thats the bad part of feeding primarily one food item, and especially chicken (snakes seem to love chicken). the best advice i can give, is patience and consistency. ive normally never had a problem getting any of my snakes to convert to different prey items or to f/t. however, i have two of my holdbacks from a couple years ago, that i am having a horrible time getting off of rats and guiea pigs onto rabbits (and potentially other items). unfortuanetly, breeding season is upon us, so i am just stuffing them with whatever and whenever they will take. if and when they breed, i will rely on them going a little while without food, and will be hungry enough to eat whatever i offer, and then they will get on that. in the past, i have converted with the hunger method. just withhold food for like a month and half or two, then offer what you want to switch them too.
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retic is king of kings
1.0 Tiger Retic
1.0 Albino Tiger Retic
0.1 Striped Tiger Retic (het albino)
0.1 Salmon Boa
1.0 Albino Boa
0.1 False Water Cobra