Lighting & UVB for Blue Tongue Skinks
UVB is a type of ultraviolet radiation naturally emitted by the sun. It’s critical to helping animals’ bodies make vitamin D3. Vitamin D3 is very important for building and maintaining strong bones, especially in diurnal reptiles. Vitamin D3 deficiency leads to Metabolic Bone Disease, discussed in the Health chapter of this guide.
Blue tongue skinks and UVB is a frequent topic of debate in the hobbyist community. It has been shown that BTS can be raised, bred, and maintained for decades without UVB, so technically it is not required for their survival. However, studies and veterinarians agree that dietary vitamin D3 and synthesized D3 (from UVB) are metabolized differently, and reptiles exposed to appropriate amounts of UVB have higher (read: healthier) levels of vitamin D in their blood as compared to those that are supplemented only.
Furthermore, UVB offers more benefits than just vitamin D, and the reptile community is increasingly coming to the conclusion that UVB should be provided to all reptiles as part of helping them thrive (not just survive) in captivity. Best practice in blue tongue skink care is to provide appropriate UVB lighting.
Placing Your Skink’s UVB
Zoo Med and Arcadia are the only UVB brands recommended by ReptiFiles. These are appropriate for use on top of or inside 18-24″ tall enclosures, and should be long enough to span half of the enclosure’s total length. In order to use these bulbs properly, they will need to be replaced every 12 months even if they seem to be working fine, since UVB output declines over time even though light output doesn’t. For the safety of the skink, it should be able to get no closer than 10″ to the bulb.
Also, make sure that the fixture doesn’t have a piece of glass or plastic to “protect” the bulb. UVB rays are blocked by glass and plastic, rendering that bulb you just spent so much money on completely useless. Naked UVB bulbs are effective UVB bulbs!
If you have a Solarmeter 6.5 (strongly recommended) to measure your lamp’s UVB output, shoot for a UV Index reading that ranges between 3.0-4.0 in the basking area. If you don’t have a Solarmeter, here is a rough estimate how far away your skink’s back should be from the UVB bulb during basking:
With mesh obstruction:
- Arcadia T5 HO Forest 6% — 6-9″ / 16-23cm
- Zoo Med T5 HO Reptisun 5.0 — 6-9″ / 16-23cm
- Arcadia T5 HO Desert 12% — 12-15″ / 31-38cm
- Zoo Med T5 HO Reptisun 10.0 — 12-15″ / 31-38cm
Without mesh obstruction:
- Arcadia T5 HO Forest 6% — 11-12″ / 28-30cm
- Zoo Med T5 HO Reptisun 5.0 — 11-12″ / 28-30cm
- Arcadia T5 HO Desert 12% — 17-18″ / 43-45cm
- Zoo Med T5 HO Reptisun 10.0 — 17-18″ / 43-45cm
Different T5 HO bulb fixtures affect the amount of UVB your skink will receive from the bulb differently. The distance given above are only accurate if the bulb is mounted in an Arcadia ProT5 or Vivarium Electronics T5 HO fixture.
UVB bulbs decay over time, so even if it still appears to be producing visible light, it may not be producing UVB! Make sure to change out your bulb every 12 months to maintain good UVB output.
Blue Tongue Skink Temperatures & Heating
Since blue tongue skinks are cold-blooded, they rely on their environment to provide the heat needed to function. The best way to achieve this is to provide a temperature gradient so the skink can self-regulate according to his/her needs. Use a temperature gun like the Etekcity Lasergrip 774 for instant, accurate information on your skink’s environment.
- Basking surface: 100-105°F (37-40°C)
- T. scincoides — 105-115°F (40-46°C)
- Australian species — 70-85°F (21°-29°C)
- Indonesian species — 75-85°F (24-29°C)
- Australian species — 65-75°F (18°-24°C)
- Indonesian species — 70-75°F (21-24°C)
Use a cluster of at least two high-wattage halogen flood bulbs inside of a dome heat lamp with a ceramic socket to safely achieve the right basking temperatures and thermal gradient. You can find the bulbs you need at the hardware store or pet store, but be sure to get halogen flood bulbs rather than rounded house bulbs. Halogen bulbs tend to last longer and burn hotter, so although they’re more expensive, they’re a better investment.
