How to determine ear type at day 2

When breeding a litter of mixed ear rats, it is possible to to determine which pups are dumbo and standard ear when they are around 2-3 days old.

The origin of the following photo is unknown as it was passed on to me, but i will replace it soon with my own photos:

Dumbo ears will lie flat against the head and are round in shape while the standard ears are folded to the front forming a small triangle. Once they ears open it is difficult to see which are dumbo and which are standard ear by looking at the ear type. It is then easier to look at the spacing between the ears (looking from either the top or back of head) or the shape of the ear. By the time they are 3 weeks old it should be easy to tell them apart.