It's a bad idea, so I hope if you're doing it, you will quickly make alternative arrangements. All bearded dragons are thought to carry coccidia. Susan L., a veterinarian, pointed out that coccidia are protozoans and very annoying ones, at that. "Many animals have their own kind(s) and they cause diarrhea etc, and of course they are very contagious." I guess that's a good thing since virii are so much more difficult to treat. Thanks, Susan!
Coccidia is the biggy but you can also add that a uro's tail can easily put out an eye on a dragon. Beardies usually bite at the base of the tail when showing aggressive behavior. There are several other reasons too, like the basking temp ranges (bearides from 95 to 100°) with studies showing that 113° ambient air temps proving fatal to more than 50% of the adult test subjects in a 1 hour period, while others suffered neurological problems from over heating and had to be put down. As with most species, mixing lizards from different geographical locations is just asking for trouble!
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Gecko’s Mali Uromastyx Care Page v2.8