Well, you should never keep a live mouse in with a snake. It can do serious harm to a snake. Ever seen what mice can do to wood? Imagine the same damage on a snakes back.
That said. Make sure the tank is the right size (atleast a 20g long depending on the species of milk). Make sure there is a warm end (mid 80s) and a cool end. Hiding places at both warm and cool ends. Make sure the bedding is fresh and deep enough ( about 2 inches), always have clean water. Make sure the hiding spots are just big enough for the snake to fit in. Dont feed live (prekill), dont handle the snake for a few days before and after a meal. Feed at night, right before you go to bed and dont peak after you place the mouse in until morning. Make sure there are not bright lights on, and if you heat with lamps that they are shut off at night.
The snake seems to be really stressed, which kills thier feeding response.
Hope that helps,
Vinny
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“There is a grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that whilst this planet has gone on cycling according to the fixed laws of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.” -C. Darwin, 1859
Natural Selection Reptiles