Some superheroes, such as Animal Man and Jungle Man, as well as superheroines such as Vixen and Wildcat, possessed powers mirroring those of animals. Various villains, such as Byth, Kung and the Changleings could even transform their bodies to replicate various animals.
On Earth-One, a bankrupt company known as Repli-Tech Industries had their entire board of directors made over as different types of animals using a DNA splicing technology developed by Doctor Lovecraft. Led by their CEO Rex Rogan, who had himself now became a man-lion, they decided to create a sporting venue known as the Arena wherein they would attract wealthy elite to fund their gladiatorial competitions. This drew the attention of the Justice League of America, who along with Rogan's girlfriend Irene who now opposed her ex's agenda. After battling the Ani-Men, the League determined that their adversaries were losing their humanity and left them on an island of the coast of Newfoundland as beasts to live out their lives.
On Earth-Two, Ivan Caroff along with his assistant Carl Carey had developed a radiation treatment that would transform those bathed in its lights into various animals. Seeking to fund his criminal schemes, Caroff's various minions attracted the attention of Starman who unleashed his inner ferocious feline when he was made into a lion, causing Caroff to himself mutate into a pig following the conclusion of their battle.