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will
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Posted: 09 May 2009
Decided to do a sort of experiment today; nice weather for surveying - 16 deg C and sunny, so I went back to one of my favourite heathland sites and set myself the challenge of spending 5hrs surveying one (productive) Ha of sand lizard habitat to see what I could find.  In brief:

the 'common' lizards were the sandies - I saw 44 in total (being careful not to re-count individuals given that I was re-walking the same transects within the Ha during the 5 hrs).  Most were males (about 30, with 10 females and 4 babies from last year, juvs).  Makes you wish that there was more heathland left, given the densities of sandies in the right habitat.  Males and females were not interacting, some females clearly gravid already.  Only 2 loose 'pairs' seen along the same stretch of heather.

Also saw 3 viviparous lizards and 1 adder - all in the wetter habitat at the base of the slope within the survey area, and one grass snake in the dry heather, more surprisingly.  The sandies could be found in the humid places as well as the more dry heath.

One of the males was an unusual turquoise colour, see pic alongside a more normal one for comparison.

Also saw one male sandy basking within 30cm of a male adder - would have made a nice pic but I disturbed the adder before I could take it.  Maybe luckily for the sand lizard !

Anyone familiar with the technique of repeated walks within a set area and a set time for reptile surveying ?  I know the usual methodology is to fix the transects and walk them once, rather than to fix a time and walk the same area again and again.  Anyway, I was surprised at just how much more abundant / visible the sand lizards were than any other reptiles.

Cheers

Will

Pics 'survey area' 'typical sand lizard' and 'turquoise lizard' below:







Vicar
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Posted: 10 May 2009
Hi Will,

DICE are looking at time-driven surveys for a 1km grid, supporting NARRS.

It's clearly a trade-off. 5 hrs on one hectare will yield more counts, but the area covered (say on a county basis) would be dramatically reduced, as survey 'hours' are a limited resource.

IMO It's 'horses for courses' and depends entirely on the objectives for the survey.


Steve Langham - Chairman    
Surrey Amphibian & Reptile Group (SARG).
will
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Posted: 10 May 2009
Thanks for the info Steve; I agree.  I guess it shows that with animals like sand lizards it's populations rather than numbers per se which counts 
herpetologic2
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Posted: 10 May 2009


How did you make sure you were not recounting
individuals which were already spotted? was that just
based on memory or did you photo id them in the field?



J
Vice Chair of ARG UK - self employed consultant -
visit ARG UK & Alresford Wildlife
herpetologic2
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Posted: 10 May 2009
The abundance of sand lizards over the viviparous
lizards possibly backs up the idea that dry heathland
isn't that great a habitat for the widespread reptiles.

The influence of the timing of surveys would have
dramatic effects on the detectability of the different
species. The adder is more readily found in the late
winter and early spring - emergence and mating - once
this is over the animals are harder to find -

Do you think that population estimates on summer survey
data for adders is useful? Do summer counts provide an
accurate reflection of the relative population size?

J
Vice Chair of ARG UK - self employed consultant -
visit ARG UK & Alresford Wildlife
mikebrown
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Posted: 10 May 2009

Hi Will

That is an an excellent result, more than we have managed to achieve in Merseyside in that amount of time with a group of observers in different places!

Nonetheless, it proves the value of walking round the same area several times. It is surprising how many extra lizards are recorded with this method. The problem is that the weather rarely remains suitable for a whole five hour period. It either becomes too hot or clouds over!

That turquoise male is really attractive!

Cheers

Mike


Mike Brown
Merseyside ARG
Vicar
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Posted: 10 May 2009
Some interesting views here John.

"backs up the idea that dry heathland isn't that great a habitat for the widespread reptiles. "

I wouldn't say that it isn't good habitat, but agree there are better habitats. It is true that when you have well-established colonies of Smooth snake or Sand lizard at a foci, they are the dominant species.

