>>Difficult? I've heard yes and no from a couple different people I talked to.
Yes... and no!
>>I'm thinking of getting 1.1 melanistic yearling easterns, but they only eat toads and frogs. The person I am getting them from said it would be easy to get them on mice, true?
A lot of your success depends upon the personality of the snake, and your available resources
>>How exactly should I go about getting them on mice?
As you can imagine there are an infinite amount of ways. I personally do not believe in feeding amphibians to hognoses, and I have successfully switched Easterns over to mice on numerous occasions without sacrificing a single frog. Ideally, you would set up a toad just as if it were a pet and keep it well fed and trained to eat off the end of hemostats. The reason I say that, is because the BEST source of scent I have come across is the saliva of frogs. Almost any native species of frog will work as well. I have had a collection of toads to choose from when doing this, but basically all of them were habituated to hand feeding and would readily snap at a pinky. If you weren't paying enough attention, they will even pull the pinky out of the hemostats and swallow it. The idea here is to let them get a hold of it and fight with it for a few seconds, all the while getting their saliva all over it, and pull it back out and immediately offer it to the snake. Some of the other advantages to keeping the toad in captivity is to catch it while it is in mid-shed, and you can snatch the skin and freeze it for later use. All it takes is a piece of toad skin half the size of a dime. Those are some of my favored techniques, and the link below will provide you with more. As of late, scenting with tuna fish seems to be a novel but successful method.
http://forum.kingsnake.com/hognose/messages/5710.html
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"I know the human being and fish can coexist peacefully."
Governor George W. Bush, Jr.
"Sometimes I think the surest sign that intelligent life exists elsewhere in the universe is that none of it has tried to contact us."
Calvin and Hobbes (Scientific Progress Goes 'Boink', 1991)