AFRMA - Sexing 101 (sexing rats and mice)

Sexing 101

Baby Mice

2-day-old baby mice. The female on the left, the male on the right.

2-day-old baby mice with the female on the left, and the male on the right. Note the white patch in the middle–this is the stomach with milk in it.

6-day-old baby mice. The female on the left, the male on the right. You can see the teat marks starting to show up on the female.

16-day-old baby mice. The male on the left, the female on the right. You can see the teat marks on the female. Note the “line” from the anus to the urethra on the female. On males this area is furry.

16-day-old baby mice. The male on the left, the female on the right. The teat marks still show up on the female at this age.

Baby Rats

2-day-old baby rats. The female on the left, the male on the right.

2-day-old baby rats. The female on the left, the male on the right. You can see that they had just eaten and have full tummies (white patch). The black spots are their belly buttons.

7-day-old baby rats. The female on the left, the male on the right.

13-day-old baby rats. The male on the left, the female on the right. You can see the teat marks on the female at this age. The belly button spots still show.

13-day-old baby rats. The male on the left, the female on the right. You can see the teats on the female at this age. The belly button spots still show.

19-day-old baby rats. The female on the left, the male on the right. The male has small testicles showing at this age.

19-day-old baby rats. The female on the left, the male on the right. Note the “line” from the anus to the urethra on the female. On males this area is furry. The male has small testicles showing at this age.

Adult Mice

The side view of an adult male mouse.	The bottom view of an adult male mouse.
The side view of an adult female mouse.	The bottom view of an adult female mouse. The teats are clearly visible.

Adult Rats

Back view of young Seal Point Siamese rats. The female on the left, the male on the right.	Adult male rats “letting it all hang out.”
The side view of an adult male rat.	The bottom view of an adult male rat.
The side view of an adult female rat.	The bottom view of an adult female rat. You can see the vaginal opening just below the urethra.

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Updated May 8, 2012

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