"The adder is more readily found in the late winter and early spring - emergence and mating - once this is over the animals are harder to find"

Our records suggest the opposite. When adders are concentrated at hibernacula sites, they (obviously) are more concentrated, hence the chance of finding them is less (unless you happen to stumble across such a site, where they are very obvious). A good field surveyor is more likely to come across adders once they have dispersed, as you get hits at hibernacula areas AND at migration areas (and in between).

"Do you think that population estimates on summer survey
data for adders is useful?"

Pop estimates - No (too complex)
Survey - Yes essential! - If we aim to protect adder sites, then clearly hibernacula areas are highest priority. Second highest (IMO) are the summer hunting grounds and the migration routes between hibernacula (plural) and these hunting grounds. I believe this interaction is how adders obtain genetic diversity, so in the long term, isolation to hibernation sites would reduce population fitness.






Steve Langham - Chairman    
Surrey Amphibian & Reptile Group (SARG).
will
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Posted: 11 May 2009

Thanks for your comments Mike; it only goes to show that your Merseyside lizards are much more thinly spread (even at foci) I guess, than Dorset lizards.  I was also lucky with the weather, which was ideal for the whole 5 hrs, not common as you say !

Jon - yes, I was careful not to re-count individuals and used photography whenever possible (long lens, no disturbance).  I agree also that reptile surveying is season-dependent for each species.  We all tend to focus on different species as the spring warms up.  Adders are perhaps similar to sand lizards in the importance of finding foci (eg hibernacula for adders, and core areas for sand lizards) at certain times of year.  I would agree with Steve that for population estimates concentrating on hibernacula at the start and end of the active season is best, but that establishing areas of summer occupancy and migration routes where applicable is also vital.

 


herpetologic2
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Posted: 11 May 2009
I was thinking of the numerous ecological surveys which
proclaim that the snakes found within the survey are
only low or small in status when in fact I don't think
that you can make any assessment of the population
status from sightings in the summer months.

Hibernacula for adders are relatively easy to find when
considering the likely habitat they will use for this.

Adders are described as 'generalists' in terms of the
habitat they use - woodland, grassland, scrub, etc. The
snakes are not uniformly distributed within the
environment. In the spring they are in small areas of
the available habitat - which are 'foci' or their
overwintering habitats.

In the summer they are often widely distributed along
migration routes and within summer feeding grounds.

However studies have shown that adders will adapt to
their surroundings if their habitat is reduced.
Populations on road verges tend not to venture far from
the road verge. While on more natural habitats they move
many hundreds of metres to their foraging areas.

Just another side to this I once carried out a newt
survey last year when I surveyed a pond at 10pm - count
of adult newts were 29. We went out again at midnight
and the count was 63. I don't think that many people do
repeated surveys in the same night on newt surveys. i
suppose that the population assessment would be the same
a medium population lol

J
Vice Chair of ARG UK - self employed consultant -
visit ARG UK & Alresford Wildlife
GemmaJF
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Posted: 19 Sep 2009

I think you are both right, Jon from the consultancy aspect where detection can be very low for adder unless 'foci' are targeted, Steve on a longer term survey without time constraints or covering a wider area of habitat than a potential development site.

Adder have a generally low population density, it takes time for them to intercept ACO and many consultancy based surveys just simply 'miss' the bulk of the population and so only detect presence at low numbers if at all. It isn't a good picture of the real situation. It takes far more effort than the usual 7 visits to achieve anything like a population estimate.

Steve with longer-term survey or more widespread targeting will see a completely different picture of adder populations. I certainly find the dispersal and the migration to the summer feeding grounds a great time for seeing adder, but particularly when I already know where to target my effort. That tends to mean there was a lot of 'down time' trudging around for days seeing nothing at all in past seasons until I stumbled across where everyone had got to!

Hence once you know an adder population(s) you can find animals at any time during the active season. If you don't know the population there isn't usually the time available in the world of consultancy in my opinion to really formulate a picture and check all suitable habitat over a wide off-site range.

