NA map turtles, particularly the females, become particularly snail hungry as they reach maturity. They specialise in snail and shellfish eating in the wild, some females even develope oversized heads to cope with snails.
I'm not advocating you getting map turtles to cure your snail problems - they're very strong swimmers that thrive in currents as their natural habitats are rivers and ideally need huge tanks or pond setups, but its still interesting.
And I'll have as many snails as people will send me for my pair!