It is very difficult to determine which predator killed the swan. The only way for sure is to have witnessed the attack. Usually, coyote or even something like a bobcat will go for the throat and strip the neck. Then, once the predator completes eating the carcass, other predators such as fox, raccoon, turtles, fish, etc., will also eat the carcass. So, we really can't tell just by looking at photos. The Regal Swan « Hide