How did they react to their own animals singing beasts of england?
The beasts at the other farms started singing Beasts of England after receiving word of rebellion from Napoleon and Snowball. Pilkington and Frederick began to fear that their animals would also rebel.
You classify animals based on a number of things including: habitat location, time of sleep or rest, what they eat, how they eat, where they eat, what they do, what they look like, how they react with other animals of the same species, how they react with animals of a different species, and how they birth their young. All of these and many other factors contribute to how each animal is classified.