RAUK - Archived Forum - an experiment...

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

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.

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.

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?

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.

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.

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