Mourning geckos are perceived as nocturnal, but the truth is that they are cathemeral, which means they are irregularly active throughout the day and night. Because of this mistaken assumption, people also assume that UVB lighting is not beneficial. However, mourning geckos can and will bask under UVB lighting if it is provided, and I have noticed that providing UVB makes a significant difference in healthy growth for hatchlings in particular.
Wild mourning geckos are commonly observed basking and being otherwise active during the day, especially in the morning. In fact, I have found that my own colony becomes very active at “dawn,” or when the lights first turn on in the morning, and sometimes I wake up to their chirping.
Furthermore, UVB bulbs also produce UVA light, which is a spectrum of light that reptiles can see but humans can’t. They see it like an additional color. In other words, depriving reptiles of UVA light is like giving them the equivalent of the red/green color blindness that is sometimes present in humans.
Mourning geckos are Ferguson Zone 1-2 reptiles, and should receive a UVI of 1.0-3.0 in the basking area. This should be the area of highest temperature and UV in the enclosure.
The strength of UVB that a reptile is exposed to decreases in proportion to increased distance from the bulb. Given that mourning geckos have a habit of hanging out upside-down on the top mesh of their enclosure and are not afraid to do so directly under a light, it’s extremely important to choose a UVB bulb and fixture that are safe to use at such a short distance.
These are my picks for the best UVB equipment to use with mourning geckos:
To increase the distance between the UVB lamp and the top of the enclosure, prop it up with some narrow wood blocks or similar until you reach your target basking distance.
The above distance recommendations assume a ~30% mesh block. It is strongly recommended to use a Solarmeter 6.5 to double-check your UVI directly under the lamp and make adjustments as needed. For more details on adjusting basking distance based on mesh obstruction, see the Facebook group Reptile Lighting > Guides > Guide 1: Using T5-HO lamps above a Mesh Screen.
The UVB bulb should span most of the enclosure’s length to create a vertical light gradient and ample basking sites to reduce competition.
Photo contributed by Woodland Manor Darts and Dragons @WMD_n_D