RAUK - Archived Forum - Grass snake egg laying sites

Hi all,

The subject of grass snake egg laying sites has come up on a couple of threads so I thought I would start off a discussion on what makes a good egg laying site.

Firstly, we all know I guess that compost heaps are good. Garden ones in particular. Now I would raise the question is any old compost heap good? If you make a heap of dry grass cuttings are they likely to heat up at all? I'm thinking of a site I know where grassies are abundant and the management team put in some artificial egg laying sites. Never once have I recorded a hatchling grassie anywhere near these heaps. I think this is because they don't produce any significant heat.

Gardeners know there are two types of compost heap. Heat compost heaps and worm compost heaps. A heat compost heap steams like hell, has a good mixture of grass cuttings and bark to give a phosphorous/nitrogen balance and cooks up a treat. A worm heap is a different beast, doesn't get hot and relies on worms to do all the work.

I would argue that the former sounds good for grassie eggs, the later not so good. I assume that before man started to change the environment that the prime egg laying site would have been rotting marginal vegetation on flood plains. Nice and damp, in full sun and getting very hot, or perhaps fallen trees in a similar environment.

Now to the point. A good heat producing compost heap needs maintenance. You have to water them occasionally if they are open to the elements (rather than in an enclosed plastic bin) to keep everything going. They also need to be topped up regularly with new material as they compost quickly. So are these really suitable outside of the garden environment where they may not be maintained?

I know a German study used manure heaps placed in the wider countryside to see if they were useful to grass snake conservation. These have all the qualities of a good heat producing garden compost heap but don't need maintenance. (70% of the heaps placed were used by grass snakes)

Just thought it would be interesting to get others opinions as I have seen a few examples where compost heaps have been put in with the best intentions but in my opinion they wouldn't have attracted grass snakes at all as they were not well designed as self maintaining heat producing heaps.

Hi Gemma

When the airfield at heathrow is bottomed-out it is joined together with any other green waste including wood chip from our arb team, and is composted at a special designated site.  Here we have a teagle which turns the compost at regular intervals and thus the process is very rapid and very hot û too hot perhaps for the snakes.  However, I'm lucky in that I'm able to steel some of the ingredients for use on nature reserves specifically for grass snakes.  Generally the grass cuttings are green and provided that the heap is large enough (in my case a good 10-12 ft high) there is always heat coming from it during the breeding season.  I also have large piles (several tons worth) of woodchip which can often be seen steaming away.  Both piles are simply topped up each year.  Neither seem to dry out particularly and in fact the grass heap is rotted down so well that it is still very moist - if you can use green grass in the first place this helps.  I think on sites where continuous management is not always possible size and green material would be the key components, although I appreciate that not everyone will have the same resourcesà

I've wondered this too - Ive read that rotting logs are used in natural situations but its hard to imagine these as being anywhere near as effective as compost heaps in generating heat.  I guess rotting marginal vegetation would include the large litter layer that develops in Phragmities reed beds...

All,

I have seen three egg laying sites in EF. One was "made" albeit inadvertently by forest volunteers piling anything from old bracken, wood shavings/chippings, birch saplings and grass/leaf litter into a heap (remembering that below all this was a good layer of moss growth), but, the two natural ones are/were suprising choices for GS when it had a number of options available anyway. The first (and I have seen hatchlings/neos emerge from them are the stumps of fallen trees that have rotted on the inside but retain shape from the unsopported bark!

The third location where I have seen a gravid female await ovulation and lay eggs was quite simply in the sphagnum moss growing within banks of mature heather. This can get quite deep, up to 300mm in places and although some areas attract mice/vole runs, even on a cool evening, these can feel really warm inside to the touch.

Some lakes/ponds which have bull rushes (no latin here I'm afraid) again the moss feels damp in places but warm in others and I have seen plenty of GS awaiting ovulation here esp late in the evening.

There you go, thats about as much as i can give you. R 

 
The dry cuttings actually dropped in temp with depth initially, presumably because it was acting to shade and the decomposition is so slow that it can not compensate.  The green area however at 10cm was already on average 36.5^oC rising to almost 60^oC by 40cm.  As you can see this pile is also quite shady.  The green material was still moist and not hard so could easily be burrowed into.  I have found this exercise quite useful - I was always told size is important but perhaps other factors have more influence.  Green material, and grass if possible, seems to produce much more favourable conditions.  Of course sites will vary as will materilas used and specific locations, aspect, age of material (the dry cuttings are recent) etc etc.  Any comments welcome!

What an interesting study Rhys. Perhaps some shade is no bad thing if there is a lot of internal heat coming from decomposition. It seems from some of the replies here that certain sites will rely on sun warmth during the day and retained warmth at night and there will not be much heat from decomposition. In a wet season might some of these sites suffer from lack of incubating heat?

Do people think that providing egg laying sites, like heaps of vegetation or woodchips, for grass snakes improves their numbers (all other factors being favourable) or will they just find a place like those mentioned here that we would not think of as being optimum and do just as well? As Gemma says to keep the heat up in a heap requires attention on a garden scale but is such work needed on conservation heaps? Manure heaps sound good but would reserves etc. be prepared to cart the stuff in (and possibly upset folk with the initial smell)? There could also be problems of enrichment which might be unwelcome on heaths etc.

 I work on a farm and we have muck heaps situated around our fields all year round, i've noticed that grass snakes not only visit these sites for egg laying but they find them really usefull for removing old skins as i'm often finding sloughs dotted about, i would also imagine (particully the young) find hunting good here. I have a question to put out to any body with any info. Do g,s or any other reptile use heaps to hibernate in? If so would adding muck/old hey ect durring the winter months have any ill affects?

                  Thanks,lucym

Lucy

I am sure that adding material wouldnt actually harm any reptile as they would still be able to burrow back out again - make sure the new material is well broken up so that animals can move around in it -

Regards

JC

Whereabouts is your farm?

I agree with JC, the adding of new material is likely to be of benefit by keeping the heap active. It is probably the process of new material being added all the time that makes these real world muck heaps attractive to grass snakes.

I'm not sure if grass snakes hibernate in muck heaps or just seek them out to lay eggs. I've only seen them emerge from hibernation from earth banks and the like and I know females can migrate some distance from hibernacula to favourite egg lying sites.

Maybe you can keep an eye out for them on the farm Lucy this spring and let us know if they are emerging from the heaps during March or just visiting them for egg laying later on in the year? If those sloughed skins start to show up early in the season I guess we could be fairly sure they do use the heaps for hibernation.

Thanks for the replies, all added material is broken and loose so i wont stress to much about blocking any body in then, the farm i work at is on the surrey/sussex border not to many miles from Guildford. I'm aware of forum regs so you'l appreciate i cant offer exact co-ordinates,

                               lucym