I'm not sure if anything has been published about their diets in the wild.

I suspect they eat lizards in the wild, but what kinds of lizards?

I know I tried feeding lizards to stubborn Eryx miliaris babies a few years back.

I tried:
hatchling Sceloporus - ignored
hatchling Hemidactylus - ignored
hatchling Green Anoles - ignored
hatchling Brown Anoles - ignored
hatchling Uta - ignored
small skinks - ignored
baby Texas Banded Geckos - gobbled up with much enthusiasm

So clearly this species seems to prefer Eublepharine geckos to anything else. Maybe muelleri are equally picky?

You could also try scenting pinkies/fuzzies with lizards. My experience is that given the right conditions, muelleri will eat domestic rodents. I've only owned 4 of them, but I've never seen one refuse live fuzzy mice.
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Chris Harrison
San Antonio, Texas