I took a 10' Boa Constrictor off a resident's lawn here on Long Island. It was obviously released by a pet owner in the area but no one would take claim to the snake. It was difficult for us to get rid of the snake once we had it. Originally, I thought the Bronx Zoo would be happy to have it for their reptile/snake exhibit. But ... they said the snake was too common and ate too much.
It's not terribly unusual for residents here to have exotic pets that are either prohibited or those that grow so large that the owners just can't handle them anymore. Out of desperation, they often release them into the wild.