Sorry to hear. If I were you, I would start trapping and "doing away" with the rats. No food source=no snakes. That still seems strange though, as many copperheads and cottonmouths feed mostly on frogs, or at least from my experience that has held true. Maybe they are after the toads as well...
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Andy Maddox
AIM: SurfAndSkimTx04
MSN: Poloboy32486@hotmail.com
Yahoo:surfandskimtx04
Houston Herp Key
The Reptizone