Just because if they say "eat", they use two different words.
"fressen" means: to eat (if the subject is an animal)
"essen" means: to eat (if the supject is a person)
"trinken" means: to drink (and the subject can be a person and an animal too)
Similar in Hungarian: An animal has "pofa" (animal's face), a person has "arc" (person's face), but for example both of them have "láb" (leg).