On a bridge over one of the canals, they hid in the shadows and waited for dinner.

A few minutes later, a young couple strolled by. Each vampire grabbed one, sucked them dry and tossed the bodies into the canal below. 

They were extremely pleased with their meal and decided to have "secondi."

A few minutes later, another young couple approached and suffered the same fate as the first -- drained and tossed into the canal.

Our vampires, now fairly full, decided on dessert. In a short while a third young couple provided just that.

The vampires, full at last, started to walk away but stopped suddenly when they heard what sounded like crooning coming from under the bridge. 

They looked over the rail and saw an alligator feasting on the bodies and singing, only as an Italian alligator can,

"Drained Wops keep falling' on my head..."