We
are therefore considering using Onduline or roofing felt in NARRS
reptile monitoring programmes, and we welcome further views on this.
If a light material is used (and costs were met), it might be reasonable
to expect surveyors to lay as many as 40 refugia. The most effective
size for refugia is another subject for examination, and whilst many
people use roughly 1x1m tins and sheets, smaller (and larger) sizes
are certainly effective. Among the participants, and from HCT survey
experience, small metal or Onduline refugia (approx 50x50cm or quarter
of a square metre) attract reptiles of any species. |
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As
it is not always safe or possible to use artificial refugia, a system
is needed for dealing with such occasions when permission is not forthcoming
or there are security concerns. At the workshops, it was felt that
if refugia could not be placed in the large majority of the areas
identified as good reptile habitat, then the square would have to
be abandoned and another one sought. Refugia ought to be spaced as
evenly as possible across the square (according to identified good
habitat), but if security concerns or permission problems prevented
survey in some areas, this would be a significant problem. If refugia
have to be somewhat clustered, this is not necessarily a problem.
The question is whether or not all the 'key areas' could be surveyed
using refugia. Key areas would be areas you would intuitively expect
to find reptiles; hotspots perhaps. They are areas that would significantly
increase rates of detection for the square, or might even be crucial
to finding a species at all, e.g. the only piece of adder habitat
(without which adder would not be detected). In order to make this
judgement, the initial assessment visit is necessary to identify (and
map) all reptile habitat, and identify the key areas to target with
refugia. After seeking permissions, each surveyor would have to make
a decision on whether sufficient key areas can be surveyed. Perhaps
a threshold of 80% would be an ideal minimum, but 50% might be more
realistic to minimise the number of aborted squares. |
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The
workshops and questionnaires generated some useful tips on identifying
landowners and obtaining permission efficiently. Asking around locally,
face-to-face contact, and posting notices in shops or through doors
were suggested as tried and tested methods. Passers-by, dogwalkers,
local residents and tradespeople often tend to know who owns the land
in an area. There is also a good chance that surveyors may be approached
by inquisitive passers-by who could help identify landowners, and
sometimes landowners themselves. Maps, signs and notice boards may
also give a clue to who landowners are. Workshop participants felt
that it was not thought wise to ask landowners for written or signed
permission from landowners, but that verbal agreement would be sufficient.
A friendly face and 'people skills' were identified as important factors
in winning over worried or suspicious landowners. Some generic guidance
would be useful on how to describe NARRS in favourable terms (and
the official introduction letter for landowners should be couched
in appropriate language). Surveyors should be well briefed in obtaining
permissions, and must confirm that they have received permissions
when they submit their results. |
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For
statistical analysis, it is important that surveys are as consistent
and comparable as possible; therefore we need ways of standardising
or correcting for differences in effort and chances of detection.
Skill levels differ between surveyors, and visual search data would
obviously reflect disparities between surveyors' skills. Emphasis
on refugia would help minimise these effects, but as visual search
data are valuable, we intend to collect these too, albeit within a
prescribed route protocol. Training could instruct surveyors about
suitable survey conditions, and multiple visits (3-5?) would reduce
variability further (and increase detection). |
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Clear
instructions would be needed on the timing of survey visits (season,
time of day, weather), and effective training on habitat recognition
and survey fieldcraft would be crucial. The workshop participants
thought it conceivable that the anticipation of checking refugia might
make some surveyors over-enthusiastic, in which case it might be wise
to cap the number of visits and direct their efforts to other survey
squares. |
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Other
effort-related variables need to be addressed; particularly time spent,
number of refugia used, distance walked and/or area covered. We have
received a range of views from the workshops and the questionnaires
received so far, generally suggesting that effort should be standardised
as much as possible through survey protocols. There are still good
arguments for permitting variation (and correcting for it later),
but standardisation is eminently preferable (despite some inevitable
variation). Standard protocols remove the need for post-hoc correction,
and there is some benefit in asking fixed levels of effort from surveyors
who might otherwise be put off by open-ended requirements. Also, if
survey time isn't limited to 2-3 hours, detectability can change dramatically
in relation to time of day and weather variation. We need to do some
trials over the coming months, but options for standardisation include:
a regular fixed route (tailored to good habitat), a standard number
of refugia, a limit on time spent, and a limit on distance walked.
