New puppy is well behaved, except…

Hey everyone! I’ll start by saying I’m a huge dog person. I grew up with dogs, raised a few puppies, and have put in a lot of work with them over the years.

For some background, my partner and I have been living together for a few years, and last year my mom moved into our basement (not a separate suite, just a room and living room downstairs) and yesterday, she got a puppy

Kilo is 4 months old, and he’s very very precious, he’s a Catahoula leopard dog mixed with (what I assume) is a lab. We also take care of my grandmas dog Pepé (French bulldog) as my grandmas not physically well lately, and he’s totally fine with her, if not a bit obnoxious trying to constantly play, but he’s a puppy so it’s expected.

Now onto the strange behaviour. Intro from his previous owner to my mom and I went very well, extremely well behaved, knows sit and lay down already, and had never been on a leash until we took him and he was a DREAM to leash train. He also has a food obsession but that’s common in labs and a behaviour that we’ve trained out of previous dogs we’ve had. Anyways, my partner gets home from work most days at around 7:30-8:00 PM so he’s not around much except for the weekends, and Kilo does NOT vibe with him at all.

Kilo barks incessantly, and has even snapped at him a few times during introductions. I think he’s resource guarding my mom, who he IMMEDIATELY has extreme separation anxiety with. It’s been one day and he follows her everywhere, barks and whines when she leaves, and will not listen when she’s not around, yet when she’s around he’s the perfect puppy. It’s ONLY at my partner, not at strangers or other dogs on walks at all, and not at me at all.

I’m not sure if it’s because my partner has a big beard, or is more masculine. It’d be weird if it was a man thing, cause even tho I’m biologically male (they/them pronouns) he doesn’t bark or have any issue with me at all. I know that Kilo had previous experiences with an owner who was an addict and almost homeless, so maybe someone with a beard affected him negatively? The previous owners brother in law (who gave us the dog) said this is completely out of character and new for him, and he’s never even heard him bark for a long period of time like he does with my partner.

What do I do to help train him out of this behaviour? He’s young and mouldable, but I have a huge gathering on Thursday of people, so we’ll see if it’s a people thing or just a my partner thing. Regardless, I want to work on this as it’s also sad and debilitating for my partner who’s never owned a dog and was so excited to meet him.

Help!