Most reptiles require UV-B light exposure for vitamin D synthesis and calcium metabolism. The failure to provide adequate UV-B is a widespread but preventable welfare crisis in captive reptiles.
Metabolic bone disease from inadequate UV-B provision is a welfare catastrophe in slow motion. The process of developing MBD takes months - during which the reptile is silently losing bone density and calcium regulation before visible signs appear. By the time fractures or obvious deformity are apparent, significant suffering has been occurring. The ubiquity of this condition in pet reptiles reflects both inadequate keeper education and the failure of the pet trade to properly inform purchasers of species' requirements. Reptiles that cannot express pain responses as visibly as mammals live with MBD in conditions that owners may not recognize as an emergency. Prevention through correct UV-B provision from day one is the only effective welfare response.