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Fool Proof Guide to UV Lighting for Reptiles

Updated: Aug 20, 2021

UV lighting for reptiles is a hot topic and one that was fairly misunderstood for a long time. Now the hobby's understanding of UV light and the animals requirements has improved there is much more information available to help prevent pet owners from getting it wrong. Near enough all animals that are kept in captivity require some level of UV exposure to mimic a natural environment.

What is UV light?

UV lights used in captivity are replicating the natural sunlight that all animals that live outside are exposed to. The 2 waves of light that are important to animals health are UVA and UVB.


UVA in simple terms is visible light and is responsible for 95% of the suns UV rays. UVA is important for reptiles as it assists them in regulating natural behaviours such as feeding. Animals that would naturally feed during dawn and dusk require UVA light to follow such a feeding pattern. As well as assisting in other natural behaviours such as mating.


Like us, a reptiles skin is responsible for producing vitamin D. Upon providing your pet with UVB, you are recreating its natural exposure to sunlight whereby the UV penetrates the skin. Under the influence of the correct temperatures within the vivarium, it allows the pro vitamin D3 which your reptile has produced to change to pre vitamin D3. It is impossible for the body to absorb and use calcium without Vitamin D. It is recommended to provide your pet with a natural way of creating D3 alongside supplementation, to prevent against commonly seen and preventable diseases such and MBD (Metabolic Bone Disease) and calcium deficiency.


To measure the amount of UV rays that a given source is producing, we use a guide called the UV index. The same guide that weather reporters use to advise on the suns strength. The UV index, or UVI goes from 1 up to to 11+ and reptile keepers can use this guide to measure the wavelengths that allow our reptiles to produce their own vitamin D3. As our pet reptiles originate from different habitats all over the world and have different lifestyles, they are subjected to differing amounts of UV exposure.

Ferguson Zones

To make things a little simpler, the UVI has been condensed into 4 zones, known as the Ferguson Zones named after the Herpetologist that studied common pet reptiles basking UVI's. Most species kept in captivity can now be divided up into the 4 Ferguson Zones making it much easier for the keeper to provide their pet with the correct level of UVB.

Zone 1

Zone 1 mainly includes animals that are crepuscular, or active at dawn and dusk. It includes a UVI range of 0.7-1.4. Commonly kept reptiles that belong in the Zone 1 range-

  • Leopard Gecko

  • Crested Gecko

  • Pacman Frog

  • Fire Bellied Toads

  • Corn Snake

  • Pueblan Milk Snake

  • Fire Salamander

  • African Bull Frog

  • Cave Gecko

  • Axolotl

  • Emerald Tree Boa

  • Childrens Python

  • Henkels Leaf Tail Gecko

  • Tomato Frog

  • Red Eye Tree Frog

  • Reticulated Python

  • Satanic Leaf Tailed Gecko

  • Sinaloan Milk Snake

  • Solomon Island Boa

  • Green Tree Frog

  • Viper Gecko

  • Woma Python

  • Poison Arrow Frog

  • Mountain Horned Dragon

  • Mourning Gecko

  • Burmese Python

Zone 2

Zone 2 includes all occasional basking species that thermoregulate. It includes a UVI range of between 1.1-3.0 . Commonly kept reptiles that require Zone 2 levels of UV include-

  • Asian Water Dragon

  • Electric Blue Day Gecko

  • Jacksons Chameleon

  • Fire Skink

  • Royal Python

  • Gargoyle Gecko

  • Kenyan Sand Boa

  • Rat Snake

  • Rough Green Snake

  • Tri Coloured Hognose

  • Western Hognose

  • Mellers Chameleon

  • Moorish Geckos

  • New Caledonian Giant Gecko

  • Ornate Box Turtle

  • Painted Wood Turtle

  • Whites Tree Frog

  • Red Foot Tortoise

  • Taiwan Beauty Snake

  • Razor Back Musk Turtle

  • Garter Snake

  • Fiji Banded Iguana

  • African Fat Tailed Gecko

  • Hog Island Boa

  • Gopher Snake

  • Golden Mantella

  • Mexican Black Kingsnake

  • Nelsons Milksnake

  • Plumed Basilisk

  • Pancake Tortoise

  • Pink Tongue Skinks

Zone 3

Zone 3 includes all partial sun baskers that are thermoregulators. It includes a UVI range of between 2.9-7.4. The most commonly kept species that require Zone 3 levels are-

  • Bearded Dragon

  • Hermanns Tortoise

  • Yemen Chameleon

  • Green Iguana

  • Leopard Tortoise

  • Tegu

  • Berber Skink

  • Ackie Monitor

  • Collared Lizard

  • Tree Monitor

  • Carpet Chameleon

  • Cuban Knight Anole

  • Curly Tailed Lizard

  • Eyed Lizard

  • Emerald Swift

  • Rankins Dragon

  • Panther Chameleon

  • Parsons Chameleon

  • Reeves Turtle

  • Painted Turtle

  • Red Eared Slider

  • European Pond Turtle

  • Greek Spur Thighed Tortoise

  • Horsfield Tortoise

  • Hinge Back Tortoise

  • Gold Dust Day Gecko

  • Lace Monitor

  • Indian Star Tortoise

  • Kimberely Rock Monitor

  • Mediterranean Pond Turtle

  • Oriental Garden Lizard

  • Radiated Tortoise

Zone 4 Zone 4 includes all sun worshippers that remain in the sun far longer than zone 3 animals. It includes a UVI range of between 4.5-8. The most commonly kept species that require Zone 4 levels are-

  • Chuckwalla

  • Blue Spiny Lizard

  • Butterfly Agama

  • Cuban Rock Iguana

  • Desert Horned Lizard

  • Lesser Earless Lizard

  • Marginated Tortoise

  • Moroccan Uromastyx

  • Occelated Uromastyx

  • Ornate Uromastyx

  • Red Head Agama

  • Rhino Iguana

  • Saharan Uromastyx

  • Spiderman Agama

  • Starred Agama

  • Sungazer Lizard

Your reptiles enclosure should include a natural gradient, not only for heat but also for UV light. This means having a basking side that is suitable for your species and matches its Zone requirements right down to an area that receives 0 UV such as a hide. It is important that all animals in all Ferguson Zones can retreat away from the "sun" when they want to. Most UVI readings are taken from around 30cm from where the animal will be basking. It is important to take into consideration anything that may be blocking the UV light source and reducing its efficiency such as guards or mesh vivarium lids. UV light bulbs do lose there effectiveness over time and it is important to change them according to the manufacturers instructions. As a general rule compact bulbs and T8 bulbs should be changed every 8 months and T5 and Mercury Vapour bulbs every 12 months. Hopefully this makes it a bit easier for you to chose the correct lighting for your pet reptile. If your pet is not listed please get in touch and we can recommend an appropriate bulb for you.

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