Just to clear a few things up.
A crepuscular animal is defined by its tendancy to be more active or more accurately more commonly "Seen" before 11.00am and after 6pm. as you know there is plenty of light in these periods.
Crepuscular animals use the sun and the energy from the sun in exactly the same way as desert reptiles and have exactly the same response to the D3 cycle. They are in effect the same animals but they have developed an ability to hide away from the heat and dangers of the day. This has provided them with a thinner skin that provides less protection against the full index of the sun and allows them to suck in rays in lower light and in a quicker perioed of time.
They do have skin and bones and as such do require access to D3 to allow the assimilation of Ca. They do also suffer from MBD. MBD is only ever found in captive animals which for me simply means that we all as keepers still have much to learn from nature. In the wild this is maintained safely through and after exposure to the sun. You cannot over dose a reptile with D3 after exposure to UV rays in the same way as you can poison it with suppliments. Over provision from the natural D3 cycle is passed through the system whereas over supplimentation is not.
These animals will generally spend a few mins here and there in columns of light and wedged in logs and branches or in rock networks. Darting out for a few mins to feed and carry out day to day tasks. They will do this more in the crepuscular times of the day. They can and do use sunlight like all living things but due to the thinner skins take far less time to do so.
What we as keepers need to do is to provide an environment that replicates the wild environment. We need to find out the average UVindex of that area and look at the activities of the species. Tokays are by nature secretive having been predated for years and years but they do use shafts of light and can be seen to expose themselves fully for a few mins at a time. Dont forget they can see UV and will select the area that they need to be in.
After we have decided on the correct average index and matched this with the habitat through decoration we can then use the height of the viv to choose what lamp is required to re-create the index.
So if it were me and I had a Tokay in a viv that was 3 foot high by 2 foot wide and 18 inches deep I would use a 6% 14w 15" lamp fitted into the hot side of the viv and to the roof.
This then means that 9" of the viv is allowed to drop off into shade at the cool end. I would then decorate the viv to provide lots of coverage and areas in which the animal can self regualte.
We believe that self regulation of animals is key to the successfull lighting of enclosures and is key to our 2013-2014 project to "Eliminate MBD" from captive collections.
so have a think about the wild and how the animal behaves and try to re-create that. we then open up the next big question....Diet and are teh current offerings in the trade effective at all????
John Courteney-Smith MRSB.
Arcadia Reptile; Head of Science and Innovation
BRAND NEW BOOK out now. The Elements series; Part 1- FIRE, The Sun, its Use and Replication in Reptile Keeping
Find us on facebook under "Arcadia reptile"