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Baby Mice Growth Stages – How Fast do They Grow?

Before you start breeding fancy mice at home, it is important to learn more about the growth stages that mice go through. By doing so, you are going to better understand how to take care of them in every stage. It turns out that mice turn into adults rather quickly.

These little rodents are basically designed to reproduce in a rapid rate by nature. In this article, we are going to talk about their stages of growth. Then, we are going to answer some important questions about baby mouse care and why they grow so fast. Without further ado, let’s begin.

Week 1

In the first few days, what you are going to see is a bunch of naked little babies. They born with their eyes closed and it stays like that throughout the first week. It takes some time for their paws to develop as well, as they are rather webbed at first.

A newborn baby mouse does not have ears either. A couple small nubs are going to develop in the first couple of days that will continue to grow. A pet mouse that is a one and a half inch long is at least one week old. By the end of the week, their fur should start growing as well.

Week 2

During week two, you are going to see some colored fur growing. The ears of the juvenile mouse will be fully formed at this point as well. It is going to be towards the end of week two when you are going to see their eyes open. Fancy mice can’t see anything until they are around two weeks old.

This is when you are going to see most of the changes, as their lower and upper incisor teeth are going to grow rapidly. If the baby mouse is a female, its nipples are going to fully develop by the end of week two.

Week 3

Week three is when you can start feeding some solid foods to your juvenile mice. Before that, the only thing they should consume is breast milk from their mother. They are going to venture out from their nest and look for something to eat.

You can start feeding them wax worms, meal worms, cooked vegetables and soft fruits such as banana. In fact, there is a wide range of foods that you can feed them at this point. You can even buy mouse food at the pet store that is specifically made for mice that are very little.

Week 4

If you measure your mouse towards the end of the fourth week, it should be around two and a half inch long. This is when your fancy mouse has a body shape that actually makes him look like an adult. Mice that are four weeks old have fully developed teeth, ears, paws and fur as well.

At this point, their eyes should be completely clear and their nipples fully developed when it comes to females.

How Fast do Mouse Pups Grow?

Mouse pups grow incredibly fast, as they become sexually mature within the first 6 weeks of their lives. The changes they go through can be observed almost daily. If you spend a lot of time with your pet mice, you can witness as their eyes open and as their fur and teeth start to grow.

Before you know it, you are going to have a mouse with fully grown fur, big ears and large frontal teeth. Mice are designed to grow up really fast in order to be able to reproduce as soon as possible. After all, this is how they maintain their species out in the wild where the conditions are harsh.

They are constantly moving, looking for resources and opportunities to build nests and reproduce. Their survival skills are insane and they can survive during the winter as well. It takes only six days for a pet mouse baby to grow some fur and start making squeaking noises.

When Can I Touch Baby Mice?

Out in the wild, mouse mothers value their own lives more than of their babies. After all, they can breed again shortly after. If you bother baby mice too much and too early, you are only going to increase the risk of infanticide. Sometimes, mice have no other choice but to consider us as predators.

We are big, strong and they don’t know for sure whether we pose a threat to them or not. When we touch their babies and try to pick them up, they consider it as a potential threat. Although this is instinctive, it really depends on how accustomed the mouse is to you.

For every next litter she gives birth to, the chances of her killing them are going to be lower and lower. At the first stage when pet mouse babies are naked and helpless, there is really no point in picking them up. The first time it is going to be safe to pick them up is when they are about two weeks old.

At that stage, mice have well-established fur and you are most likely not going to harm them. On the other hand, their mother is going to be more indulgent about it as well. Nevertheless, don’t be surprised if those juvenile mice are afraid of you.

They might try to jump or run out of your hand when you handle them. Be careful because they can hurt themselves if they fall down.

What do Baby Mice Eat?

The baby mouse diet ideally consists of the milk that their mother provides. They are not able to eat anything solid until they are 3 to 4 weeks old. That is when you can feed them some mouse food soaked in water so that it is easier for them to eat.

Mealworms and waxworms can also be among their first foods to eat. For baby mice, it is not so much of a problem to eat something with high fat content. They are still growing so those foods are not as harmful for them as for adult mice.

Feeding them some crushed up nuts is not a bad idea either. Besides, there are foods specifically made for pet mouse babies that you can buy at the pet store.

When do Mice Become Mature?

It does not take much time for mice to become mature. It takes about 6 weeks, which is only one and a half month to become sexually mature. Then, you can already start thinking about separating them for each other in order to prevent them from reproducing again.

You can only imagine how many mice can be born in the span of a single year if every one of them is ready to reproduce after 6 weeks. Let’s say that a single mouse gives birth to 6-8 litter. Given that they all manage to survive, all of those babies can grow up and reproduce.

If this would happen on repeat throughout a year, you would end up with close to a million mice. It is such a huge number that it’s hard to even imagine. Moreover, keeping mice as pets also means that they can breed more.

Out in nature, it is very unlikely for mouse babies to stay alive during the winter months.

How Long do Pet Mice Live?

The numbers are interesting when we compare wild mice and fancy mice in terms of life span. It turns out that pet mice can live for as long as 2-3 years in a cage. Wild mice, on the other hand, only live for 12 months tops because of the harsh conditions around them.

This is understandable if you consider how convenient it actually is for mice to have a caretaker. Fancy mice are not exposed to wild temperature fluctuations and are typically well-fed with healthy foods. They also live in a much cleaner environment where the risk of disease is minimal.

Not to mention that by installing tubes, running wheels and giving other toys to your mouse, he will exercise a lot. It is a healthy lifestyle that keeps his energy levels up the whole time. Wild mice often can’t establish healthy sleeping habits either because of the lack of comfort.

Wrapping Up

Baby mice grow up so fast that the whole process can be followed on a day-to-day basis. Meanwhile, all they need is some breast milk from their mom and they are going to thrive. You will be able to observe how their ears grow out and how the web disappears from their paws.

If you are wondering when you can start to give them food, the rule of thumb is to wait until their eyes open. Until then, they rely on smelling and touching, which helps them find their mother’s breasts. Make sure to clean up the cage before the female mouse gives birth.

From then on, you don’t really need to do anything for a week. Pet mice are outstanding parents, especially when they are not bothered. They take care of their babies and always make sure they are well-fed.

avatar I’m Peter King, writer and editor of this blog. I’m a lifelong animal advocate and volunteer at the Animal Rescue League. On this blog I help people learn about pet mice. As a responsible pet owner, you should learn about your pet’s need before getting it. If you have any question or need help, please leave your comment below.

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