A pilot study investigates differences in detection probability of common lizards and slow-worms at a nature reserve in Peterborough when using two different types of refugia.
One of the most common ways to survey for reptiles and amphibians is to use artificial refugia (also known as coverboards). These are simply cut out squares of roofing felt, plywood, tin or any other material that can hold warmth and/or humidity. These refugia attract the animals by providing a shelter, a warm place for cold blooded animals to raise body temperature up and providing food, as they also attract invertebrates.
Roofing felt is probably the most commonly used material for artificial refugia, due to it being inexpensive, easy to cut and light to transport. Furthermore, they are often considered less of a target for disturbance or vandalism. However, both anecdotally and in some studies, it has been suggested that some types of surveying materials are better than others for attracting reptiles.
This small study compared the presence of common lizards and slow-worms found under roofing felt and a corrugated material called CRS (with the trade name bitumen). The materials were cut into 50cm squared pieces and were laid in alternating grids of 4 x 5 in 6 different areas in the joint nature reserve of Collyweston Great Wood and Eastern Hornstocks between June to August 2013. They were monitored 3-6 times a week in both mornings and afternoons.
41 common lizards and 102 slow-worms were found during the study. Adult slow-worms and common lizards appeared to have a statistically significant preference for CRS, whereas juvenile slow-worms appeared to prefer roofing felt. Though any attempts at guessing why are purely conjectural, it is possible that the smaller body size of juvenile slow-worms means that they are able to warm up more efficiently against a flat surface, alternatively, they may be avoiding other larger reptiles which could predate on them. The common lizards and adult slow-worms may use the corrugated material as it is easier to access the underside of the refugia. It is important to note that though the majority of common lizards were found sitting on, rather than under the refugia, they still showed a preference for bitumen. Common lizards are alert animals and one could suppose that the harder more upright position of the CRS made for a better look out than the flatter, softer roofing felt.
Finally, whilst measuring other variables throughout the study, it became apparent that juvenile slow-worms were more sensitive to disturbance than their other counterparts. Detection probability for this group decreased when more surveys were carried out.
To conclude, though the sample size was small, this study may have some interesting implications for detection probability when planning reptile surveys.
(Alexia Fish, London Dragon Finder Ecologist)
Affiliated with the University of Aberdeen and sponsored by The Sir Maitland Mackie Scholarship for Environmental and Rural Land Use and the Amphibian and Reptile Group UK Grant.
Fish, A. C. M. 2016. Observations on felt and corrugated roof sheeting as materials for constructing coverboards to assess slow worm (Anguis fragilis) and common lizard (Zootoca vivipara) populations. The Herpetological Bulletin. No. 135, pp. 4-6