The reasons why a cat bites another cat's neck:
1. Biting the neck is a relatively common phenomenon. It may be fighting or playing, and it is usually a light bite. Will not cause serious harm.
2. If the old cat bites the kitten's neck, it may be that the old cat is accepting the kitten and treats the kitten as a child.
3. It may be mating. If the male cat is riding on the female cat and biting her neck, it is probably because the two cats are mating.
Things to note after a cat is bitten on the neck:

1. Check whether there is a wound on the cat’s neck. If so, perform anti-inflammatory and sterilization treatment in time.

2. Check whether the cat bites or is bitten on the neck because it is in heat. If the cat is in heat, you can take it to a pet hospital for sterilization surgery.

3. If the neck biting is caused by a fight, it should be stopped in time and the cat should be isolated and educated.