How to tell male from female

1. The distance between the external genitalia and the anus is greater in males than in females at all postnatal stages.

2. For newborns, pick up by the tail.

3. For adults, put the mouse on the wire rack and grasp the tail of the mouse between the thumb and forefinger, and place the other fingers on the back and bend the butt end of the mouse up to you.