toilet tries to drain more water than is in the bowl

my toilet flushes and drains but after the flapper drops the toilet seems to continue to drain. There is a gurgling type noise like it is sucking air. Any ideas?? Thanx

What are the other fixtures doing in the bathroom? i.e. Is the bathtub draining slow, sink draining slow, does the bathtub or sink gurgle like grasping for air?

More information is needed to help you.

THR

The tub was draining slowly until I removed a bit of my wifes hair from the drain but now it drains fine. No problems with the sink. I tried snaking the toilet and then went up on the roof and snaked again. We converted from septic to sewer last year and there is a pvc pipe in the back. It has a vent cap on top that says "DO NOT REMOVE" and a screw cap on the side of the pipe. I didn't know if I could take the screw cap off and try snaking from there. Just something tells me that this is some sort of partial clog. Its just my wife and I in the house and she says she did not put or drop anything in the toilet.  Thanx again