When do a Bichon’s ears droop?

Purebred Bichons are born with drooping, roundish ears, while non-purebreds may not droop until 3 to 7 months, a clear sign of purity. The drooped ears sit level with the top of the eyes and hide in the fluffy coat.

Also, purebred Bichons have naturally curly, soft, pleasant fur; straight, stiff coats likely mean not purebred.