AFRMA - Sexing 101

Sexing 101

A diagram of newborn male and female babies.
Baby Mice
Baby mice. The female on the left, the male on the right.	Baby mice with the female on the left, and the male on the right. Note the white patch on the female’s 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.	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.	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.	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 teats on the female at this age.	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.

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. 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.
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 bottom view of an adult female rat.	The side view of an adult female rat.

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Updated March 4, 2008.

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