In fact, if you search on Baidu for "differentiate hamsters from males and females", you can do it, there are pictures and it's easy to see

But nowadays, some of the females use paper to make their nests, so the ones that love to run around with paper in their mouths are the females

You can also turn the rat upside down and look at its belly to see if it has balls. >You can also turn the rat upside down and look at its belly, if it has balls, it's a male rat, if it doesn't, it's a female rat