aspen, but this can be hard to find and expensive. If your pet shop or breeder keeps their mice on shavings, ask them what type it is. If they don’t know, it’s probably pine, and any mice you buy from them will most likely come with irritated respiratory systems. I have experienced this on multiple occasions and it is notoriously difficult to cure.

Kitty litter

Clay-based kitty litter is another no-no. The clay is dusty and can irritate little mousey lungs, and they will eat it, potentially causing blockages. That said, before I knew better, I used kitty litter for all my mice (this is many years ago) and never had so much as a sneeze. Again, it’s a case of better safe than sorry – stay away from it if you can.

Would my mouse like some toys?

Yes! Mice are very active animals and crave stimulation. There are plenty of different toys available at pet shops (check the bird toy and cat toy section as well). Anything that is safe to be chewed at (hard plastics are generally ok, but stay away from soft rubber or anything that looks like it could be eaten) will be played with. I also love going to discount shops and buying anything with a hole in it – from plastic kids toys to kitchen- or bathroomware to oil burners.

Wheels

There is one toy that must never, ever be passed up – the trusty mouse wheel! No mouse house is complete without a wheel. I prefer the type that is enclosed, with a running surface that is solid plastic, so Mrs. Mouse doesn’t have to worry about getting her feet or tail caught in the bars. Ideally the wheel should have a diameter of at least 15cm, smaller than this and you’re risking wheel-tail, a condition where the tail is stretched out of shape from having to hold it over the head to run in the wheel. I especially love the “Silent Spinner”, “Wodent Wheel” and “Flying Saucer” wheels.

Toilet rolls

There is little that beats the good old toilet roll. Pile a few together to make a toilet roll castle, or hang them from the walls or top of the cage with wire. They’ll get chewed to pieces for nesting material, and just for fun. Easy to replace them whenever they get destroyed!

Plastic tubes

Companies like S.A.M and Habitrail make add-on tubes and houses to go with their cages, but you can buy them separately and just use them as tunnels in the cage – mice love tunnels. For a cheaper idea, go to a hardware store and buy PVC piping to use instead.

Ropes

Thick ropes strung across the cage are an exercise in balance. You can buy sturdy colourful ropes from pet shops as a bird toy that attach to the cage bars, or just make one yourself by plaiting strips of fabric or thinner rope.

Mouse balls

Another thing that many mice enjoy is the mouse ball. Pop him in and watch him run around the room in the safety of the ball. Some mice don’t ‘get’ balls – don’t force them. Most will love it, but let them tell you whether they do or not before sticking them in every afternoon.

Food toys

Loosely scrunched up balls of paper with some food in the middle make for hours of entertainment. Or thread bits of food onto some thin wire and string it across the cage for some climbing fun. Cat balls also sometimes have room for a treat or two to be pushed inside, and your mice will go nuts trying to get it out.

What should I feed my mouse?

Mouse muesli

You will find basic seed mixes sold at the supermarket or a pet shop. Many people simply give this mix, and it is sufficient to keep a mouse happy. However, I like to add a few things to make the mix more interesting, and a little healthier and more balanced.

These should form the base of your mix:

  • Wild bird seeds
  • French millet/budgie seeds
  • Guinea pig seed/pellet/lucerne mix
  • Uncooked, plain rolled oats
  • Dog kibbles (less than 20% protein if possible – I use the ‘Senior’ type)

These are good to add in smaller quantities or for variation:

  • Uncooked pasta
  • Uncooked brown rice
  • Rice/wheat/corn puffs (from the health food section – no sugar or preservatives)
  • Cooked and dried chickpea snacks
  • Linseeds
  • Pumpkin seeds (pepitas)

Lab blocks

A complete balanced diet – it’s what they’re fed in research labs, which is why they’re called lab blocks! Many people swear by them, as it means the mice can’t pick and choose what they want out of their mix. They are also a bit boring. If you want to use lab blocks, your mice will especially enjoy some variation in their treats and fresh food, as outlined below. There are various brands of lab blocks out there, some good brands to try if you can find them in your area are McManus Cummins, Laucke Mills, or Norco.

