Licht-im-Terrarium: Literaturdatenbank

The male Komodo dragon Chidra moved from the outdoor enclosure to the indoor enclosure, and the female Tia from the indoor enclosure to the outside. Behavior, UV radiation and vitamin D3 blood levels were measured.

 

In this context, the zookeepers recognized that the UV lighting in the indoor facility was inadequate and tested 11 lamps or lamp combinations with solar meters 6.5 and 6.2 to find a suitable lamp. The results of the lamp tests (7 distances 1 inch to 8 feet = 2.5 cm to 2.40 m) and 3 positions (central and 6 inch = 15cm left and right) fill two full pages in the paper. The lamps tested were compact fluorescent lamps (ExoTerra UVB150 26W, ZooMed Reptisun 10.0 13W), several self-ballasted mercury vapour lamps (T-Rex 160W, ReefBrite 100W, ReefBrite 160W, ZooMed Powersun 160W, MegaRay 275W) and T5 HO tubes (ZooMed Reptisun 39 W 5.0, with 1 , 2, 3 and 4 tubes). That's a considerable amount of effort for a zoo!

 

The decision fell on the ReefBrite 160W lamp, which achieved UVI 4.1 in the center and 0.4 every 15 cm to the sides at a distance of 2.40 m. The combination of the four T5 tubes only achieved UVI 0.7 at a distance of 2.40m. They didn't want to hang the lamps any closer so that animals couldn't damage the lamps.

I don't think this choice is optimal. A different combination of T5 tubes, for example for the Komodo dragons in the ZLS London Zoo (Baines2014), seems more sensible to me: There are several ways to increase the UVI: stronger tubes (10.0 instead of 5.0), more tubes (6, 8, ... instead of 4) and longer tubes (54W instead of 39). The measurement UVI 5.1 at 6in distance itself agrees with measurements from other reptile owners for 5.0. A coarse mesh grid could protect the tubes at shorter distance. Even the solution with 1000W UV-HQI lamps like the Komodo dragons in the House of the Sea in Vienna (Fischer2021) would be an alternative (even if I don't like the spectrum of these lamps very much and the aging is questionable here too). But a 160W mercury lamp is not enough.

 

The lighting was changed 4 months after moving into the indoor terrarium. However, the ReefBrite lamp has lost almost all of its UV content after just 3 months (quite typical for self ballasted mercury vapour lamps).

 

The female's blood values rose from 50 ng/mL (125 nmol/L) to 100 ng/mL (250 nmol/L) when she moved to the outdoor enclosure, but then fell back to the initial value. The phase with higher blood values includes egg laying (with egg development) but also inflammation of the ovaries, which was operated on. It is therefore unclear to me to what extent the D3 blood values were influenced by the better UV supply or by other processes in the body. The authors also discuss this. What remains remarkable, however, is that the 8-year-old animal's move resulted in the laying of its first eggs in 2.5 years.

 

The 200 nmol/L seems to be within the normal range for Komodo dragons (Gillespie2000, Nijboer2003).

 

In the male, the blood values remained constant at around 80 ng/mL (200 nmol/L) during the approximately 6 month observation period. This does not prove that the UV or vitamin D supply is sufficient. Other studies (which the authors cite) also show that blood values remain constant over a few months even without supplements or UV.

The male's behavior was observed several times in the three periods "outside", "inside before changing the lamp", "inside after changing the lamp" for a few minutes and was classified into the categories "rest", "stationary", "locomote", "climb" , “feed”, “dig”, “other”. When moving from outside to inside, the male moved less and rested more. This behavior returned to the old pattern when the lamp was changed - at least if you look at the times not separately for three times of the day but averaged over the day. I'm not entirely convinced that a single 160W mercury lamp is enough to cause a Komodo dragon to change its behavior in a "sun-like" way. I also think it is possible that the monitor lizard changed its behavior due to the abrupt change from outside to inside and then found its way back to its “personal preferences” over time.