When a rabbit's partner dies, the surviving rabbit can be dead within a day. Just from grief. The stress physically shuts its stomach down. Vets call it GI stasis, and it's a known killer of bonded partners. What you're watching might be the first hours of it. Rabbit vets actually encourage letting the survivor stay with the body. They tell owners to give the rabbit time with its partner, sniffing, nudging, lying next to her, sometimes for a few hours. Without that goodbye, the survivor can spend weeks searching the home for a partner who never comes back. With it, they're more likely to eat the next day. More likely to live. In 2008, researchers at the University of Edinburgh built an unusual cage to measure how much rabbits need each other. It had weighted doors at both ends. On one side, food. On the other, a few minutes of contact with another rabbit. The doors got heavier over time, so the rabbit had to really want it. The rabbits worked nearly as hard for the friend as they did for the food. Watch a bonded pair and you see why. They follow each other around all day. Sleep pressed together at night. Groom each other's face, head, and ears in long, careful sessions. When their partner is close they make a soft clicking sound with their teeth, called tooth purring. It sounds like a cat's purr. When one of them dies, the survivor's body reacts before its mind catches up. Rabbits are prey animals. Almost everything in the wild wants to eat them. Their bodies evolved one survival rule: when something scary happens, drop everything and run. So a rabbit's stress system is wired to switch hunger off in a crisis. Run first, eat later. That same wiring kicks in when a bonded mate suddenly disappears, except now there's nothing to run from. The rabbit hunches into itself, stops eating, and pulls away from everything around it. Some spend weeks searching the spot where their partner used to be. Rabbit welfare groups have documented cases of surviving partners who simply stopped eating after their mate died. They sometimes call it dying of heartbreak. The brown rabbit in the video is doing what a bonded rabbit does when his partner is suddenly gone. He stays close to her body. He keeps watch. He says goodbye the only way a rabbit can. If he survives the next two weeks, it will be because someone notices he has stopped eating and gets him to a vet who knows rabbits. If he doesn't, his stomach will give out before anything else does. A bonded rabbit's body is built around being with another rabbit. When that other rabbit is gone, the body itself starts to fall apart.