Fresh fruits and veggies

Some mice love fresh fruits and veggies – others don’t. Experiment by giving them little slices of carrot, broccoli, cucumber, celery, sweet potato – be creative. Avoid iceberg lettuce as it tends to give mice diarrhoea. Fruits should be given in moderation as they are high in sugar, but I’ve found that apple, grapes, pear and melon are quite popular.

Baby food

Good quality baby food (check the ingredients to make sure there’s no colours, preservatives, salt or sugar added – I like the organic ones) is also an excellent treat and I’ve found that even with mice that don’t like fresh veggies, they’ll all dig in to some baby food. The best flavours, in my opinion, are the plain veggie ones, or the meat and veggie dinners. Plain egg custard is also a popular one for a treat. A good way to get your mouse to like you is to put a bit on the end of your finger and let him lick it off. Prepare to be nibbled, though!

Leftovers

Mice have a pretty similar dietary requirement as humans – they can eat most of what we can. Crusts from your toast in the morning, mushy Weetbix leavings, scraps of scrambled eggs or omelette, leftover rice or pasta – they’ll eat it all and love it. Remember to clean out any uneaten food before it goes bad though!

Do sick or pregnant mice need special food?

Sick, pregnant or nursing mice work hard to overcome illness, or produce babies – so giving them extra high protein, high nutrient food will help them recover faster and stay strong and healthy. Here are some ideas for bonus food:

  • Nutrigel – a delicious, nutrient-rich gel sold in pet shops
  • Eggs – scrambled, boiled or even raw – egg shell is high in calcium too!
  • Meat – small pieces of cooked chicken or canned tuna/salmon are best
  • Yoghurt – this helps establish the gut bacteria, and it has been shown that a mouse that eats yoghurt while pregnant produces healthier babies
  • Avocado – high in good cholesterol and fats (don’t give the skin as it’s toxic – only the flesh)

I think I bought a pregnant mouse, what do I do?

It happens to almost anyone who buys a female mouse from a pet shop, and it’s a risk you need to accept if you choose to go that route. Pet shops are notorious for not separating boys and girls, either accidentally or because they don’t particularly care. I’ve even come across more than one pet shop who purposely leave boys and girls together so that any female mice they sold would have babies to be returned to their shop as more stock.

If you’re concerned about your mouse being pregnant, there are some things to check for.

  • Double check the sexes of your mice. The shop may or may not have sexed them correctly. See sexing pictures further down this page.
  • If you find you have mixed sexes, you need to make the decision to return one sex, or separate them into same-sex cages (remove the male ASAP regardless, on the chance that he hasn’t gotten her pregnant yet). You cannot keep males and females together for the long run because they will breed constantly (ie. a litter every 3 weeks). This is not only incredibly taxing on the poor girl, but you will have a lot of babies to find homes for.
  • If you definitely have only girls, then the next step is to wait 19 – 21 days, which is the gestation period of a mouse. If the 21 day mark passes, no babies for you!
  • However, if your mouse starts to look like she swallowed a golf ball (mice only start to show physical signs of pregnancy at about 2 weeks) you might soon have a litter on your hands.
  • Note, that many females will get pregnant at the pet shop so even if you do have only girls, you might still end up with a litter.

I want to breed my mice, what do I need to know?

Before you do anything, here’s a few things to think about:

  • What will you do with all the babies? Mice often have litters of 12 or 15, and can have 20 or more in some cases – can you keep them all, even the boys? Taking ‘surplus’ babies to a pet shop is far from ideal, as they may simply end up as someone’s dinner :(
  • What will you do if your pregnant mouse has a problem during delivery and needs vet attention? It’s a good idea to have both a trustworthy vet with small animal experience, and the necessary money on hand, should something happen.
  • Do you know the backgrounds of the mice you want to breed? Breeding pet shop mice which are likely riddled with cancer, immune deficiencies or temperament issues is a bad idea. Make sure you know that the mice you choose are from long-lived, healthy and well-tempered lines with pedigrees that go back at least 3 generations so you don’t get any nasty surprises. Knowing their genetic history will also help you plan for what colours and markings your babies will likely be.

