Ultra violet light. What we know and what we don't know.

Ultra violet light, unseen by us humans, is necessary for most reptiles in order to create the vitamin D they need for healthy bones and a good immune system. Too much of it can cause skin and eye damage. Too little or none of it can cause a lack of vitamin D which in turn produces a vital hormone that regulates bone health and also the immune response.
Many reptile keepers who don't have UV light try to get round the need for it by dietary supplement of vitamin D or by feeding food that contains vitamin D, such as whole mice and rats. But we still don't know how much UV light most reptiles need. Sometimes a UV light is put into the vivarium and lights up the whole of it so the animal cannot escape exposure to it.
Yet in the wild reptiles regulate their exposure to UV light. In the same way they regulate their body warmth by basking. They will bask inUV as long as they need and then shelter from it. Therefore captive reptiles must be given a hiding place, or the UV light must be applied in such a way that they can move from a "hot" UV spot to a "cooler" UV spot.
Most reptile keepers have caught on to the fact that there must be a temperature gradient within the reptile enclosure, so that the animal can choose whether to be in a hot spot or a cool spot. Now we need to provide them with a UV light gradient too.  The heat lamp and the UV lamp should not be combined. A reptile should not have to choose to get too much UV light in order to get heat, or visa versa.
Gary Fergus and colleague decided they would try to work out how much UV light a reptile needed by looking at the animals in the wild and seeing how long they spent exposed to it. It was not easy.
They concluded that keepers of captive reptiles should provide a UV light gradient from maximum to minimum (by providing a refuge). That care should be taken not to produce vitamin D overose by too much supplementary dietary vitamin D.
So far so good. But they highlighted the lack of exact knowledge.
1. How long does each species of reptile in the wild expose itself to UV light?
2. How much vitamin D does the diet of wild reptiles provide?
3. What is the natural circulating level of vitamin D in a wild reptile?
4. How far can the reptile regulate its access to UV light according to its level of vitamin D in the body? ie. does it "know" when its vitamin D levels are low and does it therefore spend more time in UV light?
5. How sensitive is the reptile skin of different species to the absorption of UV light and conversion into vitamin D?
6. What is the ideal level of vitamin D for each species of reptile?
We don't know.

*

Gary W. Ferguson,1 Andrew M. Brinker,1 William H. Gehrmann,1 Stacey E. Bucklin,1 Frances M. Baines,2 and Steve J. Mackin (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, 317-334.

Birds have their nests, so do some reptiles.

Model of a dinosaur nest

Birds take care in choosing and making their nests. The successful hatching of the eggs and the survival of the young ones depend upon it. Egg-laying reptile also need to choose their nests with care. If they lay their eggs in the wrong place they may never hatch or survive after hatching.
The typical birds' nest is a construction of twigs, grass, leaves sometimes lined with mud or feathers. Reptiles don't do this. Instead they find a promising spot and dig a hole to lay their eggs in. Or put them in a burrow. Or pile up material to make a mound. Some lizards just lay eggs in cracks in the rock.
Some, the yellow spotted monitor lizard, dig complext tunnels or warrens where several lizards can deposit their eggs. Crocodiles heap up rotting vegetable matter and lay their eggs on the top of it. The nest is usually at the water's edge so that the hatchlings can get to the water easily.
Turtles dig a hole and lay their eggs in just one night. But Tuatara and green Iguanas will spend several nights constructing a proper burrow for their eggs. If they don't get it right, the eggs may never hatch. The longer incubation period required for reptile eggs puts them more at risk than birds' eggs.
Unless warm blooded birds that sit on their nests to keep the eggs warm and hatch them, most reptiles do not brood their eggs. So it is all the more important that they lay the eggs in a place where they will be warm enough. This means that there must be the right balance of sunlight and shade for eggs that are laid in the open air. Burrowing reptiles can make the burrow shorter or deeper according to th temperature they need.
The warmth of a nest site affects the offspring - the size and even the sex. Unfortunately because reptiles rarely brood their young, the individual reptile cannot know if her eggs have hatched successfully. If birds lose a clutch, they will often find a different nest site and lay second clutch of eggs to compensate. Reptiles can't do this.
Therefore climate warming is likely to affect reptiles more than birds -- and may alter sex ratios drastically.

*Refsnider,J.M., (2016), 'Nest choice and nest construction in reptiles,' Available at www.avianbiologyresearch.co.uk
Paper 1500632 doi: 10.3184/175815516X14490631289752
Accessed November 4 2016.

