I read an interesting point somewhere out there that could help explain why Bearded Dragons seem to do okay with little or no UVB while Iguanas most definitely need it. Someone with a UVB meter in arizona observed his dragons in their permanent outdoor enclosure and noticed that they really only basked early morning and afternoon when the natural UVB was fairly low. Bearded Dragons in the wild also will eat small rodents which are a good source of calcium/D3. Because of this, Bearded Dragons may have developed the ability to use ingested D3 better than herbiverous lizards. Iguanas spend time in the sun during prime UVB producing periods and do not ingest foods that have a high amount of D3 naturally. They most likely evolved to get more D3 from the sun than many other lizards. Monitors eat fully developed vertebrates which contain good amounts of D3 explaining their ease of living with D3 only through dietary supplementation. Uromastyx are somewhere in between. I would assume a UVB bulb would be more important in Uromastyx than for Bearded Dragons but less important than for Iguanas. They do show a higher tolerance for heat than Bearded Dragons however so it is possible they bask during times of higher UVB intensity and therefore naturally get more D3 from the sun than BD's. They also eat a primarily herbiverous diet which contains very little D3. With the phonemonal growth Robyn is seeing in his Uromastyx due to their excellent setup and high temperatures (what are your nighttime temperatures Robyn? Are you doing a 24 hour heating schedule like you do with many Monitors?) I would be a little worried about poor bone density. Personally, I think diurnal lizards who do not naturally eat vertebrates should receive UVB to be in utmost health even though it has been shown that they can live their lives without it. Just my thoughts.



Peter

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