This is weird and annoying!

[moosmom]

Suckling is a sign that the cat was taken from it's mother too early. My cat MooShoo used to suck on his own teats till he outgrew it. Picture it, I'm sound asleep in my bed and this "sucking" noise is coming from under the covers. It was a bit embarassing when I went to a cat show (when Moo was on the cat show circuit) and shared a room with some friends, who heard it.

[jennawing]

Suckling is a sign that the cat was taken from it's mother too early.

Being taken from their mother may be the cause of this behavior in some cats, but the real cause is due to their personality. Position in the household among other cats can also be a factor in how their personality developed when they were young- as well as the way they were introduced, how the introduction went off, etc. Most sucklers have an obsessive disposition in general- there will be many habits, toys, activities that they focus very strongly on. When you see a cat lay its ears back and close its eyes and keep on doing something they are being scolded not to do- it is a compulsion- a behavior that can be channeled into other activities, but not very likely eliminated. You can try to find him a new hobby- maybe a toy to obsess over instead- but he is always going to focus strongly on something to the point of irritating his humans.