Ultraviolet light - your lizard needs it for communicating..... don't keep it in the dark

RobinSings. https://en.wikipedia.org/wiki/Puerto_Rican_crested_anole

Lizards can see colours that we see and they can see colours we don't see - the colours in ultraviolet light. And colours matter to them, because they communicate with each other using colour signals. If they couldn't see ultra violet colour, it would like being colour blind for a human. And worse, because where we use words, they use colour to "speak."
Anoline lizards, arboreal American lizards, use their dewlaps to communicate.  They open and close them, making a sort of colour flash, rather like (but not very like) light signals used in morse code from ships. The brightness of the colours and how they stand out from the background makes them effective signals. Male lizards sit up on a high perch or branch, and flash their dewlaps to attract females and deter male rivals from a distance. Dewlaps are coloured differently in different species, probably to make sure that they show up in different habitats.
The females and rival males "capture" the signals with their eyes which have special cones. One type of cone is specialised for ultraviolet light. (Humans don't have this kind of cone.) Scientists tested Puerto Rican crested anoles to see what happened if there was no ultraviolet light visible. The lack of ultraviolet meant that the signal looked less bright to the lizard. The signal (which simulated a dewlap flash) just looked dark against the background.
Moreover, ultraviolet light helped the lizard detect motion. A dewlap flash is only a flash if it stops and starts, so detecting motion is important. Detecting motion in all animals, including humans, seems to depend on the contrast between signal and background which is more noticeable for a lizard sees the ultraviolet light.
So if we are keeping lizards in vivariums with no ultraviolet light - or where the UV lighting has failed - we are keeping them in the dark. Not only are they not getting the UV light they need for vitamin D (which means low immune system and poor bones), but they are living in a dull dark world where they cannot communicate properly.

For more read:  Fleishman, L. JJ. & Persons, M., (2001), 'The influence of stimulus and background colour on visisbility in the lizard, Anolis cristatellus, The Journal of Experimental Biology, 204l 1559-1575

How do you know if your lizard, or your snake, or your tortoise is stressed?

Muhammed Mahdi Karim photo is here

When animals are under stress, the nervous system responds by releasing adrenaline and other hormones to prepare the body for action. The adrenal glands flood the body with hormones like adrenalin (epinephrine) to prepare the animal for action. Similar hormones are produced in the brain.

For a long time it was thought that cold-blooded animals were “primitive” and therefore did not suffer from stress as much as “higher” animals.Yet reptiles respond in a very similar way to warm-blooded mammals, though their adrenal glands and their hormones are slightly different.

If the snake or lizard or tortoise has to run away, or hide, or do something in response to a threat, then these hormones help them to do it. For instance some lizards shed their tail when chased by predators. But if there is no action available, the hormones just flood the system to no avail. The animal has no relief from emotions like fear. Reptiles in bad conditions of captivity that cannot escape, for instance, will experience the emotion of frustration in countless escape attempts.

This means that they suffer.

And if the stress is chronic, this affects the animal’s welfare. Chronically stressed reptiles (and humans) have a lowered immune system. They are more likely to get various diseases and disorders.

One problem in measuring tis in reptiles is that their response will vary according to their temperature. They cannot produce their own body heat, so when a reptile is cold, its body functions slow down. So the stress hormone levels in a cold reptile will be different from the stress hormone levels in a warm one.

What can we look for? We can look for harmful repetitive behaviours, like the way lizards or tortoises repeatedly push at transparent barriers. We can look for lack of appetite, aggression, and even a change in skin colour in some lizards.  We need to know how a normal reptile behaves, before we can tell how a stressed one behaves.

What can we look for? Diseases and disorders due to stress may involve inability to reproduce, susceptibility to infections, emaciation from lack of appetite or its opposite, obesity.

What can we look for? We can measure the stress hormones or other chemicals in the blood, but taking blood samples, for instance, will cause even more stress. Or we can measure them in the faeces – a better way as it doesn’t hurt the animal.

But….. we don’t still know enough about what is normal for a corn snake, say, or a crocodile, or a boa constrictor, or a Hermann’s tortoise, or a bearded lizard. Each species may differ in the way it responds to stress. We have a lot of research to do.

Read

Silvestre, A. M. (2014) ‘How to Assess Stress in Reptiles, Journal of Exotic Pet Medicine, 23, 240-243.

Too much or too little vitamin D for reptiles? What do we know so far?

Some lizards may use basking not just for heat but for UV light.

By now most reptile keepers realise that too little vitamin D is bad for reptiles. Vitamin D is either absorbed through natural light or through the diet. Although carnivorous reptiles can get vitamin D in their diet: strictly herbivorous reptiles will not get enough just from diet. And it now looks as if relying on diet along, even in carnivores snakes, risks vitamin D inadequacy.
What do low levels of vitamin D do? Vitamin D is important for the growth and development of bones, for the immune system, artery and vein health, and reproduction. So low levels will impact badly on all these functions. We now know for sure that good vitamin D levels are important for the successful reproduction of several captive reptile species.
Vitamin D can be found in supplements that are given to reptiles. But there is a downside to this. It looks as if dietary vitamin D can lead to too high a vitamin D level if supplements are used incorrectly. In reptiles with an overdose of vitamin D, the aorta gets furred up with minerals.  So supplementing vitamin D by diet can be tricky.
Vitamin D levels are also affected by ultra violet light. But there have been no reports yet of vitamin D overdosing because of UV light. Yes, there can be skin damage from "too much" UV light but not vitamin D overdose. There seems to be a mechanism in the skin hat prevents overdose.
So.....
It is safer to use UV lighting or access to natural daylight to give your reptile enough vitamin D. The animal can probably regulate its vitamin D levels to prevent overdose.
Moreover, some (probably not all) carnivorous captive reptiles that get their vitamin D from a diet of mice etc. may well benefit from UV lighting as well. Carnivorous Komodo dragons get more vitamin D from UV light than dietary vitamin supplement. Conversely ball pythons were able to get their vitamin D equally well from either.
What is the take-home message from this? Use of dietary supplements may not be enough and risks overdose if used incorrectly. UVB light on its own will not lead to overdose and is therefore safer. Some reptiles will benefit it even though they get vitamin D from a carnivorous diet.
AND MOST IMPORTANT OF ALL - Keep up with modern developments. This is an area which is still being researched. What was best practice ten years ago is not best practice now. If you think you know it all, you probably don't.

