Psalm 104:21 (ESV)

21 The young lions roar for their prey, seeking their food from God.

As soon as it gets dark, the lions come out of their hiding place. They utter a stupendous roar to scare their prey. This is how they ask, as it were, the Lord to give them food.

''The element of eating and being eaten is in contrast with Genesis 1:1–31, where animals do not yet have to hunt for prey (Genesis 1:30), and Isaiah 11:6–7, where the lion lies peacefully beside the lamb. Psalm 104 connects totally to the present situation in creation and emphasizes that God still sustains his creation (see Psalm 104:27).''1

This eating and being eaten should not surprise us, because God himself has said after the flood that animals have also now been given to man for food (Genesis 9:3). In the same manner, to the meat-eating animals, God has given other animals for food (see Job 38:39–41).