All you have to do is make them still and look at their private part and if there are 2 holes together then it's a girl and if there is a hole space then another hole then it's a boy =) hopefully that answer your question bye bye =)
Yes but its hard to hold them still enough to see. In a female the urethra (hole they wee from) and the vagina are right next to each other, in a male there is a visible gap. You may also be able to see the scrotum depending on the breed and age.
Here are pictures for you so you can compare what you see to the picture to help you better determine if your gerbil is male or female... www.gerbilbreeding.com
You wil no if it is a boy by looking AT HIM A COUP EL OF WEEKS LATER.,
Check at the pet store you bought it at
The pet shop sold me two girl gerbil's but my gray gerbil keep's and mounting the other one