If we look for one man, who we might consider as the greatest in the funny animal genre, then I have little doubt the honorific would go to Carl Barks. Barks was a former Disney animator who took a moonlighting gig drawing half of a Donald Duck story in Dell Comics FOUR COLOR COMICS #9. Carl, who was unhappy with the working conditions at the studio, discovered that he had a great aptitude for comics.
Barks spent over 20 years anomalously producing work for Dell and Gold Key. Primarily he worked on Donald Duck or other characters in the “Donald Duck Universe” like Huey, Dewy & Louie, Grandma Duck and Gyro Gearloose. His most celebrated duck was one that he created, the miserly Uncle Scrooge.
However, Barks did not work exclusively on Disney properties. He also did a respectable run on the MGM animated characters Barney Bear and Benny the Burro. Here are a couple stories Barks did with them.
Reading this I am struck by the strange logic where the bear and the moose wear clothes and ol Benny stays naked!