My dog keeps trying to bite my other dog's neck

I'd also add that my girls regularly grab each other by the face and throat when they're playing.

It's actually very gentle, even if it comes with some awful growling. I'd even say "delicate" in terms of how they handle each other.

Mia also loves grabbing Naïs by one of her back legs. She doesn't squeeze — she just holds it in her mouth. Then she pretends to chew on it, and when her sister retaliates, they launch themselves at each other's faces, often while lying on their backs. Very, very chilled. It's just play.

How old is Princesse?

Has Sultan spent enough time around adult dogs for them to have taught him bite inhibition?

You should let them play – under supervision – provided Sultan has been properly socialised by other dogs.

Puppies mouth things a lot... I don't see anything to worry about here. If he's doing it with other dogs, he'll learn from them... whether they're play-fighting or just having a run around. He'll also get the hang of bite inhibition; some dogs that aren't as well-socialised still mouth when they're older or don't know how to control their jaw strength, which can cause problems later on because as a puppy gets bigger, the corrections from other dogs will get a lot firmer...

When ours was a pup, she used to mouth everything—her friends' legs, ears, jowls, necks... We'd tell her "leave it" if she was being too persistent or shaking her head too much... that was our cue. After a couple of seconds, once she'd let go and calmed down a bit, she'd start playing again... or just go straight back to running around once she'd let go...

As for mouthing humans, definitely don't let him get away with that.

Same here. Dogs very often play by grabbing each other by the throat. I’ve got a good example: my two-and-a-half-year-old dog has become real best mates with a female puppy in my village. While she was little, he played "gently" with her. Nowadays, this Labrador cross is 9 or 10 months old and she’s the same size as my lad. When she walks past our house with her owner, we often let them into the garden so they can have a safe play. Now, they have these endless play sessions where they grab each other by the throat and pin their "enemy" to the ground. It looks like they’re about to rip each other’s throats out, but that’s not the case at all! It’s all very controlled; there’s no yelping or whimpering. Both of them know exactly how to gauge the strength of their jaws. Of course, you still need to stay vigilant so you can step in if things get out of hand!

Wild animals all play this way (lion cubs, wolf cubs, fox cubs, etc.). It’s like practice for their future lives...

Keep an eye on your two dogs, but don't panic if the puppy grabs your female by the throat. As long as there are no signs of aggression between them, it's just an invitation to play.

I think it’s just play. My dog does the same with other dogs—I call it inviting them to play—and then she often does it during the game itself. She even grabs the other dog by the throat sometimes, but she doesn’t bite down and has perfect bite inhibition; it’s just her way of playing. On top of that, mine makes little grunts of pleasure, which can be a bit scary if you’re not used to it. You shouldn't be afraid or panic, as that might just wind the dog up; if you see things getting a bit too heated, you can stop them for a moment to let them calm down. But honestly, if he’s a lovely dog with other dogs as well as people and knows his doggy social cues, there’s no issue. Just keep an eye on it to make sure it doesn't go too far, but a dog putting its mouth on another’s neck is perfectly normal.

For example, in this video of Nouchka and Olly, you can clearly see that the aim of the game is to grab each other by the throat or neck, but it doesn't cause any injuries:

https://www.youtube.com/watch?v=RZC8rCKg3Lk