IDK if it works this way with dogs, but with cats, if one of your pets dies, you should show the body to the living relatives, let them sniff it and be aware of what's going on. They will deal with it better if they know what happened than if Other Buddy just disappeared one day and they don't know if buddy is coming back.

Animals can't express themselves vocally as we do, but I'm of the belief that they feel emotions and pain the same way we do. I mean why wouldn't they..

My cats absolutely have felt sad when another cat died.

When I lost my Chihuahua, my other dog and my roommates cats definitely acted a little off and we attributed it to them grieving. We also thought it could be them responding to our emotional state but we were never certain tbh

Definitely, our 2nd cat really changed when the first passed on. Much more quiet and really affectionate to us specifically.

Studies also find that cats will eat you face off if you die alone with them

my cat let out a loud and long meow of anger and disappointment each time i brought my dogs home at the beginning and he seemed to only tolerate their presence; he didn't seem to notice when they died. he's an asshole but i love him.

Garfield: “Now who will I push off the kitchen table?”