To read more about this go to:

Watson et al (2014), 'Vitamin D and ultraviolet B radiation considerations for exotic pets,'Journal of Exotic Pet Medicine, 23, 369-379.

 

How iguanas need their vitamin D - from light or a supplement?

There are two ways to get vitamin D - eat it or absorb it through the skin from light. Does it matter which? In the wild green iguanas would regulate their body temperature and their vitamin D by basking in the sun (an ultra violet light source) then going to the shade (without ultra violet light) when too hot. As they are herbivores they cannot get the vitamin from their food.
In 2004 a study suggested that dietary supplements of vitamin D were a good source rather than UV light. The problem with UV light then was that a reliable source of light was then not available.
You will find the details of the study here - http://www.anapsid.org/pdf/jody-hibma-uvb.pdf
In l996, a more complicated study was set up. This time different lighting was used and some of the iguanas showed very high levels of vitamin D, if they were given both a dietary supplement and an UV light. Strangely, though, these high levels didn't seem to poison them - though igs have been known to die of vitamin D overdose. Read the full account here - http://www.anapsid.org?iguana/bernard-d3.html.
So do iguanas need UV light and dietary supplements. They certainly need UV light and when you do put in UV light, you must give the iguana a place in the shade where it can escape the light if it chooses. It will regulate its temperature so the UV light needs to be in the same place as the heat lamp. If it is not the lizard will spend most of its time in the heat lamp area and miss the benefits of UV lighting.
Do they need a vitamin supplement as well? This seems to be doubtful. A lot of the general reptile supplements on the market will do them no good and may do harm. Again, read up on the topic here - http://www.anapsid.org/vitamin.html
It's difficult. It's complicated. And we don't know as much as we should. All this means that a green iguana is a pet for the experienced reptile person, not for a beginner.

Do corn snakes need or want ultra violet light? The vitamin D question.Pete Milligan of Evolution Reptiles

Pete Milligan of Evolution Reptiles, Kidlington

For years it had been thought that corn snakes, a popular and easy reptile pet, don't need special lighting. They just need a heat gradient and a proper diet of defrosted rodents.  The vitamin D which they needed came from their diet (just as cats and other carnivores get their vitamin D from their diet).
Vitamin D is essential for health. It regulates the calcium that is needed to make bones. Studies of vitamin D in humans and birs and mammals are beginning to show that it is essential for good health in other ways, possibly playing a protective part against human breast cancer. All in all it is an important vitamin.
We still don't know for sure how much vitamin D is needed by various reptiles. Do corn snakes need it via ultra violet light? Is their diet giving them enough? Corn snakes, if they are fed the correct diet (not the mince that was recommended as feed for snakes in Ireland in the l960s!), should have enough vitamin D to survive.  But what is enough? Enough to survive? Enough to breed? Enough to flourish?
A group of scientist in Louisiana State University investigated further (see below). Over 4 weeks during which the snakes were not fed, they exposed one group of snakes to UVB radiation, and one group were kept without it. They tested the level of vitamin D in the blood. The levels of radiation were also measured.
The group without UVB radiation showed no change in their vitamin D level: the group with UVB radiation had a higher level of vitamin D. So corn snakes can and will increase their vitamin D level if they are exposed to ultra violet light.There was no significant difference between the two groups in weight at the end of the period.
So now we know for sure that, given UV light, corn snakes will make vitamin D from it, and have a higher level of it in their bodies than a level just obtained from their diet. We can no longer make the assumption that UV lighting is unimportant for corn snakes. "The findings of the present study suggest otherwise," say the scientists. This is the first step towards finding out how important it may be and what levels are needed not just for survival but for good health and happiness (yes, reptiles do feel emotion!).
Pete Milligan of Evoluton Reptiles says: "A snake will benefit from UV - at the moment there isn't enough evidence to say that it is essential."

• The reptile relationship survey has now closed. Thank you everybody who did it.

• *Acierno et al., 'Effects of ultraviolet radiation on plasma 25-hydroxyvitamin D3 concentrations in corn snakes (Elaphe guttata),' American Journal of Veterinary Research, 69, 294-297