We will probably discount area covered as a measure of effort, as
it is difficult to measure, and search intensity within any area is
difficult to standardise. |
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Refugia
ought to be distributed evenly in all areas of good habitat (or a
representative selection where habitat is extensive), such that they
can be checked on a fixed survey route (bearing this in mind when
laying them). Visual searching for reptiles is obviously an effective
way of increasing detection, and we intend to incorporate it into
the survey design. Visual search effort would need to be standardised
as much as possible, but following the refugia-checking route too
strictly would hamper its effectiveness. Straight-line transects (and
structured derivatives) may be a good way to survey reptiles along
linear features such as footpaths, but in wider habitat strips and
areas of open habitat it is too restrictive. It seems wise, therefore,
to allow a limited amount of deviation from a fixed route in order
to increase detection. A standard 'buffer' of perhaps 20m could be
set, with visual search permitted up to this distance on either side
of the route. As time constraints will be imposed on each survey visit,
this ought to leave little scope for wandering 'off-route' and should
not compromise standardisation. |
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Even
with strict protocols, a significant part of the decision-making would
be the responsibility of the surveyor however. Where the route does
not follow obvious 'hard' or linear features, the surveyor would need
to exercise discretion and be careful to stay within route. Once again
this highlights the need for good training and guidance, including
ecological notes and photo-guides on habitat preferences, and tips
for spotting reptiles and improving fieldcraft. |
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Over
the summer and autumn of 2006, volunteers are continuing with stage
2 of the pilot, trialling methods and protocols, and although we appreciate
that reptile survey is much more productive in the spring, we still
hope that some valuable findings will come out of this. You can download
the instructions and trial protocols that volunteers are following here. We also provided an
introduction letter that volunteers could present to landowners; you
can download this here. |
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Widespread
reptile pilot survey |
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Following
on from our initial consultations, we launched a widespread reptile
pilot survey in March. The first stage allocated 40 volunteers a random
1km square near to their homes, and required them to make an initial
assessment visit. The purpose was to explore some practical and logistical
aspects of survey design, such as: |
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Logistics of survey visits. | ||
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Identifying reptile habitat. | ||
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Obtaining permissions. | ||
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Suitability for refugia. | ||
Participants
completed a questionnaire on their experiences and findings. The feedback
was extremely useful. |
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The
squares appear to be fairly representative of the predominant land
covers in Britain, i.e. most squares contain agricultural land and
some squares are totally arable. They contain variable amounts of
urban and suburban land cover, forest, railways, grassland, scrub,
heath, moor and other semi-natural habitats. Most initial assessments
seem to have taken people 2-3 hours and were generally possible by
walking public footpaths. Where permissions were sought, these were
generally forthcoming after asking locally to identify landowners.
Some surveyors asked about permission to lay refugia in the future,
and received a generally positive response. A standard letter would evidently smooth
the way however. Judging by the squares surveyed so far, a walk of
2-8 kilometres would be necessary to identify all, or nearly all,
areas of good reptile habitat. Livestock and public access were recurrent
issues for concern, but most squares had sufficient areas of good
habitat to lay refugia safely. |
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Surveyors
estimated the percentage of land cover that would support each of
four widespread species (common lizard, slow-worm, grass snake, adder).
From the assessments received so far, mean percentages for each species
were 20, 18, 17, 13% respectively, with ranges of 5-75, 0-70, 0-60,
0-70% respectively. Three squares were reckoned to contain no adder
habitat, and one square each for slow-worm and grass snake had no
habitat (the latter being upland habitat in Scotland). The mean cover
of reptile habitat irrespective of species was 17%, with a range of
3-41% (3-41 hectares). This assumes that surveyors are reasonably
adept at recognising reptile habitat for each species. Training must
ensure that this is adequately dealt with. |
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We
also held workshops in Derbyshire and Surrey in April, to 'brainstorm'
various survey issues. The discussion was lively and we thank all
those involved once again. |
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At the workshops,
we made the decision to use both refugia and visual search in NARRS
reptile surveys, and to standardise numbers of refugia. Although we
had previously been reluctant to rely on refugia because of security
concerns, we realised that the greatly increased detection made it
worth pursuing; and if there were insufficient places to safely lay
refugia, or permissions were not forthcoming, squares could be discarded
after the initial assessment visit (and another one selected). In
the pilots surveys, respondents' opinions varied widely on the number
of refugia thought necessary to sample a square adequately, from 15
to 700 (the latter based on 10 per hectare). The mean was 145 refugia
per square (or 69 refugia if the anomalous suggestion of 700 is discounted).
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Obviously
the logistics of laying and checking refugia are important considerations,
so deciding the number of refugia will be a trade-off between detection
and practicality. Refuge material was evidently an important consideration
in determining how many refugia surveyors would be prepared to carry
and lay. Two surveyors stoically said they would lay as many as required(!),
whilst the others averaged 28 for tin, 60 for felt (ranges 8-50, 15-100
respectively). The workshop participants pointed out that the 'average'
surveyor is unlikely to be as keen as the pilot participants, and
suggested it would be reasonable to expect most surveyors to transport,
lay and check about 20-30 refugia (assuming metal tins). |
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The
workshops discussed the relative merits of corrugated iron sheets
('tins'), corrugated roofing sheets (trade name: Onduline), and roofing
felt as refugia materials. The general feeling was that all have their
own merits, but metal is most effective. Onduline is as good (or better)
in some circumstances, but takes longer to warm up and is probably
inferior overall. However, obtaining metal sheets and cutting to size
is not easy or cheap; and may cause transport, permission and livestock
problems. Roofing felt is the cheapest and simplest option. An 8x1m
roll costs about £8-12 from DIY stores/suppliers and provides about
10-20 refugia (depending on size), i.e. about £0.50-1.00 per refuge.
It can be carried easily and cut en route with a Stanley knife. However,
roofing felt is also the least effective material for attracting reptiles
(other than slow-worms), although by no means ineffective. Snakes
and lizards do use roofing felt, but less so than Onduline and metal.
A sheet of Onduline costs about £9-12 from DIY stores/suppliers and
provides eight 50x50cm refugia, i.e. about £1.12-1.50 per refuge.
We hope to be able to fund or subsidise refugia materials throughout
NARRS; so price should not be a deterrent at this stage. |
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