When a female dog is in heat and is mounted by a male dog, it’s likely not play, but breeding. Unless both dogs are fixed, or one of them is fixed. Even fixed female has a scent of heat twice a year and male can sense it and mount her. So that is normal behavior – under these circumstances, it is very natural.
This behavior often appears initially at 4 months and older . It can be seen in both : male and female dogs. Sometimes neutering or spaying can decrease the frequency with which this behavior appears, but not always. Sometimes, even after altering a dog, this behavior continues to persist.
If the dog has a history of this behavior with no other reason – neutering or spaying will not solve the problem, because it is a learned behavior.
Some dogs hump other dogs, people, or household items because it gets them attention. Even if that attention is in negative, does not matter. The purpose of getting it is achieved, and the dog gets reprimanded.
Also, one of the possible reasons for that could possibly be irritation, inflammation, or simple infection in the genital area. This may be indicated especially for dogs who chew or lick at these areas excessively. If that is observed, then you need to check your dog with the vet for the potential problem.
Usually french bulldogs do not exhibit that problem very often. Determining a reason and underlying cause is a first step. The knowing the reason, you can move on to the next step- treatment. It can be quite a process, but at the end-very well worth it, you will be able to get rid of that behavior in your dog.