How does Steinbeck convey Lennie's animal like qualities?

Steinback compares Lennie to a bear saying by saying "he walked heavily, dragging his feet a little, the way a bear drags his paws." The way Lennie snorts into the water while drinking is compared to a horse and when Lennie finds another mouse and George demands he give it back, Steinback writes that "Slowly, like a terrier who doesn't want to bring a ball to his master, Lennie approached".