what are the different in which the animals behave as the animals come to the barn?

The entrance and behavior of the animals telles us that there's already a certain hierarchy in place......

"At one end of the big barn, on a sort of raised platform, Major was already ensconced on his bed of straw, under a lantern which hung from a beam. He was twelve years old and had lately grown rather stout, but he was still a majestic-looking pig, with a wise and benevolent appearance in spite of the fact that his tuskes had never been cut. Before long the other animals began to arrive and make themselves comfortable after their different fashions. First came the three dogs, Bluebell, Jessie, and Pitcher, and then the pigs who settled down in the straw immediately in front of the platform. The hens perched themselves on the window-sills, the pigeons fluttered up to the rafters, the sheep and cows lay down behind the pigs and began to chew the cud. The two cart-horses, Boxer and Clover, came in together, walking very slowly and setting down their vast hairy hoofs with great care lest there should be some small animal concealed in the straw...."