Baby Rat Development

This is merely a guide for those interested in how their baby has grown or for those curious about a babies development. I do NOT encourage breeding in any way without alot of research & preperation beforehand. It is not something to get into lightly!

The rat's gestation period is 19 to 23 days. 21 days is average.
Baby rats are called Kittens or sometimes the cute name Rittens (combing the name Rat + Kitten), sometimes they are also called pups.
Average litter size is between 8-12 babies though they can much have more! I have heard of litters up to 28! Dwarfs often have smaller litters of 3-5

This guide is based on an average time frame but each baby is unique and may develop at different rates. Some faster, some slower.

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Rats average lifespan is 2-3 years.

Rats reach fully grown between 6-8 months old.

They can be sexually mature at 5-6 weeks old. But it is very important for females to mature both physically and mentally before being mated, which is 5-6 months. Females do not go through menopause, fertility can wane but there is no specific age and rats over 2 years old have still been known to give birth. Older rats giving birth can come with many risks and complications.

Males may go through a hormonal period at around 6+ months old.


Rats can actually differ in size by quite a bit. Just like humans have different heights, weights and body shapes. You can have very large rats or quite petite.

In general female adult rats weigh between 300-450g and adult males weigh between 450-650g.

And adult dwarfs are around 80-115g some lines up to 120g. It is important to note that dwarf is a specific gene and not just smaller rats.

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