When my first bunny died, I didn’t know to leave the body with the mates, and they looked for him for a week or so (can’t remember how long exactly)
I later asked my vet what bunnies normally do when they see the body of their mate, and she said some bunnies will know right away and won’t go near the body. Other will lie by the body, try and groom etc, but then will eventually move away and lie down somewhere else and not return to the body and that’s when we think they have figured out what is going on.
I can tell you from personal experience with Jack that it was important for him have the body — Details of how Jack realized she was gone are a bit sad so if you don’t want to read the next part then skip to the next post.
Jack and Rucy’s story:
Jack definitely knew when Rucy’s body was just her body after she passed. He also had been with her right before she passed (at home) so I’m not sure if that makes a difference or not. Anyway, minutes after she died, I set her down on the floor where they normally would lie together. He went over and began trying groom her, but I could tell he knew something was different, because he would groom her, then sniff her in a strange way–sort of burying his nose deeper in her fur, then actually tried to mount her, but before he even really started he suddenly stopped, looked down at her, licked her eye, backed up partially off of her, sniffed her in that weird way again, stared for a moment, and then slowly got off of her and hung out on the other side of the room. I left her there for an hour, but he didn’t go near her.
He was one very sad bunny for a couple of weeks, and every once in awhile he would look up (get up on his hind legs) to see the higher areas she liked to hang out on (I wonder if her scent still lingered there and he’d catch it every once in awhile), but he never went really searching for her. So even though he accepted the fact she was gone…for him, he had to go through a mourning time. (not all bunnies do, some bounce back very quickly). But I think for Jack, it was helpful because I really believe he would have looked and looked for her and it would have dragged on. Right now, if Vivian chooses to leave the bunny room and go to her secret hidout in the house, he will look for her off and on until she returns — so I know that is part of his personality.)