Tolstoy has compared his characters to animals many times throughout War and Peace. Lise's upper lip is described as having a "squirrel-like expression" (Tolstoy 22), and Sonya is frequently alluded to as a kitten or cat. Though it could be argued Tolstoy gives these ridiculous descriptions to make characters more memorable, I would argue that Tolstoy truly sees humans as having characteristics of animals. Animals can also be seen as spontaneous and thoughtless at times (not to bash on animal rights activists), and Tolstoy seems to promote the belief that although humans are capable of complex thinking, we still have animal instincts. Don't get me wrong, we're not savage wild beasts all the time; however, in many of the war scenes in the novel, men are portrayed as making rash and savage decisions.
I did not make the connection between Tolstoy's portrayal of large groups of people and animals until Book Eleven when Tolstoy compares Moscow to a dying bee hive. He describes in great detail what the bees do in the dying hive, "languidly fighting, or cleaning themselves, or feeding one another" (Tolstoy 778), and then goes on to describe the men in Moscow doing the same. Many men are fighting for stupid reasons, and stealing food.
Tolstoy's parallel between animals and humans aligns with his belief in each individual's incomprehensible motives. As I have mentioned before, a major theme in War and Peace is irrational decisions such as Andrew's decision to marry Natasha based on her approaching her cousin before Mademoiselle Bourienne, or Pierre playing a game of patience to decide his future in the army. Tolstoy might explain these irrational decisions by the animal side of the human psyche. Humans and animals are all subject to innate desires that cannot be controlled. Although humans have advanced far enough to understand mathematics and plan wars, we still have internal desires similar to our furry friends.