1. When a large cat feels unfamiliar with a kitten, it will treat the kitten as an enemy and bite it.
2. Manifestations of a dominant cat's controlling nature. When a dominant cat bites a kitten, it's asserting its alpha status and control.
3. Big cats are very territorial. When a kitten invades a big cat's territory, it will bite the kitten.
4. Adult cats are very jealous and don't want their owners to pamper the kittens, so they will attack the kittens.
5. A big cat biting a kitten could also be the kitten learning hunting skills, and the big cat might occasionally bite the kitten while playing.
6. If the two cats are of different sexes, the older cat may be in heat and is biting the younger female cat's neck to restrain her and ensure a smooth mating process. 
What behaviors between cats indicate friendliness?
1. They sniff each other's scent. Each cat has its own unique pheromones. When two cats get close, they will sniff each other's scent to determine if they are compatible.
2. Rubbing against each other's bodies. If two cats have a good relationship, they will rub against each other's bodies constantly as a way of comforting each other or expressing affection.
3. Cats sharing a litter box. If two cats get along very well, they will share a litter box and may even help each other bury their litter.
4. Expressing emotions through vocalizations. Cats express their feelings through vocalizations. If two cats are very close and familiar with each other, their vocalizations will tend to be affectionate and soft.
5. Grooming each other. In a cat's subconscious, only cats of higher status and greater power are qualified to lick other cats. Grooming each other is a sign of friendship.
