can the guy not separate them ???
It is very easy to tell the difference between male and female rats. Males have large,
prominent testicles which are visible under the tail from well before the age when they
are ready to leave their mother. They can draw their testicles up inside them if they are afraid,
but will not do this for a long period of time. A good rat breeder or staff at a good pet shop
will find it easy to tell which sex baby rats are. If they cannot tell the difference with ease,
they should not be selling the animals.
"They can draw their testicles up inside them if they are afraid"
wish I could do that
Sorry I couldnt be of more help