They were vegetarian before the fall. After that as God removed His sustaining influence they began to be hostile to other creatures. When God finished His work of creation there was an idyllic, harmonious existence between earth, animals, and man. The world that we observe today is not very idyllic, and it is certainly not very harmonious. The fall of man brought this change about.
"And to every beast of the earth and every bird of the air and every creature that crawls upon the earth—everything that has the breath of life in it—I have given EVERY GREEN PLANT for food.” And it was so.
31And God looked upon all that He had made, and indeed, it was very good"
No death in paradise, so no carnivory (animals killing and eating animals) until Adam sinned and caused everything to begin to die. Then paradise was lost.