Story time: the lady I got my big Blue gander from thought he killed his mate. She was going to put him down, but fortunately for the gander, the dogs who killed the goose were back the next night to finish off a large percentage of her flock.
That person was absolutely certain that dogs...
It's virtually unheard of for a gander to injure a goose. Are you absolutely certain that you didn't get some other predator inside your pen?
Could she have been spooked and run into the wire at full tilt and bruised her spine and cut her face?