Unless you're a sponge, you and every multi-cellular animal on Earth have nerves…and many animals feel pain just like we do.
So when it comes to mice, rats, and rabbits grimacing in pain, we SHOULD be able to empathize as we feel pain too.
As animals that are mostly prey to predators, mice and rabbits (even horses) to tend to try and mask their pain. However, each has physical cues when something is amiss.
Loss of appetite, reluctance to move and general grumpiness are cues for minor pain like biting, kicking, and stomping are strong cues for severe pain.
The scientists believe that these studies can help improve science as a whole!