The Ratty Facts of Life: Sex Ed 101 for Randy Rats and Their Confused Owners


Q: What are the technical terms for male and female rats? For baby rats?

A: A male rat is called a “buck” and a female rat is called a “doe.” And, no, they don’t grow antlers as they age, that’s for jackalopes only. Baby rats are called kittens, pups or, fancifully, rittens (rat + kitten = ritten.) I prefer ratlettes when being silly myself. Newborn baby rats before they grow in hair are called pinkies (even though they look more like toes to me.) A group of baby rats is called a litter. A group of baby rats learning to eat mushy solid food is called disgusting and messy yet still strangely cute.


Q: Do female rats go into heat like female cats and dogs? What are the signs?

A: Yes, they do. The signs are hysterical. Females in heat will often wiggle their ears furiously and dart around the cage. If you scratch them on their backs, particularly by the base of their tails, they will hunker down, bottoms in the air, ears vibrating wildly. Flapping ears are the rat equivalent of fluttering eyelashes. Not all rats in heat will do this hilarious behavior, but many will. If your girl in heat lives with other females, sometimes they will mount each other during this period. It’s sort of the rat equivalent of those horrid “women in prison” movies. Just look away and try not to giggle too hard.


Q: How often does a female rat go into heat?
A: Every 5 days or so. However, placing a female not in heat with a male can make her go into season sooner. Big sexy boy rats can have that effect on the ladies. As can Barry White albums and soft candlelight.


Q: At what age do rats become fertile?
A: Rats can become pregnant at 6 weeks of age, which is why it’s a very good idea to separate them by gender by that time. Unlike with human beings, there is no stigma in the rat world against incest, so brothers and sisters can and will mate with one another if left together longer than 6 weeks.


Q: Is it true that female rats’ pelvic bones fuse at 7 months of age if they are not bred before then?
A: No, that’s a holdover from the world of guinea pig breeding but does not apply to rats. Breeding a female rat over the age of year for the first time can be problematic for other reasons. Just as human females are told that they can have trouble conceiving or delivering after a certain age, older female rats can have the same issues. Likewise, breeding a very young rat under 3 to 4 months of age can be problematic as she’s still growing and maturing.


Q: What is the best age to breed a female rat?
A: There are multiple schools of thought on this, but in my opinion from my own personal experience, I prefer to wait until the female is at least 4 months of age, provided she’s of good size and weight, and not to breed for the first time once the female is older than 10 to 12 months. For a second litter, up to 12 – 14 months seems to be safe. Again, this is from my experience and your mileage may vary.


Q: What is the best age to breed a male rat?
A: Not unlike human males (see Tony Randall), buck rats can produce offspring even into old age. Personally, I often like to wait until the buck is a year or so if I have any worries about health or temperament to see if anything unfortunate pops up. Also, though many males can be fertile long into old age, they do tend to be less fertile as they age, so breeding by the time they turn two or so is a good way to hedge your fertility bets.


Q: How many times should a female rat be bred in her lifetime?
A: I personally feel breeding a female more than three times is a bit taxing for her. I realize that, in the wild, they can and do have more litters than that, but I prefer to take no chances with my beloved ladies. In personal point of fact, I’ve never done more than two litters with a given doe but have known good responsible breeders to do up to three with no ill effects to the does’ health.


Q: How long between litters should I wait before breeding my doe for a second or third time?
A: Personally, I like to wait at least 6 weeks after the previous litter was weaned, which is usually by 5 weeks or so. However, you may want to wait longer depending on the state of your girl if she’s not as robust as she was pre-pregnancy. I have found that pregnancy and raising a litter tends to beef up my does a bit (my human mom friends concur with that assessment in themselves) so don’t be surprised if your slender young thing is a bit more robust post-babies.


Q: How many babies does the average litter contain?
A: The average rat litter size is between 8 and 12, though I’ve seen litters as large as 16 to 18 and as small as 1 or 2.


Q: Should I have my girl spayed? Are there any health benefits?
A: Anecdotal evidence suggests that spaying your females at 3 – 4 months of age can drastically reduce their chances of developing mammary tumors later in life. Do be certain your veterinarian is experienced with rat spays before having the operation performed.


Q: Should I have my boy neutered? Are there any health benefits?

A: There does not seem to be any real health advantage to neutering male rats. However, if you have a particularly aggressive male, neutering can work wonders as a hormonal attitude adjustment. In many cases, it also reduces the amount of urine marking that males do. Do be certain your veterinarian is experienced with rat neuters before having the operation performed. If you are planning to move the neutered lad in with unspayed females, wait at least 3 weeks post-surgery to be sure that all active sperm is gone so that your fellow doesn’t have a “last hurrah” with your ladies.


Q: When does my female rat hit menopause?
A: Generally, females are not fertile after 1.5 to 2 years of age. However, as with all females, ages of menopause can vary wildly, so I find it is very unwise to place an unspayed female of any age in with an unneutered male of any age unless you are quite prepared to deal with a late in life litter, which can be riskier than litters for younger females.


Q: What questions should I ask myself before deciding to breed or not to breed?

A: Some of the big questions you need to ask yourself are:
1: Do I know the health background of the intended parents well enough? Are these rats who are prone to tumors? Susceptible to myco inflammation? Pituitary tumors?
2: Do I have enough homes for all the babies? Given that the average litter size is 8 to 12 babies, it’s imperative that you have some homes lined up before you breed. There are a lot of rats languishing in shelters or being put to sleep or released into the wild where they die horribly, so be sure that you do not contribute to that sad trend.
3: Do I have enough funds set aside for food and vet care as needed? You will have multiple extra mouths to feed, not to mention vet bills should something go amiss with delivery.


Q: This is embarrassing to ask but, uh, what does rat mating look like?
A: The receptive female will hunker down with her hindquarters raised and the male will mount her from the rear and wiggle about furiously. Mating usually lasts only a few seconds with the female darting forward out from under the male. She will generally go a few steps then hunker down again to await the male’s mounting. Mating can occur many, many times in a session. The male will also often groom his genitals after a session of mating so as to, uh, freshen up before having another go at things. Hey, you asked. No, flowers and chocolates and dinner beforehand are generally not included in the process. Rats are just not known to be romantics, really.


Q: What is the mucous plug?
A: The mucous plug is, well, a little plug of mucous that forms in the female’s vaginal canal after the male deposits his sperm during mating. It’s not always visible with every successful mating, but it is distinctive looking (and gross) and perfectly healthy and normal.

Q: My female has some blood on her vaginal area post-mating. Is that normal?
A: A very small amount of blood is normal if the mating was prolonged or very vigorous. If the female is passing clots of blood, get her to the vet pronto as there is something wrong internally that needs vet care. This is true for does who were not mating – unlike humans, female rats do not menstruate so any bloody vaginal discharge is the sign of something wrong and should receive vet care ASAP!

Rat Breeding FAQ Index