For such work at a new site, I agree with Jon that I can't make an assessment just from summer sightings or un-targeted spring survey, in such cases I've relied on past knowledge to locate suitable 'foci' and likely important areas and base assessments for capture effort etc from that. So far I've not got it wrong, on two projects I detected adder presence on the extends of the site yet felt the works would not impact the adder populations and that is exactly how it turned out with not a single adder showing up during the mitigation works, yet I knew exactly where to find them each day just a few meters behind the exclusion fence. I guess that is the pay off for spending half my childhood working out where I did and didn't see adders.

Interestingly I now know of 4 populations where the summer feeding grounds and the hibernation area are within a few meters of each other. I agree therefore with Jon that they act as generalists, given suitable habitat, they don't actually migrate at all as they simply don't have to, though if needed they will and those habitats can be variable.

GemmaJF40075.984837963
Gemma Fairchild, Independent Ecological Consultant
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Posted: 20 Sep 2009
[QUOTE=GemmaJF]I agree therefore with Jon that they act as generalists, given suitable habitat, they don't actually migrate at all as they simply don't have to.[/QUOTE]

I've often wondered...whether this was partly an evolutionary trait such that the males don't compete with females for the food chain in lean years.

Or, to put it another way...why are the males (and some non-reproducing females) the ones who migrate...why not the gravid females?

Also I think the migration serves the useful purpose of juveniles 'mixing' and 'swapping' clans to strengthen the gene pool.

I've got a sneaking suspicion that adder demonstrate neophobia to refugia more than other species (I always thought this of Smooth snakes until this year...record year for expanding the known range for Ca using new tins). I'll check the stats sometime to see how long it takes different species to start using refugia...but there are a lot of biases to consider.

Steve Langham - Chairman    
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GemmaJF
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Posted: 20 Sep 2009

I don't think it is neophobia, though I once would have said that. I now think it is simply there are less snakes in a given population so that interception and thus adoption of ACO occurs at a low rate also there is less chance of lifting the tin at just the right time for the animal to be using it as there are simply less animals compared to say if Common Lizard or Slow-worm were the target species.

What changed my view? I once had to mitigate an adder feeding area. .

One week of ACO being placed at very high density and I started the capture works. We had all four widespread species and day one saw 5 adult adder picked straight off the top of the ACOs where they were openly basking in full view at 08:00 - the ACO having been placed for just 7 days before the first check. So here we have a relatively high density concentration of ACO and snakes and quick adoption of ACO.

I have seen the exact opposite with more usual survey type densities of ACO, adult adder not being detected for an entire season comes to mind at one site in Kent Lee will remember (we did get one neo in the first season). The same with a grass snake population that I did a voluntary survey for in Essex, tins being put down for a season with no detection, then the numbers built in the second season (by this time I had already intercepted a huge number of individuals simply by sight).

Now compare this to day two of one mitigation I did and the only adult grass snake to be captured on the whole site was under an ACO placed for the first time the day before. Again this was my usual high density spread I use for capture works at 5 pace intervals. Proof in my mind that if a snake detects an ACO it has no fear of using it simply because it is new.

So previously I considered they just didn't 'like' newly laid tins and my low ACO density survey experiences seemed to confirm that, but my experiences with consultancy work changed my view.

Not very scientific I know, but enough to convince me that detection of the ACO is the issue, not a dislike of them being 'new'.

I would though say that generally I like a 'settling' period of a couple of weeks for ACO, I don't think these days this has anything to do with the likelyhood of use, (I'm forever laying felts and walking back along them picking off lizards a couple of hours later) I simply find the flat bed that forms makes it easier to see the animals!

Just one more interesting observation, I once put a high density of ACO around an adder hibernation complex. Not one was ever used by anything but neos yet I could count adult animals on any given day with suitable weather. For some reason, they just don't seem to bother with them near the hibernation site. My theory, the hibernation site already serves them very well for their purposes and most snakes seem to only use ACO whilst in the process of speeding up a metabolic process such as shedding or digesting. Perhaps there is no need to seek the extra heat of an ACO at the well established hibernation site as it is already fairly ideal?