If you’re still sure you want to breed your mice:

  • Female mice become fertile at approximately 5 weeks old, but that does NOT mean it’s a good idea to start breeding them at that tender age. The best age to breed a female is between 4 and 6 months old. Make sure she is fully mature and at her adult size before breeding her, or it could negatively affect her and her babies’ health and development. Any older than about 9 months is a risk, as older females that have not had a litter before often have fused hips that will make delivery dangerous or impossible.
  • You need a male and a female, obviously. If you only have a female, many breeders will be willing to stud out a male. This way, you can ask about his history before deciding. You’ll find less people interested in lending a female to breed with if you only have a male, so you may be better off buying a pedigreed female instead.
  • Always put the new couple into a clean cage. Females especially can be quite aggressive and territorial towards an interested male, and even if in a different cage, can often be forcefully protestant for the first few days. You’ll probably see him going after her a lot and her squeaking like crazy and running away. He probably won’t hurt her, but it can be a stressful time – for the mice, and for you!

How do I care for a pregnant mouse?

Housing

I recommend using a plastic tub or aquarium to raise babies in – or if you must use a cage with bars, make sure the bar spacing is 5mm or less. Babies, once they’re running around, are excellent escape artists! Also, try and make sure the cage is in a quiet area of the house where she won’t be disturbed too much.

Companions

You should separate a pregnant female mouse to raise the litter alone – living in a communal cage is stressful for mothers and companions may attack and kill the babies. I would especially do this if you have a group of 3 or more mice living together, as the situation could prove unpredictable, stressful and dangerous for mum and bubs. If you only have two mice, and they live together happily, separating the mum would leave two lonely girls and may not be necessary. The buddy will often act as a nanny, sharing the duties. If you choose to go this route, keep a close eye on the nanny when mum gives birth and make sure she’s not showing any aggression towards the babies.

Nesting

You will want to provide mum with plenty of nesting material and a nice safe, dark place to build her nest. I use non-scented, unbleached toilet paper for nesting, or you can also buy a sort of cotton wool designed for small animals from pet shops. Avoid using fabric (unless it’s felt), or anything with strings or threads that could twist around little baby feet or heads.

Feeding

Pregnant and nursing animals use a great deal of nutrients and energy creating, carrying and caring for little lives. They need a good quality, high protein diet, and lots of it. I tend to double the amount of food I give my pregnant girls, and add things like small bits of cooked chicken or tuna, scrambled egg, bread soaked in soy milk, porridge, baby food, etc. You could also add small animal vitamin drops to the water if you’d like to go the full hog, but I rarely do this as I feed a pretty good diet.

How do I care for and raise baby mice?

The most important thing to remember when you’ve got a litter is that mother knows best. You have almost no chance of successfully raising mouse babies under about 2 weeks old, and even from that age it’s extremely difficult. If you only remember one thing, remember this: Don’t stress, she knows what she’s doing!

Birth

You’ll notice when mum is getting close to giving birth that she’ll work furiously on her nest, and usually spend a lot of time in it. If you’re lucky enough to be present when she chooses to give birth, don’t touch her or the babies, poke around the nest, or disturb the cage at all – just leave her alone to do what she does best. Shortly after birth, you’ll start to hear the little squeaks of babies, which are called pinkies at this stage. They will squeak like this almost until they are weaned primarily for communication with their mother.

Cannibalism

Sometimes a mother mouse will kill and eat (or partially eat…) some of her babies. She may do this if the baby is malformed or not healthy, if she’s feeling stressed and nervous, if she’s unwell, or too old or young, or if she has a large litter and she feels she can’t raise them all. Usually any culls will happen at or close to birth, but it can also happen up until about 2 weeks. Occasionally you will get a mouse that just isn’t a very good mother and will kill or abandon her babies, but this is quite rare in my experience. In this situation, the best thing you can do is provide her with a stress-free environment. I would also avoid re-breeding any mouse who excessively culled.

