Skip to Content

Do Rats Lay Eggs?

Some animals are incredibly successful at breeding. Rats are definitely one of those. 

And if you’ve seen some weird-looking balls that resemble eggs around the house, you might have thought that they are rat eggs. 

There is some confusion when it comes to the way rats reproduce. Some say that rats hatch, while others claim that rats give birth. Which one is it then; do rats lay eggs?

In this post, we’ll address some widespread misconceptions about rat “eggs”.

Do Rats Lay Eggs?

No, rats do not lay eggs. Contrary to what people believe, rats are mammals that give birth to live young. This is a characteristic of viviparous animals. 

There are two options for animals to bring their offspring into the world.

They will either lay eggs and have no physical connection with the baby (oviparity), or they will let the embryo (later fetus) develop inside them, and when the time is right, give birth to a live young (viviparity).

Rats are, as we just mentioned, viviparous.

Both styles of giving birth have some advantages, but also drawbacks. 

Advantages And Disadvantages Of Rats Laying Eggs

The main benefit of a rat hatching would be freedom and mobility; the mother would not be slowed down by having to carry lots of eggs in her belly. 

The biggest disadvantage of laying eggs would be the exposure of the rat’s eggs to some predators, weather, and other environmental changes. Letting the baby develop inside the reproductive tract, allows the rat mother to protect it until it’s ready to be born. 

Why Don’t Rats Lay Eggs?

Rats don’t lay eggs because it is more beneficial to them to give birth to live offspring. 

Millions of years ago, every animal laid eggs. Including human ancestors.

As time passed, animals slowly evolved and started giving birth to live babies because that was what helped them survive and get their species to the next generation. 

That was what most likely happened with rats. It was dangerous for rats to have their shell-covered offspring sitting out in the environment, so they adapted to keep their babies inside them for as long as possible. 

And one of evolution’s ways of getting to the next generation of rats was for them to give birth to live young.

How Do Rats Give Birth?

newborn baby rat
Newborn rat

Generally speaking, rats live to forage and mate. And they multiply at a terrifying speed – a female rat might give birth to anywhere from 8 to 18 pups per litter. Some tropical rats will have only one to six babies at once. 

Rats will breed throughout the year if conditions allow; the peak breeding seasons are summer and autumn.

Rats do not reproduce asexually; a male and a female rat will copulate for a brief period that only lasts for a fraction of a second. Some claim that female rats can mate around 500 times in six hours. 

Female rats can produce as many as 7 litters per year which means they can give over 120 offspring per year. 

The reproductive cycle of rats starts around the 2nd month of their life: male rats reach sexual maturity at about 6 to 10 weeks of age while females at 8 to 12 weeks.

After mating and conceiving, after 2 weeks pregnancy can be detected; the female rat will gain weight and her mammary (breast) will further develop. 

The average gestation time of a rat is 21 to 23 days and the baby rats are born deaf and blind.

Rat babies are called pups and weigh only 0.21 to 0.28 ounces at birth. 

21 days later, pups become weaned (they stop feeding on the mother’s milk and start eating other food). And in about 3 months, they are ready to reproduce. 

Most house rats, between 91 and 97% will die in their first year of life, according to the encyclopedia Walker’s Mammals of the World.

A female rat can quickly become pregnant after giving birth; however, it isn’t healthy for her to do it so fast again and take care of her pups at the same time.

Veterinarians advise giving your female rat pet at least 2 months between pregnancies for her to recover to full strength.

Egg-Laying Animals

According to the University of Georgia, over 99% of the world’s animals reproduce by laying eggs. That’s because most of the animals in the world are insects, and most insects hatch from eggs. 

Over 99% of mammals give live birth, including rats. Out of around 6,500 known mammal species, only 5 lay eggs.

These are the duck-billed platypus, short-beaked echidna, eastern long-beaked echidna, western long-beaked echidna, and Sir David’s long-beaked echidna. 

They are mammals that lay eggs and feed milk to their babies who are also known as puggles.

Most reptiles lay eggs. Out of approximately 11,000 known species of reptiles, over 80% lay eggs.

The only exceptions are some snakes and lizards that give live birth.

Most fish lay eggs. Out of around 34,000 known species of fish, less than 400 are livebearers.

This includes guppies, mollies, platies, swordtails, and some sharks. 

All species of birds lay eggs. This includes all of the 10,000 recognized species of birds.

Some ornithologists claim there are twice as many bird species, around 20,000.

Almost all amphibians lay eggs. Out of around 8,000 amphibian species, most will lay eggs in freshwater habitats.

There are only a few amphibian species that give live birth (several frog species).

Almost all insects reproduce by laying eggs. Out of 1 million known species of insects, of which 350,000 are beetles, all lay eggs.

The only exceptions are a beetle from Borneo, another from South America, and some aphids.

Final Thoughts – Do Rats Lay Eggs?

In conclusion, rats do not lay eggs. These long-tailed rodents reproduce viviparously and give birth to 8-18 babies in one litter. 

The main reason why rats do not lay eggs is evolution; giving birth to live young helped rats procreate and survive to this day.

Animals that hatch will have eggs that come in different forms! Some will have blue or white color, speckled patterns, and different textures, while others will be hard, soft, or even gooey. Animals may decide to lay them in the water, underground, or a nest. 

If you were pondering on the question “do rats lay eggs”, we hope this article removed all doubts.

And if you enjoyed it, here’s a recommendation on another popular read: do camels lay eggs or give birth to live young?

    Skip to content