On this page I hope to shed some light on the sometimes confusing subjecting of sexing rats. I say confusing because I remember when I first started keeping rats I was led to believe that sexing was very difficult to do, but really when you know what you are looking for it isn't. However do not underestimate the importance of correct sexing if you aren't sure get a second opinion from someone in the know other wise you could add to the large numbers of rats already needing homes.

So lets start with the basics a female rat is called a doe and a male rat is called a buck, this is similar to rabbits and mice, baby rats are called kittens in the U.K. and Pups in America (I'm not sure about other countries) or simply neonates (meaning newborns).

Dimorphic differences...

These are simply the differences you can observe in the rats without having to get hands on and turn him/her over, often these differences are only apparent after adolescence/ in adult rats and they are only a general rule as there is always bound to be some rats that don't fit with this norm.


Does tend to be smaller then bucks. Bucks are a lot chunkier and wider this I find especially noticeable between the ears and also the eyes. Some bucks also appear to have a slightly blunter nose with does' being generally much finer and pointier.


Although not very clear this photo shows the size difference between male (right) and female (left).



Bucks have much coarser/rougher fur with longer guard hairs (this maybe more noticeable in some varieties then others) the fur on bucks may also feel more greasy to touch.



Testicles will be evident in most adult bucks.

Temperament differences...

There are some marked differences in the temperament between does and bucks however again this may not be true for all individuals.


Bucks tend to be laid back some say lazy, they are more likely to sit still and be cuddled while you have them out and they are also more likely to scent mark (leave little droplets of urine) while out. Bucks can rarely have aggression problems towards other rats or even people when they reach adolescence .



Does are much more active and some are so busy they never keep still when out! They tend to only slow down as they get older or if they are ill etc They can be very reactive when they are in season.


Main anatomical differences...

This is where your going to have to flip your little girl/boy over and take a look at his/hers bits!

The above diagram shows the main genital differences in adult rats (For photos go to the bottom of the page).

These basic anatomical differences are apparent from birth to the trained eye and some breeders are able to take a fairly reliable stab at sexing their kittens at only a couple of days old however this does take practise. I will now talk through the main differences apparent in the above diagram:


Female has 6 pairs of nipples, these vary in their obviousness between individuals.


The distance between the urethra/vagina and anus is much shorter in the doe then the distance between the penis and anus in the castrated/ entire buck.


The Vagina is almost hidden under the urethra but will become more obvious when the doe is in season.



The adult entire buck has two large testicles.


In both the castrated and entire males the body is more pointed towards the tail, where as the doe can appear more rounded, this is also apparent from above.


Males have no obvious nipples.


Clearly the castrated male has no testicles present but as already mentioned the distance between the penis and the anus is still greater here then the vagina/urethra and anus in the doe.

Here are some real rat photos to complete the picture and hopefully reiterate what I have already said...


  The adult doe.                                                                               The adult buck.



I hope this helps with sexing your rats! - Em.

Last updated 26th August 2008

All photo's and some art work are produced by me, unless stated otherwise. Please do not take any of my art work or photos as allot of work has gone into them. If you do wish to use some of my art/gifs/photos then please email me for permission first.

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Disclaimer = I do not claim to be an authority on rodents or rats and any information on this page is just opinions and advice and is by no means a substitute for good books or veterinary advice.  All the toys on the toys page are just ideas and may not have been tried out so it is up to you to implement them and judge there safety.         




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