|Female mouse pup - |
completely smooth underneath.
|Male pup - visible testicles.|
I was splitting cages Friday afternoon (separating pups from their parents, males pups in one cage and females in another cage). From the outward genitalia, some were easy to tell, some not so much. Then I realized: the females are completely flat underneath, while if you hold the males long enough and let them squirm a bit, their testicles bulge out. Bingo! Definitive sexing. And my supervisor will be quite happy that I got the right mice in the right cages, because if you don't, the males quickly impregnate the females.
It's the little things, right?!