Regulation of Exposure to Ultraviolet Light in Bearded Dragons (Pogona vitticeps) in Relation to Temperature and Scalation Phenotype

Abstract

Exposure to ultraviolet (UV) light has both physiological benefits as well as costs. Many lepidosaur reptiles can behaviorally self-regulate their exposure to UV light in order to take advantage of the benefits of UV light while minimizing the costs. Furthermore, lepidosaur scales have been conceptualized by some as a barrier to the penetration of UV light. Here we examine regulation of self-exposure to UV light in three different phenotypes of Bearded Dragon (Pogona vitticeps): wild type, animals exhibiting scales of reduced prominence (‘Leatherback’), and scaleless animals (‘Silkback’). Silkbacks on average chose to expose themselves to lower levels of UV light irradiation than Leatherbacks or wild types did. Bearded Dragons of all scalation phenotypes on average received higher UV irradiation when they were in the cold section of a UV gradient apparatus compared to when they were in the hot section of the apparatus. This either demonstrates that Bearded Dragons under higher UV irradiances choose cooler temperatures or demonstrates that Bearded Dragons at cooler temperatures choose higher UV irradiances. The relationship between chosen temperature and chosen UV light irradiance was not affected by scalation phenotype. This study highlights external influences on the mechanism that regulates UV self-exposure behavior in lepidosaur reptiles.