Well here are some thoughts, not sure if any will help or not.
As for getting them on frozen, a good trick (IMO) is to do the following.
1st get them feeding on dangled rodents (i.e from tongs would be perfered, held by the tail. I personally dangle by hand but can be touchy).
Once you have them feeding readily off the tongs, you can try the stunned. After you get them on stunned you can get them on fresh killed. Lastly you can get them on frozen thawed. Some will let you skip steps, others may go backwards on you.
Another method would be to try a shoebox in the dark with the appropriate sized thawed in it. Leave the snake for up to 12 hours, dont disturb it to check, just let it sit.
As for switching from mice to rats, there is another benifit to tong feedings. You can try and switch things up when you start them on the tongs. Once it readily accepts off tongs, feed a small mouse, and try a small rat right after (dont go too big with either soo as to induce a regurge). Hopefully its hunger will overide its fear.
Once its on frozen, you can really push for rats then. You may even need to wash with handsoap your frozen (make sure to use a bio degradeable soap, and to rinse thoroughly) to get rid of the odor. If you do this with mice, try it also with the rat. If you get it used to thawed odorless lumps of rodent, it may no longer distinguish between mice and rats.
Lastly you may want to "starve" them for a few extra days between each step. Go 10 days rather then 5 or 7, and make them get enough of an appetite to again have the hunger overide the fear.
Just some tricks Ive picked up over the years. The rodent "washing" thing works well with problem feeding colubrids. However I havent yet had to try it with boids, so Im not sure if it works or not. But I can tell you I witnessed 40 corns that refused multiple live and frozen meals ALL eat first try with a washed pink rat, so it may work with other species as well.
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Mickey Hinkle
The Lizard King Reptiles
http://thelizardkingreptiles.com
402-614-6641
"I am the Lizard King, I can do anything" - Jim Morrison
