Zoo Med Digital UV Index Radiometer - Manual (Page 3)

HOW DOES THE UV INDEX METER COMPARE TO UVB METERS?
You may already be using a handheld UVB radiometer to measure UV lamps and the
sun. Common examples include Zoo Med’s model ST-6 UVB meter, and the Solartech
model 6.2 UVB meter. UVB meters are useful for determining whether or not a lamp is
emitting UVB, and also for tracking the decay in UVB over time (called depreciation).
They are not ideal for making comparisons between different types or brands of UVB
lamps. Also, they are not useful in determining if a lamp is both safe and effective for
use with reptiles. In fact, at a set distance, two lamps can produce very different UVB
readings, but have the same UV Index reading (and vise versa).
Since the UV Index meter only “sees” the wavelengths that contribute to vitamin D
synthesis, as well as eye/skin damage, it can be used for the following:
- To determine if a lamp is safe for use with reptiles.
- To determine the appropriate distance from the lamp to the basking site.
- To make comparisons between different types and brands of lamps, and between
lamps and the sun.
HOW DOES THE UV INDEX APPLY TO REPTILES?
The UV Index was developed as a tool for evaluating human risk of UV exposure
outdoors. So how do we use it to evaluate UV lamps designed for use with reptiles in
terrariums? This question was approached scientifically by a team of researchers led
by the prominent herpetologist; Gary Ferguson, Ph.D. In their study, they took UV
Index readings throughout the day in locations where they observed different species
basking outdoors in sunlight or living in the shade. Using these UV Index readings,
they were able to make recommendations for appropriate UV levels by creating four
different UV Index “zones.” These zones were named the “Ferguson Zones” by
Frances Baines (one of the authors and noted reptile photobiologist).
UVI: 0 to1 1 to 2 2 to 3 3 to 7 >7
ZONE: I II III IV DANGER
MINIMUM
MODERATE
HIGH
FERGUSON ZONES:
I 0.4 TO 0.7 (SHADE/CREPUSCULAR)
II 0.7 TO 1.0 (MOSTLY PARTIAL SUN - OCCASIONAL FULL SUN)
III 1.0 TO 2.6 (MOSTLY FULL SUN - OCCASIONAL PARTIAL SUN)
IV 2.6 TO 3.5 OR MORE (MID DAY BASKERS)
WHICH ZONE IS RIGHT FOR MY SPECIES?
Zone 1: UVI 0.4 to 0.7 (Shade/Crepuscular)
Species in this zone can be either diurnal (active during the day) or crepuscular
(active at dawn or dusk). They avoid direct sunlight exposure and are able to meet
their vitamin D requirements through exposure to low levels of UVB typically found in
the shade, or at dawn or dusk.
IMPORTANT NOTES (Continued)
Shade method vs. Sunbeam method: Two methods of providing UVB for reptiles
are described by Frances Baines. Ferguson UVI zones 1 and 2 approximate UVB
levels that would be found in the shade, in the canopy of a tree, or on partly cloudy
days. These levels are often achieved over the majority of the habitat using fluores-
cent lamps that span the length of the terrarium, just as the levels would be
uniform outdoors in the shade or on an overcast day. When providing UVI for zone 3
and 4 species, ideally, the Sunbeam method should be used, where the appropriate
zone is provided over about half the length of the terrarium, and higher levels (in
the range UVI 3.0 - 7.0) are created over just the basking site, to simulate direct
sunlight. A gradient down to zero UVI is achieved in the rest of the habitat.
Temperature gradient: The biological process where vitamin D is synthesized in
the skin following exposure to UVB can only occur when the proper temperatures
are present. This process is heat dependent, so it is critical to research the
temperature requirements of various species and provide the “POTZ” (preferred
optimum temperature zone) in their habitat. Whenever possible, place the heat
source as close as possible to the UVB source.
Watch for abnormal behaviors: It is important to monitor the reptile’s behavior
following the introduction of a new UVB lamp. If the reptile spends unusually long
periods of time basking as close as possible to the UVB and heat lamp(s), then the
temperature and/or UVI level may be too low for that species. If a species appears
to be trying to avoid the UVB lamp, spending most of its time as far from the lamp
as possible then the lamp may be too strong. Under ideal conditions, reptiles should
spend some time basking, and should also move throughout the habitat to perform
natural behaviors (feeding, sleeping, etc.). Be sure to check both the UVB and
temperature levels in the habitat.
Reflectors and screen mesh: Reflectors can have a great effect on the total UV
output from a lamp, sometimes increasing the measured UV output by 30% or more
when an effective reflector is used. Be sure to test your lamp in the fixture that will
be used on the habitat. Additionally, screen mesh between the lamp and the
basking site usually causes a significant reduction in UVB. The percentage of UVB
reduction varies with different types/sizes of mesh. Be sure to check UVI levels
through the mesh to determine the percent reduction caused by the mesh being
used. Glass and most plastics filter all UVB emissions and should not be placed
between the lamp and animals.
Lamp brightness: Lamp brightness is measured in lumens or lux. Lumens is a
measure of the total light emitted by a lamp and can only be measured with highly
specialized equipment. Lux is another measure of brightness, and measures the
amount of light that is cast over a given area (lumens/meter). This can be measured
with affordable handheld meters. It is important to consider the amount of light that