RAUK - Archived Forum - Refugia Survey

Does anybody have any guidance on the appropriate spacing of refugia on uniform heathland ?

Aim of the survey is to determine the presence of species, not population densities.

Each site would be approx 25 hectares with a perimeter of around 2000m.

Apart from the usual issues of placement, permissions and situation away from the public gaze, I can't find any work on 'optimal' spacing of tins on uniform terrain.

16 tins over this area would give me about 100m separation - roughly.

All comments gladly received.

Steve,

16 tins would be a little low in my guestimation for a 60 acre site even for presence absence. I would suggest 30 would be nearer the mark. Multiples of five also make analysis easier later on. In particular if you have a fairly featureless area it is more difficult to optimise a presence/absence study, compared to a site with obvious margins, banks, etc so you may want to compensate by going for even more tins.

Lee,

Doesn't the Froglife guidline of no more than 10 tins per hectare relate to relative population estimates, not presence/likely absence studies?

Yep see your point Lee.

Steve, I think what Lee and I are both getting at is that one wouldn't evenly distribute the tins across the site with uniform spacing but would be more likely to bunch them in likely positions.

With a density of 10 per hectare you could reasonable cover the entire site with tins at even spacing. With a much lower density you have to optimise to where animals are 'likely' to use the refugia.

Lee pretty much taught me how to place refugia and I would recommend it is worth getting out to a site with an experienced recorded and seeing how refugia survey is set-up before going it alone. It takes a little experience to realise that what appears to be fairly uniform habitat to our eyes is featured to a reptile sometimes!

OOps, I must have been typing as Gemma was :P

Basically I'm writing up a proposal/plan over the winter, with an aim of having a final draft by Xmas, which gives me the new year to co-ordinate with the various bodies/orgs.

Having started to write it up, its already looking quite the daunting prospect !, but there is a logic to the scale, driven by the goals. Having said that, even if nothing comes of the plan, I'm already finding it of vital experience.

Part of the process would involve what I call IPB, but basically inteligence preparation, site survey, identifying likely micro-habitat, extant records etc.

What would be REALLY helpful, would be a look over of what I am proposing (plan review) by persons far more experienced than myself (not too hard to find :P). Doubt I'll have a first draft ready until the end of the month tho.

Unfortunatley Steve 'Saliha's' post is nothing more than a very thin veil for the advertising in their signature.

The passage is a copy and paste from the NARRS site:

http://www.narrs.org.uk/widespreadreptile.htm

Now Saliha, do the right thing and waste somebody elses band width.

Steve do you have the data for how many animals per hectare are recorded on average for each of the widespread species using this survey protocol?

It would be interesting to compare to a cluster survey based on the old 'I know it's good habitat because I've been doing this for years and have no trouble finding animals' approach. Having said that we survey at much higher density than 1 refuge per hectare usually, and few sites I've worked on were uniform enough for a simple grid. (too many woodland areas, roads in the way etc). To date what info I had on using grids indicates for reptiles the results were poor.

One of the advantages I've found of say putting out a loose group of five refugia is that on any given day/time of day one may have the advantage over another. Where as one might be prone to shading for part of the day etc. (a simple example is a loose group of five refugia in our back garden, any one of the five will produce Zv, 2 produce Af, but only one ever produces juvenile grass snakes, the hottest one, on a low south facing bank). Note this is an area about 30ft x 20ft but still the placement is critical for one widespread species. It's also the one least often used by the Zv!

I did figure once I could comfortably check 200 refugia in an hour, including stopping to record details, just trying to work this in the context of a consultancy style presence/absence exercise where to be honest the time put into visual suvey (other than for adder) tends to be far less productive (though none the less interesting) than checking refugia.

Just to add, regarding the reinforcement of 'good habitat', I  have data of site clearances (where regardless of initial survey the whole area was covered in a uniform grid five paces apart each way) clearly showing the highest density of animals came from the original survey positions. This gives me a dilema, either I actually am good at spotting good reptile habitat, or does placing refugia for initial surveys actually attract animals to, or compel them to stay in those areas  I'm certainly now in the habit of concentrating presence/absence surveys around mitigation areas whenever possible (i.e. to survey in adjacent similar habitats) and also very reluctant to keep refugia down longer than needed to get my base data in an area that will eventually be subject to capture works.