For an average 48″ x 24″ x 24″ enclosure, 100-150w should achieve the temperatures you need. Personally I’ve had good experiences with the Philips PAR38 90w Halogen Flood Heat Bulb, but the Arcadia Halogen Heat Lamp. If you find that gets a bit too hot, use a plug-in lamp dimmer to dial down the heat.
- Pro tip: If you still have trouble achieving the right surface temperature, try raising the basking area closer to the heat bulb or switching to a 90w halogen floodlight from your local home improvement store.
Blue tongue skinks generally do not need any kind of lighting or heating during the night. Some people prefer red or black bulbs for providing nighttime heat, but it’s actually healthier for skinks to experience a nightly temperature drop. However, without adequate daytime warming, these cool temperatures may induce brumation or illness.
If you need to heat your enclosure at night because it gets too cool, use a non-light emitting heat source like a ceramic heat emitter or radiant heat panel to warm the enclosure to an appropriate air temperature (not basking temp). These heat sources are not appropriate to use during the day, however.
Don’t forget to use a basking stone! In my experience I noticed dramatic improvements in my skinks’ activity and behavior after adding the stone, and I regret not installing one sooner. Take a piece of slate tile or flagstone and place it underneath the heat lamp. The stone will absorb heat from the lamp, providing warmth from both above and below in the same way that blue tongue skinks prefer to bask in the wild. If you want to have a healthy blue tongue skink, this is not an optional piece of terrarium furniture.
Never use a heat rock! These are not the same as a basking stone, since they are heated from inside with electrical wiring. Heat rocks are infamous for burning reptiles, so long story short: don’t do it.
Blue Tongue Skink Humidity Requirements
Maintaining the right humidity is important for helping your skink shed easily, as well as prevent illnesses like respiratory infections. As a general rule, Australian species thrive around 40% humidity, and Indonesian species require 60-80% humidity. However, this still varies depending on what species you have:
- T. gigas evanescens (Merauke) — 60-80%
- T. gigas gigas (Classic Indonesian) — 60-80%
- T. gigas gigas (Halmahera) — 70-100%
- T. gigas keyensis (Kei Island) — 60-80%
- T. nigrolutea (Blotched) — 40-50%
- T. multifasciata (Centralian) — 20-40%
- T. occipitalis (Western) — 20-40%
- T. scincoides chimaera (Tanimbar) — 60-80%
- T. scincoides intermedia (Northern) — 40-60%
- T. scincoides scincoides (Eastern) — 40-60%
- T. rugosa (Shingleback) — 20-40%
- T. sp. (Irian Jaya) — 60-80%
The best way to keep track of ambient humidity (and air temperature) is with a digital hygrometer like Zoo Med’s Digital Thermometer and Humidity Gauge Combo. Put the probe on the cool end of the enclosure and target the higher end of the animal’s humidity range. Enclosures tend to have humidity gradients just like they have temperature gradients, and trying to get the whole thing to have uniform humidity is an exercise in futility. Fortunately, that’s not how nature works, and reptiles know how to seek out places of higher/lower humidity as needed, so it works out.
A good rule of thumb for making sure your enclosure is humid enough is by checking your skink’s belly scales. If they’re rough, you need more moisture. If there’s nice and silky smooth and the skink is shedding well, you’re doing okay.
Tricks for maintaining humidity
Even when you use the right substrate, maintaining high levels of humidity can be tricky.
- Use a thick layer of substrate — at least 4″. The more substrate you have, the more moisture it can hold.
- Another trick is to set aside time each week to manually mix water into the substrate until it’s damp, but not wet. While misting only touches the surface, having moisture in the substrate stabilizes humidity for longer periods of time.
- Daily misting (preferably in the morning and/or at night) with a traditional spray bottle can give you hand cramps, so use a pressure sprayer like the Exo Terra Pressure Sprayer to make life a lot easier.
- Install a humid hideout somewhere in the middle to cool end of the enclosure. This will ensure that your skink has somewhere humid to retreat to during the day/night as needed. Simply line a reptile hide or cave with moistened sphagnum moss to encourage humidity levels near 100%, and replace the moss frequently to prevent mold from developing.
If you have a Halmahera, you may find that you still struggle to keep humidity high enough. If you’re on a tight budget, get a humidifier like the ReptiZoo Reptile Fogger. However, personally I recommend investing in an automatic misting system like the MistKing Starter system, as you’ll get more lasting humidity effects which will be better for your skink’s long-term health.
Here are 3 rules for using a reptile fogger successfully: