Protection of the Grass Snake (Natrix natrix) by laying out Egg-Deposition Substrates
During the past decades, the
natural places for egg-deposition of the grass snake, apart from many other
structures, were reduced by mechanization and the intensification of agriculture
and forestry followed by re-allocation and consolidation of arable land.
A study in the area Wuppertal, Mettmann and Solingen
established that the majority of the known places for egg-deposition are horse
dung-heaps mixed with straw or sawdust. After laying out a large horse dung-heap
in Neandertal (district Mettmann), approx. 62 eggs were found during the
following activity period, and only two years later approx. 400 eggs were found.
The grass snake uses the fermentation heat of the substrate not
only for depositing eggs. The female snake stays there sometimes over weeks
before the deposition of eggs. The snakes also spend longer periods of bad
weather in the heaps and some use the substrates for hibernation. Nevertheless,
laying out new horse dung-heaps does not go without problems, since an
eutrophication of the surrounding area occurs due to the dung. Therefore, an
approval of the responsible authorities is required. A study carried out in the
Netherlands (Zuiderwijk, A. et al., 1993) with 72 artificial heaps, of which 45
were used as egg-deposition spots by the grass snake, resulted in the following
Large heaps are more suitable than smaller ones.
The material to be used should come from the direct
surrounding of the heap: dung-heaps near farms, leaf heaps in parks or forest
areas, compost heaps arround public or private gardens, reed heaps in larger
reed areas etc. It is favourable to mix the material well with branches and
limbs (Zuiderwijk, A. et al. ,1993).
Whereas Zuiderwijk, A. et al.  writes that the heaps should be removed and layed out anew after two years, the author has made the experience that it is absolutely sufficient to keep the volume constant by filling it up annually. This should be done during the months of April and May in order to reduce the effects on the grass snake to a minimum.
Zuiderwijk, A., G. Smit & H. van den Bogert . Die Anlage künstlicher Eiablageplätze: Eine einfache Möglichkeit zum Schutz der Ringelnatter (Natrix natrix L. 1758). - In: Gruschwitz, Kornacker, Podloucky, Völkl & Waitzmann (Hrsg): Mertensiella, Bd.3, Verbreitung, Ökologie und Schutz der Schlangen Deutschlands und angrenzender Gebiete, S.227-234, Bonn.