What Baby Mice Are Called

Whether you are breeding your own pet mice or are curious about the wildlife in your area, you may want to learn more about baby mice. Mice are highly social, highly intelligent, and very docile if raised from a young age. They make wonderful pets, and if you house a male pet mouse with a female pet mouse, you will have many more of these wonderful pets in almost no time. 

What are baby mice called? Baby mice are called either pups or pinkies. Female mice are called does, and male mice are called bucks. A group of mice is called either a horde or a “mischief.”

Mice are incredible animals – they are smart and social, can survive almost anywhere, and are just as happy in captivity as they are living in the wild. Read on if you would like to learn more about baby mice, including how they can reproduce so rapidly, how vulnerable they are at birth, and how they came to be called “pinkies”.

Why Are Baby Mice Called Pinkies?

All baby animals should have an adorable name associated with them, but there is actually more to the term “pinky” than a cute nickname. Mice have pink skin, and because they are born hairless, the name is fitting because of their coloring and lack of fur.

Baby mice are, literally, pink. Another reason this name is fitting is because there really is a resemblance between the newly born mouse and the tip of one’s pinky finger. All mice can be considered small in size, but baby mice are especially so – similar in both appearance and size to the tip of your smallest finger.

Baby Mice Fun Facts

Gestation and Pregnancy

You’ve likely heard that mice (or rather rodents, in general) are prolific breeders and produce offspring in record numbers. This is absolutely true, and for a few reasons:

• Mice reach sexual maturity early – a female mouse will reach sexual maturity in as little as 6 weeks from birth. A male mouse will reach sexual maturity by 8 weeks of age. Once a pup is born, the clock starts ticking before those babies can create families of their own.
• Mice have a short estrus cycle – the estrus cycle of a doe is only 4-5 days long, so she will go into heat once or twice a week for 15 hours at a time. Often there will be no outward sign that she is in heat, so it is almost impossible to know with accuracy when she is and is not fertile.
• Mice have a short gestation period – once pregnant, the doe will have only 19-21 days (three weeks or less) before she gives birth. It’s no wonder that her pups are born under-developed – after all, there is only so much time for fetal development in such a short amount of time.
• Mice can reproduce again almost immediately – after a doe gives birth, she will be fertile again in as little as 24 hours. When being bred back-to-back, pinkies will wean just as a new litter of siblings is arriving. 

If you consider these factors together, you can see that calling a mouse prolific is like calling the sun hot. It’s really kind of an understatement. The result of this prolificacy is a doe who is able to produce up to 15 litters per year or a new litter of 10-12 every three weeks. This would amount to up to 150-180 pinkies every year.

Negative Mouse Pregnancy Outcomes

There are, however, two situations that may affect the success of the pregnancy or the rearing of the pups. One is the Bruce Effect. This is a phenomenon where female rodents will lose an early pregnancy if exposed to the scent of an unfamiliar male.

If you suspect your doe may be pregnant, take care not to expose her to the scent (either from the animal himself around her or on your hands or clothing) of an unfamiliar male for the first five days after mating.

The second is the fact that it is not unheard of for a doe to eat part of her litter. It is thought that the most common cause of this cannibalistic behavior is, believe it or not, the protective instincts of the mother. If resources are scarce and a litter is too large to manage, the doe may eat the weakest pups to ensure the survival of the strongest babies.

Another cause may be stress or immaturity – young and first-time mothers are more likely to eat their babies than more experienced mothers. In addition to this unfortunate scenario, the studs present a danger as well if left in the enclosure at birth. Mature males are likely to kill and eat their offspring and should be removed from the doe before the arrival of the litter.

Baby Mice Are Born Under-Developed

Fetal development will vary across the animal kingdom, with some infants (humans, for example) born quite helpless and others (horses, for example) born running. Mice pups are on the more under-developed side of the spectrum, with the pinkies being completely helpless and vulnerable for their first couple of weeks.

• Mice are born without fur – pinkies are born just that – pink – without any fur on their hairless bodies. This leaves them vulnerable to exposure, and they must huddle with one another and with their mother to regulate their body temperature.
• Mice are born very small – pinkies are absolutely tiny – often weighing less than one gram. Not sure what to compare a gram to? A small metal paperclip weighs approximately one gram. So in terms of both weight and length, consider a small metal paperclip as comparable to a newborn pinkie.
• Mice are born blind – the nursery rhyme “Three Blind Mice” may have been inspired by a litter of pups. Mice are born completely blind, with their eyes sealed shut. Their eyes will not begin to open until around 13-14 days after birth.
• Mice are born deaf – as if being born blind and naked were not enough, pups are also born deaf. Their ears will not begin to open until around the 2-week mark.

Social Behavior of Baby Mice

With the singular exception of the deer mouse, mice, in general, are extremely social. A single mouse should never be kept alone, and in fact, it is recommended that pet owners keep at least three mice so that one is not left alone should his or her partner pass away (though we realize this will put one in the perpetual cycle of purchasing more and more mice to keep the number strong). While a mouse should never be kept alone, great care should be taken in the groupings that you keep together.

The social life of a mouse is so important that maintaining this structure has been shown to increase the likelihood a doe will successfully rear her pinkies upon birth. Keeping a pregnant doe with another pregnant doe (or a non-pregnant doe) will lower her levels of stress and will subsequently lower the chances that the doe will eat any of her offspring.

Another bonus of keeping pregnant females together is the fostering aspect – should a mother reject any of her offspring, another doe may take over the mothering duties. Do make sure to have a large enough enclosure in these scenarios – while does do seem to appreciate the company of others while pregnant and mothering, they don’t want to be on top of each other. 

As discussed earlier, mice reach sexual maturity at a very young age and do not discriminate when it comes to with whom they breed. Before your pinkies reach the ripe age of 6 weeks, you will need to separate them by sex.

If you are not sure how to sex a baby mouse, look at a tutorial online. Mice mature very quickly, and there should be visible differences in anatomy by the time they are 4-6 weeks of age. Female pinkies can stay with their mothers, and males will need to be moved to a separate enclosure.

While most females will get along well with female newcomers, males tend to do better with males they have known from an early age. If you would like to introduce a new male into the group, do so slowly and carefully, and keep a close eye on them until they are fully acclimated. 

Everything You Need To Know About Baby Mice

Mice are unique animals, both in the wild and in captivity. They grow and breed rapidly and are highly social and friendly. They make excellent pets due to their intelligent and docile natures while also becoming problematic as uninvited houseguests due to their prolific breeding.

If you have decided to breed your pet mice, it’s important to learn as much as you can about the pinkies you will be welcomed with after a few short weeks. Watching the miracle of life through the eyes of your pet is an experience you will not forget, and learning all you can about these tiny creatures will allow you to relax and enjoy it.