GemmaJF40076.0280208333
Gemma Fairchild, Independent Ecological Consultant
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Posted: 20 Sep 2009
Thanks Gemma, and you could be absolutely right!

Is there any chance that a high density of refugia denied usual basking sites? - presumably you lay felts in areas more likely to be used by the reptiles than on lush vegetation?

I've been meaning to put together an 'encounter probability' model for years now....one day I'll have the time (but probably not the data).

Steve Langham - Chairman    
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GemmaJF
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Posted: 20 Sep 2009

I did an update of the last post there Steve.

Generaly Steve a lot of mitigation sites I've covered were pretty uniform grasslands, often with no obvious basking sites other than a raised bank or ditch bank type of feature. It's pretty much a case of uniform cover on this sort of site, though usually the ACOs placed in an obvious sun trap or on a sunny bank will be the first to produce.

I think it is fair to presume at say 5 pace intervals that the ACO do not actually deprive of any basking site, though they may lay on part of it, there are plenty of gaps in between unaffected but the presence of the ACO itself.

GemmaJF40076.0331018519
Gemma Fairchild, Independent Ecological Consultant
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Posted: 20 Sep 2009
Just to add some supporting data that adders are thin on the ground...at least in terms of density.

From the formal reptile surveys this year...we have had the same number of Smooth snakes reported as Adder (to within 1%), across ~40 sites, only 8 of which support Ca!, and about 30 support Vb.

As Tony always says...when Ca are present, they can occur in very respectable densities.

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GemmaJF
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Posted: 20 Sep 2009

Though having just had a good think about it Steve, I can identify something in these situation that could have deprived the animals of natural basking sites - exclusion fencing.

The usual idea being that it is used to surround your capture area whilst one works at capturing out the site.

I could be 90% certain that those adders would have in the absence of exclusion fencing actually have used their hibernation bank first thing in the morning, for this is one of the sites where it was only a few metres away, if it wasn't for the fact they couldn't get to it because of exclusion fencing. I often intercepted animals not caught up in the mitigation in that area in the morning whilst releasing those that were.

So that puts a different slant on things. I do hate you sometimes Steve, I just think I have it all figured out and you go and throw a spanner in the works and get me wondering about it all again  

The same with that grass snake, it would normally have had access to higher roadside banks which caught the early morning sun, but not with the exclusion fencing in place.


Gemma Fairchild, Independent Ecological Consultant
Vicar
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Posted: 20 Sep 2009
heh...anybody who says they have this all figured out is lying 

Every trip out slaps me in the face with how little I still know...I just get better at asking questions.

Steve Langham - Chairman    
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Posted: 20 Sep 2009

Too true Steve, most of the fun is that it is always a case that I end up with more questions than answers.

 


Gemma Fairchild, Independent Ecological Consultant
Chris Monk
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Posted: 20 Sep 2009
Gemma
I can back you up on adders not using ACO's around hibernation areas. The Peak Park, advised by Howard Inns put out tins in their 1994 adder survey. The tins were close to where estate staff and rangers had regularly seen adders. There were two years of surveys with regular visits from spring to autumn and no adders were ever found on or under the tins although many were seen nearby.
When I restarted surveys in 2005 I found some of the tins still in position and guess what - they are still not being used by adders, although apart from one where the habitat has changed, adders are still close by. In fact on a field trip with John Newton and the Sorby Society this spring, we found another tin further up a valley than we had been before. Sure enough about 20 metres away was a group of adders and a few weeks later there were a whole load of sloughs in the heather and bracken all round the area.

Chris
Derbyshire Amphibian & Reptile Group
www.derbyshirearg.co.uk
will
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Posted: 06 Jun 2010
Anyone got any sandy news or pics ? it's been a quiet season for them on the forum so far this year.  I tried to repeat my experiment from last year (see above) a couple of weeks ago and only saw around a dozen animals rather than the tens I had last year (admittedly the weather wasn't quite so good) - have others found it harder to find sandies this year ?  Any news from the North on the wonderful Merseyside sandies ?  Anyway, here's a couple from the transect site from this year:





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