What's a proper response to another dog attempting to mount your dog multiple times and the owner really not doing anything about it?
The owner kind of makes a weak attempt to seem like they're trying, but if I weren't there, they wouldn't intervene at all. I'm asking because I want to make sure that I don't over react next time.
Lot's of comments about dominance. This is an old erronous theory about dog behaviour based on a botched study. Dogs hump for many reasons, sexual is the obvious one, but also being nervous or poorly socialised.
What you should do is stop the behaviour, move your dog or theirs away and tell the owner to come get their dog.
If it happens in certain scenarios you can also stop it before the behaviour, so a common scenario is two dogs are playing, one dog gets overstimulated and then jumps on to hump, in that scenario you'd want to watch for earlier signs of overstimulation, wanting to stop, panting heavily, whale eyes, and stopping the play at that point.
My dog was a big tall greyhound, and one time he was humped by another dog - a tiny Yorkshire terrier. It was clinging to his hock (ankle) and banging away for dear life, while my dog ignored it. Its owner and I were both laughing too hard to do anything about it, it was a ludicrous sight.
If anything does something to your dog you don't agree with you are fully entitled to remove that thing from being near your dog. Grab the other dog by the collar and drag it away (not yanking, controlled movements).
If the owner of the other dog gets angry at this then state that you wouldn't have had to do so if they had the skills to keep their dog having good behaviour. Some times people need a verbal slap in the face to even start thinking about if they should do better. They won't agree with you in the situation, but it may help effect some change in their behaviour over time.
Either that or talk to other owners at the park about collectively shunning the problematic owner. It sounds harsh but I've seen this work and it's preferable to giving up a beloved community hangout just because of one asshole.
Would feel pretty horrifying if it were humans in the dog's place. I'd either tell the owner to get their dog to knock it off or find a new park with better trained dogs (and owners). :P
If at least one of them is fixed, at worst it's just a show of dominance. The bigger concern is for the dog humping. Those shows of dominance can lead to aggressive reactions from some dogs. If your dog isn't the type to react aggressively, it's not a big problem outside of any social awkwardness. The problem would be if that dog humped another that really didn't want it. Then there could be a fight. So it's in the owners best interest to discourage that behavior lest they hump the wrong dog.
All that said, even if your dog isn't the type to react and you just don't want another dog humping your dog, you should be fine taking some action. Either avoid the other dog or if that's not possible keep between your dog and the humper. Even physically holding the other dog away from yours should be fine. If the other owner takes offense to this, you can explain that you don't want their dog humping yours. At this point, they'll either concede and try to do better, remove their dog from the situation, or devolve into full Karen. Up to you how to handle that.
Ideally your dog should tell the other dog that it won't have it. Some times it takes longer than others for this to happen. For some dogs though this never happens
This is such a spot-on response. In addition to another in this thread (stating you are allowed to and should control the situation), it's 100% acceptable for a dog to correct another. Some dog owners see any "bad" interactions as aggressive but dogs can't learn to interact well without correcting each other. Unless it escalates into a legitimate fight, they should be allowed to work it out.
Hold their dog's collar and don't let go until the owner gets the hint. Just hold their dog in place. It's not hurting the animal but it's also not something the owner can just ignore.