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egg laying sites

Printed From: Reptiles and Amphibians of the UK
Category: Herpetofauna Native to the UK
Forum Name: Grass Snake
Forum Description: Forum for all issues concerning Natrix natrix
Printed Date: 28 Oct 2020 at 8:54am
Software Version: Web Wiz Forums 11.06 -

Topic: egg laying sites
Posted By: will
Subject: egg laying sites
Date Posted: 05 Jun 2015 at 8:52am
This question is prompted by a friend of mine who sent me a photo of a grass snake egg laying site in the bowl of a tree which was discovered by accident.

It made me think - where do grass snakes actually lay their eggs? we know they use compost heaps etc but there's a big element of 'observer bias' here - that's where we think they lay their eggs, and sure enough, that's where we find them when we look.

But what proportion of grass snakes 'out there' in the wild use other more 'natural' places? How could you find these sites in an unbiased way? it's very hard to track grass snakes, as we all know. So maybe you would have to use a tracking device placed on female snakes before they lay their eggs, and follow them to see where they lay. Has anyone done this sort of research, I wonder?

Posted By: Suzy
Date Posted: 05 Jun 2015 at 10:44am
Presumably they also choose somewhere where the decomposing vegetation is producing heat. Or will a heap of anything that is in full sun do? I am thinking of river/streamside piles of vegetation formed by high water after heavy rain. These can be quite substantial but some seem to dry out quite quickly. Again can they judge whether a place will be liable to being washed away as too near the water? Do grass snakes scope places out the year before? Or do they just move about pre egg laying and find somewhere, bearing in mind that somewhere suitable the year before might no longer be so or might have disappeared altogether.
Not answering your questions Will, but plenty to think about.


Posted By: will
Date Posted: 05 Jun 2015 at 11:27am
all good questions Suz, not sure anyone has done detailed research, and much of what we read is anecdotal only. Historical sites are used generation after generation - do the hatchlings carry some memory of their place of hatching? With telemetry getting more feasible all the time hopefully someone will be able to answer some of these Qs...

Posted By: AGILIS
Date Posted: 08 Jun 2015 at 6:27am
Funny I have not come across their egg hatching places since being a late teenager when there was more habitat about and you used here about the odd finds reported by people finding them on allotments among the compost heaps keith🐉


Posted By: Robert V
Date Posted: 13 Jun 2015 at 6:50am
Hi Will,

maybe anecdotal, maybe not; but I have seen hatchlings emerge and found eggs in rotting stumps of old trees as well as in the frass inside rotting stumps that are still erect. Tony mentioned many moons ago that he knew of large areas of moss that were favoured as egg laying sites, and, as Suzy mentioned, any natural / semi natural build up of vegetation in piles could be suitable if in full sun.



Posted By: will
Date Posted: 13 Jun 2015 at 6:00pm
Thanks Keith and Rob - your anecdotal observations tally with mine.  I can only find one paper that features radiotracking of grassies, and it goes back to 1984, with a sample of only 4 females.  Time for some new research maybe?  I'm guessing that the transponders have got smaller and cheaper (they had some adders with tracking devices on Springwatch that looked quite small - though I think they used white tape to attach them, which would have helped the buzzards to find the adders much more easily Confused...)

Posted By: Robert V
Date Posted: 13 Jun 2015 at 6:33pm
Hi Will,

it did tickle me what you said about the transponders being cheaper and smaller - take a look at the type of suggestions going on in the study in Jersey - go on facebook, look up naturalists - natrix / grass snakes and see Rob ward's post - he's doing a tracking exercise, but now talking about sewing on transponders through the scales, and / or sticking them on with duct tape!

There's nothing quite like the old school time and effort in patiently watching and waiting to unravel the mysteries. It took me weeks of watching, checking, checking again, gently poking to see if eggs were still there, then one day, after I'd missed lots of them hatch and make off  I got this... Ok, it wouldn't win any awards, but it shows a hatchling / neo finally emerging from the egg laying site...


Posted By: Robert V
Date Posted: 13 Jun 2015 at 6:38pm
Slightly closer :-)


Posted By: will
Date Posted: 14 Jun 2015 at 9:41am
fantastic observation Rob, I guess I was hoping there would be a lazier option available to me for locating Nn egg laying sitesWink  

Posted By: Iowarth
Date Posted: 15 Jun 2015 at 11:38am
Excellent Rob. I think that people sometimes overlook the fact that grassies were probably finding natural egg laying sites such as this long before man-made compost heaps even existed!

All the best

Chris Davis, Site Administrator

Co-ordinator, Sand Lizard Captive Breeding Programme (RETIRED)

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