Dr Frances Baines runs through the what, why and how of using Solarmeters – a must have under the new AAL laws and the best way to keep track of UVB outputs for reptile health.

About the Solarmeter
There are two models of the Solarmeter – the 6.5 and the 6.5R. The ‘R’ stands for ‘reptile’, but these are exactly the same meter. The 6.5R is simply branded for use with reptiles and comes with an instruction leaflet which provides information that reptile keepers will find useful. The 6.5 is marketed for people measuring human tanning lamps and sun exposure. If you have a 6.5 you should ignore the ranges you see shown in the illustrated table above the reading window. The meter runs on a single 9V battery in the compartment at the back of the meter. With average weekly use, the battery may last up to three years or more.

Here the 6.5 and 6.5R measure the same reptile lamp at the same distance. As expected, the readings are identical. In the lefthand image you can see the illustrated scale is not relevant for reptile keeping so be sure to ignore if you are using a Solarmeter 6.5.

What UV level does the animal need?
Very few field studies have measured UV levels experienced by wild reptiles in their native micro-habitats. The UV an animal experiences varies widely depending upon the time of day it is active and its behaviour at that time  A pioneering series of UV recordings by a team of herpetologists following wild reptiles (Ferguson et al. 2010), led the authors to categorise each species into one of four basic UV exposure ‘zones’ depending on their typical behaviour and habitat.

The British and Irish Association of Zoos and Aquaria have published guidelines, using these ‘Ferguson Zones’ to suggest suitable UV levels for a very wide range of other species, based on their similar behaviours and habitats.

The full guidelines can be downloaded from:
www.jzar.org/jzar/article/view/150/89
(Baines et al. 2016)

1 Ferguson, G.W., Brinker, A.M., Gehrmann, W.H., Bucklin, S.E., Baines,
F.M. and Mackin, S.J., 2010. Voluntary exposure of some western
hemisphere snake and lizard species to ultraviolet B radiation in
the field: how much ultraviolet B should a lizard or snake receive in
captivity?. Zoo Biology, 29(3), pp.317-334.

2 Baines, F., Chattell, J., Dale, J., Garrick, D., Gill, I., Goetz, M., Skelton,
T. and Swatman, M., 2016. How much UV-B does my reptile need?
The UV-Tool, a guide to the selection of UV lighting for reptiles and
amphibians in captivity. Journal of Zoo and Aquarium Research, 4(1),
p.42. Download from: https://www.jzar.org/jzar/article/view/150/89.

Before you start
1. Ensure that the UV lamp has been on for at least 30 minutes and is fully warmed up.

2. For each vivarium, decide upon a position where you will always take your readings. This should be the closest position the reptile can get to the lamp. With basking species, this should also be the place where the reptile basks since the UV and basking heat need to overlap. Ideally you should take the reading at ‘reptile height’ to measure the UVI the animal’s back will receive. The reading at this point should be within the suggested optimum range for that species.

UV lamps are often positioned behind a mesh screen, usually when arboreal snakes and lizards are housed in glass terrariums. In these circumstances it is necessary to measure the UVI extremely close to the mesh, at the closest position the animal can get to the lamp. The UVI at this point must be within the safe maximum exposure level for the species.

Taking a reading
1. Aim the sensor at the UV lamp. Be sure not to touch the sensor with your hand or hold it against the surface of the lamp, mesh screen or other hard surface.

2. Press the on/off button and keep it pressed down. The meter only stays on while the button is depressed.

3. Look at the LCD display. It gives the amount of UV reaching the sensor in UVI units.

• 00.3 is UVI 0.3 – very low
• 03.0 is UVI 3 – good for many basking species
• 13.5 is UVI 13.5 – dangerously high

4. Using very slow, small movements, tilt the meter to scan for the best alignment in your chosen position. You are looking for the angle which will give you the highest reading on the display. This is the reading you should record.

5. Record your reading. If you are monitoring a lamp for decay, repeat your readings from this same position, weekly or monthly as appropriate. Most lamps will lose a noticeable proportion of their UVB in the first few weeks during the ‘burning-in’ period, after which time lamps from a reliable manufacturer should only decay very slowly over their expected lifespan.

Replace the lamp only when its UVI reading falls below the desired level at the reptile’s basking position.