Action: Amphibians: Vary quality or quantity (UV% or gradients) of enclosure lighting to simulate seasonal changes in the wild
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- One replicated study in the UK found that there was no difference in clutch size between frogs given an ultraviolet (UV) boost compared with those who only received background levels. However, frogs given the UV boost had a significantly greater fungal load than frogs that were not UV-boosted.
For some species, breeding is seasonal and can be triggered by longer periods of sunlight. It may be possible to trigger breeding by simulating these cues within an enclosure.
In captivity, metabolic bone disease can be an issue in amphibians if the correct lighting is not used. It develops as a result of an imbalance of vitamin D3, phosphorous or calcium. Amphibians cannot process calcium without vitamin D, which is activated by ultraviolet light. If the correct lighting is not provided, animals can suffer from brittle or deformed bones. Health problems may affect reproduction in captive animals.
Supporting evidence from individual studies
A replicated, controlled study in 2014 in Manchester, UK found that there was no significant effect in clutch size for red-eyed tree frogs Agalychnis callidryas when given ultraviolet (UV) boost treatment, in conjunction with a diet supplemented with calcium. Two clutches were laid from two females in the background UV group (number eggs laid: 118), and four clutches from seven females in the UV boost group (184). There was no statistically significant effect of UV treatment on clutch size (background UV: 59; UV boost: 74). Frogs given the UV boost had significantly more fungal colony forming units (CFU’s) in comparison to frogs that were not UV-boosted (background UV: 2-3 CFU’s; pre-UV boost: 2 CFU’s; post-UV boost: 13 CFU’s). Forty frogs were used in four treatment groups, which started three months after their metamorphosis: background UV, 5% calcium diet; background UV, 10% calcium diet; background UV with UV boost, 5% calcium diet; background UV with UV boost, 10% calcium diet. Frogs receiving the “UV boost” treatment were put under a 300-watt Osram™ Ultra Vitalux mercury vapour sun lamp suspended 40cm above the base of the tank for 20 minutes. Breeding trials were conducted immediately after the UV boost trials.