Baby Mouse vs Baby Rat: What’s the Difference?

Written by August Croft
Updated: September 24, 2023
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Upon first glance, you may not be able to tell the difference between a baby mousevs baby rat. But there are some key differences between these two rodents, whether it is evident by looking at them or not. For example, mice and rats are both from the Muridae family, but this does not mean that they are the same creature.

In this article, we will go over some of the key differences between baby rats and baby mice, including their appearance, lifespan, gestation period, and more. If you’ve always wanted to be able to tell the difference between a baby mousef and a baby rat, you’re in the right place! Let’s dive in.

Comparing a Baby Mouse vs Baby Rat

Baby rates are significantly larger than baby mice.
Baby MouseBaby Rat
Size ½ inch to one inch long2-5 inches long
Weight 1-3 grams5-8 grams
Lifespan 1-2 years2-5 years
Tail Same length as body and headShorter than body
Gestation 10-20 days15-25 days
Appearance Born hairless and pinkBorn pink, hairless, with large heads

The Main Differences Between a Baby Mouse vs Baby Rat

Baby mouse vs baby rat

Both baby mice and rats are born blind, without fur, and a bright pink color, but the body of a baby mouse is much more uniform than the body of a baby rat.

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There are a few key differences between a baby mouse vs baby rat. Both baby mice and rats are born blind, without fur, and a bright pink color, but the body of a baby mouse is much more uniform than the body of a baby rat. Baby rats are also born with extremely short tails, while baby mice have longer tails than mice throughout their life.

But there are even more differences between these two rodents. Let’s talk more about them now.

Baby Mouse vs Baby Rat: Appearance

A key difference between a baby mouse vs baby rat is their appearance. At birth, a baby mouse looks very similar to a baby rat, but there are some key differences to look for. For example, a baby mouse will have a body that is more uniform in shape, while a baby rat will have a much larger head in proportion to the rest of its body.

As baby mice and rats grow, the appearance between these two rodents will continue to change and shift. Rats are often found in a variety of different colors, including those with splotches, while baby mice are more likely to be found in one uniform color. Baby mice will also have much larger ears than baby rats.

Baby mouse vs baby rat

Rats are often found in a variety of different colors, including those with splotches, while baby mice are more likely to be found in one uniform color.

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Baby Mouse vs Baby Rat: Tail

Another key difference between baby mice and baby rats can be found in their tails. Baby rats are born with short tails and these tails remain smaller than the overall length of their bodies; baby mice are born with long tails and they keep these long tails throughout their lives. Mice tails are at least as long as their bodies, if not often double the length.

It is important to note that rat tails are also much thicker than mice tails, though this may not be evident when a baby rat is firstborn. However, as these rodents age, you will soon be able to tell the difference between them based on their tails alone.

Baby Mouse vs Baby Rat: Size

A major difference between baby mice vs baby rats is their overall size. Baby rats average 2-4 inches from birth to juvenile age, while baby mice range from 1-3 inches during this same period. Rats are also much larger in appearance when compared to mice, even after first being born. Baby mice are slender and more evenly shaped, while baby rats tend to have larger frames and heads.

The differences between baby mice and baby rats will only continue to become more apparent as they age. The sizes will continue to grow further apart, with most rats growing to almost triple the size of the average mouse.

Baby rats average 2-4 inches from birth to juvenile age, while baby mice range from 1-3 inches during this same period.

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Baby Mouse vs Baby Rat: Gestation Period

Another difference between baby mice vs baby rats is their gestation period. While these rodents are from the same genetic family, this does not make them identical from birth. Baby mice average anywhere from 10-20 days in the womb, while baby rats need an average of 20-30 days in the womb.

The size of these rodents may play some part in the overall gestation period for baby mice vs baby rats. Either way, both rats and mice breed throughout the year, during any season. Female mice and rats can get pregnant immediately after giving birth as well, which means the average female rodent can birth dozens of litters per year!

Baby Mouse - Baby Mice

Baby rats are born with short tails and these tails remain smaller than the overall length of their bodies; baby mice are born with long tails and they keep these long tails throughout their lives.

©RICHARD-ASQUITH/Shutterstock.com

Baby Mouse vs Baby Rat: Lifespan

A final key difference between a baby mouse and a baby rat can be found in the rodent’s overall lifespan. While you won’t know it at the time of them being born, a baby mouse lives a shorter life overall than a baby rat. Most mice live an average of 1-2 years, both in captivity and in the wild, while most rats live 2-3 years in the wild and an average of 5 years in captivity.

While a baby mouse may share many similarities to a baby rat, mice tend to find themselves caught in mouse traps far more often than rats do, and their overall size gives them a shorter lifespan genetically. However, both mice and rats can live long and healthy lives if kept as captive pets, but rats consistently live longer in both locations, regardless of quality of life.

What Does it Mean if You Find a Baby Mouse in Your House?

baby mouse siblings

Baby mice are no longer than 2 inches in length.

©iStock.com/Kseniia Glazkova

You can tell the differences between a baby mouse and a baby rat by considering their size and fur color. Baby mice are usually around 1 to 2 inches long, whereas baby rats measure around 2 to 4 inches.

In terms of fur color, baby mice usually have gray or brown fur, while baby rats tend to have brown or black fur.

Additionally, finding a baby mouse or rat in your house is never a good sign.

While baby mice may seem cute and innocent, they can serve as an early warning sign of a mouse infestation in your home. The presence of one baby mouse often indicates the existence of a litter, which means there are usually a few adults lingering around as well.

It’s important to search for other signs of mice such as droppings and to call a professional if necessary.

The photo featured at the top of this post is © Maslov Dmitry/Shutterstock.com


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About the Author

August Croft is a writer at A-Z Animals where their primary focus is on astrology, symbolism, and gardening. August has been writing a variety of content for over 4 years and holds a Bachelor of Fine Arts Degree in Theater from Southern Oregon University, which they earned in 2014. They are currently working toward a professional certification in astrology and chart reading. A resident of Oregon, August enjoys playwriting, craft beer, and cooking seasonal recipes for their friends and high school sweetheart.

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