Cats primarily howl, or yowl, as a form of communication during breeding season. Female cats express their receptivity toward male cats by yowling. Male cats attempt to secure a mate when they yowl. Some cats also yowl for human attention.
Cats that yowl for human attention are usually very young or very old. In such cases the yowling sometimes occurs at night when the cat's owner is asleep.
Some cats are more prone to yowling than others. Siamese cats are particularly known for being very vocal. Cats that have not been altered through spaying or neutering are also more likely to yowl than altered cats, according to the ASPCA.