Handling

If mum knows and trusts you, you can start to handle the babies from birth, but if she’s new or is a nervous mum, leave them 3 – 5 days, or more if she still exhibits stressful behaviour at that time. Start by gently stroking and moving the babies around in the nest, just to get your scent on them. See how mum reacts. If she’s fine, then the next day you can pick them up and cup them gently in your hands. Pinkies haven’t yet gained much control over their muscles, so they will spasm and pop all over the place. Be very careful not to drop them, and to only hold them inside the cage or over your lap so that if they do fall, they don’t fall far. If this does happen, don’t panic, pinkies (like human babies) usually bounce ;) It’s important to handle the bubs at least once a day, to make them nice and friendly. The more they’re used to being handled, the better pets they’ll make. I’ve found that the most vital time to handle them loads is the few days before and after they open their eyes – I think it impresses on them more if they see and feel you as the first thing they experience.

Development

At a few days old, babies that will be dark (agouti, black, etc) will start to develop pigment. At 8-10 days they will have velvety peach fuzz (from here they are called fuzzies), and now you should be able to sex them by checking for nipples under their arms along their sides. Their eyes will open at 12-14 days, and by 3 weeks they should be nibbling on solid food and hopping around the cage. At this stage they enter into what’s known as flea or popcorn stage. If you haven’t handled them much, or if their parents don’t have fantastic temperaments, they will pop out of your hand and leap everywhere. I often find that with enough handling, they pretty much skip this stage – but you will need to be careful taking them out of the cage anyway, just in case! At 4 weeks, it’s time to separate the boys and girls. This is VERY important! If you don’t, at about 5 weeks of age, mum and all your female babies will be pregnant! If you’re lucky, you’ve kept track of your boys and girls from your nipple-sexing, if not, you’ll need to sex by genitals at this stage because nipples are now hidden in fur.

Sexing baby mice

Sexing pinkies can be tricky, especially if you’ve never done it before. If you’re unsure and don’t want to make a mistake, wait until they’re 4 – 4.5 weeks old, and take them to a breeder, a vet or a reliable pet shop to sex for you. If you want to have a go yourself, here’s some tips.

You can actually sex baby mice from day 1, but I find about day 3 to be a good starting point. This is when the genitals become fat and easy to distinguish. When you turn them over, you will note a small pink protuberance, henceforth known as the pink bit. A girl’s pink bit is small and button-like, and sits quite close to the anus, connected by a small line. The boy’s pink bit is longer and has a wider, flatter end to it. It’s also further away from the anus and surrounded by slightly puffy flesh. Here are some pics, kindly provided by Coastal Rodents:

Female Pinky:
Female

Male Pinky:
Male

If you find this stage s bit tricky to work out, never fear – when they get enough fur to make them velvety, then the nipples become visible. Only female mice have nipples. They appear high under the arms and legs, and will look like little bald spots. I find this sexing method the easiest of all. If you have babies that are indistinguishable by markings, you could mark the tail of one sex with a non-toxic permanent marker at this point, to make it easier after their fur grows in.

Finally, between 4 and 5 weeks of age, the males’ testicles will start to drop. The best way to see this is by standing the mouse on your palm and pulling the tail gently down. Many people pull the tail up to see the genital area, but this often makes the boys defensively retract their testicles, and thus they’re very hard to see!

I have found a litter of orphaned wild mice, what do I do?

As far as I understand, it is extremely difficult to successfully raise baby mice (whether from a pet or wild mouse) if the babys’ eyes aren’t open yet. They require frequent feedings and stimulation to the point that you will get very little sleep. Even with that, the chances of them surviving are still low. If the eyes are open, they will still need nutrients via a milk supplement (the ones for puppies are quite good for them), but they should be beginning to eat solid food on their own and have a higher chance of survival.

I don’t have any experience with this personally, but here’s some handy sites:

Rat & Mouse Gazette: Caring for Orphaned Baby Rats or Mice
AFRMA: Caring for Orphans
The Fun Mouse: Caring for Orphaned Mice