https://www.researchgate.net/profile/Angelo_Pernetta3

Contact Angelo - he will give you good advice on this topic.

Good luck!

In short it will depend on the objectives of your study. What would you like to test? Presence absence? Relative abundance? Activity patterns? 

It is merely a presence or absence survey but I'd like to know population sizes if possible. It depends if I find anything, population estimates could always be carried out in the future. 

As stated by others; this varies - I would suggest a minimum of around 8 visits for presence/likely absence surveys (as Sewell et al 2013 suggest) more being better.  In terms of regularity, it's obviously best to visit in a variety of times and weather conditions during a variety of months - if the project allows, there tends to be a super abundance of reptiles in August-October time after they have hatched/been born and there are plenty of juveniles around; this can be the best time to locate reptiles at a site where there is a low relative abundance due to the temporary "high".

Additionally, it's best to leave a few weeks to a month for the ACOs to bed in and be discovered by the reptiles; after which they will generally be used daily if they are in a favourable condition and position.  (Speaking from experience of extensive Common lizard survey at least).  Probably best to spread the visits out over a longer period however to give the animals longer to discover the tiles - and the more visits the better the sample ultimately.

I have found that the time of day is a big factor. One may argue to check mats early as they provide shelter for herps during the night (apparently providing prolonged warmth in to the early morning from the previous day). However, I have found that they provide the highest yield once the sun is up and has began warming the mats and drying out the dew and moisture. Doing this however you might tend to get more common lizards on top of the mat using the new-found warmth and they are tough to catch if this is the objective. During the hottest part of the day between ~1-3, especially using black/dark green roofing felt, you will find very little as the mats get roasting hot. This warmth can provide some results into the evening though as lizards return to the mats as the temp drops. Where they then go by the early morning, who knows!? I would imagine there is variation at each site, but after a few days surveying the site at different times of day you may start to get an idea of what is going on.

We have done a similar practice in sampling amphibians and reptiles in southern California. We placed numerous 8 x 4 sheets of ply-board throughout the habitats of interest the year prior to sampling. We had trained individuals inspect the ply-board at different times of day throughout the year, though morning was most common. Indeed, for certain reptilian taxa, it worked well (Crotalus helleri, Lampropeltis californiae, Pituophis catenifer), for others (Lampropeltis zonata), as we anticipated, it was flawed. I would never rely on this method as my only source of data.

Often the boards need to "season" for a year or two before they become productive.

A couple good references for North America:

McDiarmid, R. W., M. S. Foster, C. Guyer, J. W. Gibbons, and N. Chernoff (eds.). 2012. Reptile Biodiversity: Standard Methods for Inventory and Monitoring. Berkeley: University of California Press. 151-163 p.

Graeter, G. J., K. A. Buhlmann, L. R. Wilkinson, and J. W. Gibbons (eds.). 2013. Inventory and Monitoring: Recommended Techniques for Reptiles and Amphibians, with application to the United States and Canada.

Cheers guys, waiting for a few sources I have ordered to arrive in the post. Will pool all my resources when they arrive and hopefully write up a comprehensive methodology.

For reptilian survey, the best time to encounter the presence or absence is early morning, mid -day observations were not found suitable. That was I found suitable.

Moreover this also depend upon the type of species.

This guidance might be useful to you: http://www.narrs.org.uk/documents/Survey_protocols_for_the_British_herpetofauna.pdf

Last year on the Studland peninsula (Dorset), we usually checked refuges each week, from June (started too late!) through to November. In the height of summer the temperature got so warm so early that we rarely saw anything.

In conversation with an officer from the Amphibian and Reptile Conservation Trust it was suggested to me that some species (particularly adder) are sensitive to disturbance and will stop using a refuge if it is lifted too regularly.

Hope this helps a little.

You can look the studies from CEBC-CNRS (http://www.cebc.cnrs.fr/). There is several hundred concret' slab to collect snakes. Between May to September we try to catch (CMR program) as much as possible snakes.

The slab are grouped by "area" (track in loop shape if possible) and we try to pass on each area at least one time par week (more if possible).

From my experience, you have to put the slabs before the winter to optimise your probability to catch snakes under the slabs. The slab-shelter seem to need some time to attact (perhaps loose the "concret smell"), to be notticed.

There is some "good" time to catch snakes. Of course, the mornings are good specially in mid-summer when days are very hot. Just before and after storm you usually are very lucky.

HI Steven,

For my PhD on smooth snakes I utilised approximately 1,100 artificial refugia across multiple healthland sites in Dorset. My methodology was based on that proposed by Chris Reading in this paper. 

Checks were made on a weekly basis in appropriate field conditions. Higher frequencies of checking resulted in fewer captures suggesting disturbance became an issue.

Cheers,

Angelo 

http://www.jstor.org/discover/10.2307/2405294?sid=21106224183943&uid=2129816&uid=67&uid=5910784&uid=62&uid=2129760&uid=3&uid=3738032&uid=2