non of my milks are house broken, but oddly enough i do have a few other species that seem to be.

both of my grease kings always soil the same corner of their cage... the coner behind their water bowl that is pushed into the corner.

my female argentine boa always goes along the back wall of her boaphile.. right up against the wall.

i had a corn snake that would only go in it's water bowl. after about 6 months i found a nice new owner thanks to craigslist.
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1.1 Argentine Boas
1.1 Dumerils Boas
1.1 Black Milk Snakes
2.3 California King Snakes
1.1 Nelsons Milk Snakes
2.2 Corn Snakes