To unlock the animal actors you need to take peyote and become the animals.
(There are peyote location images and videos available online)
Once you've completed your peyote experience just select the animal from the casting trailer, to go into director mode, and the trophy will pop.
You only need one animal unlocked within this actor list for this trophy. However, as Kornfan2007 pointed out (in the comments), you will need to unlock all the animals for the hidden trophy in the Rockstar Editor trophy list.