Charles H. Spurgeon on Psalms 104:21

The young lions roar. The roar of a lion, according to Burcheil, sometimes resembles the sound which is heard at the moment of an earthquake; and is produced by his laying his head on the ground, and uttering a half stifled growl, by which means the noise is conveyed along the earth. The instant it is heard by the animals reposing m the plains, they start up in alarm, fly in all directions, and even rush into the danger which they seek to avoid. From Cassell's Popular Natural History.