In Animal Farm, in which ways do the animals behave like animals and how do the animals behave like humans?

The only animals that adopt human characteristics and behave as they do, are the pigs and to a certain extent Mollie, Moses the raven, the cat and Napoleon's guard dogs. The rest of the animals maintain their natural animal tendencies.

Mollie had been spoiled by Mr Jones and had been taught to become conceited. She had become used to wearing pretty ribbons and to eat sugar, habits which she was not prepared to sacrifice after the Rebellion. She was lazy and shirked doing even basic duties. She eventually ended up being owned by a publican so she could continue with her spoilt behaviour, a very human trait.

Moses repeatedly went around the farm to spread lies about Sugar Candy Mountain, an ideal place to which all animals would go to after death. He did not work and his lies had the support of the pigs since he was never punished for spreading them. This is a human quality, misleading and deceiving others for no particular reason, except for the pleasure to confuse. 

The cat became involved in teaching the birds but would often try to get them closer, for obvious reasons. She, just like Moses and Mollie, as well as Napoleon's dogs, hardly ever did any work and would disappear for long periods. Her deceptive and lazy nature make her more human.

Napoleon's guard dogs occupied a privileged position. Napoleon had secretly raised them since they were puppies and they had become loyal to him, acting on his brutal instructions, without question. They became tools of Napoleon's tyranny and kept the other animals in check, subjugating them to their master's authority. In this sense then, their assistance in the oppression of their fellow animals made them more human, since humans had been ruthlessly autocratic.

Of all the animals, the pigs, being the cleverest, had easily adopted human characteristics and quickly adopted their way of life. It started with them claiming privileges and denying these to other animals, such as their sole claim to the milk and windfall apples. Thereafter, they moved into the farmhouse and slept in beds. When murmurs were raised about their behaviour going against the principles of Animalism, they misled the animals, changed the commandments to suit them, and used propaganda to further confuse the others.

The pigs went even further, they started drinking alcohol, took to wearing human garments, walked on their hind legs and started carrying whips. Napoleon even took to smoking a pipe! The fact that they could read and write completes the cornucopia of human attributes that they possessed and exercised.

In the end, the pigs became so similar to the humans that it affected even their physical appearance. It became difficult for the other animals to distinguish between the two.

The creatures outside looked from pig to man, and from man to pig, and from pig to man again; but already it was impossible to say which was which.