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NAAMP III Archive - surveys
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Patuxent
Wildlife Research Center
NAAMP III Archive
- surveys
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by Alphabetical Order | Archive by Category
Steve Gibson
Joint Nature Conservation Committee
Monkstone House, City Road
Peterborough, UK
Tel: 44 1733 866815
e-mail: gibson_s@jncc.gov.uk
Introduction
The native British amphibian fauna is sparse, consisting of one frog (Rana
temporaria), two toads (Bufo bufo and B. calamita) and
three newts (Triturus cristatus, T. vulgaris and T. helveticus).
The paper describes work to date on developing a national amphibian monitoring system, parallel developments for monitoring terrestrial mammals from which lessons can be learnt, and an outline of a possible monitoring system. The development is being carried out by the Joint Nature Conservation Committee (JNCC), the body through which the statutory conservation agencies for Scotland, England and Wales deliver common responsibilities.
The monitoring is restricted to the three native newts and the two native widespread anurans (B. bufo and R. temporaria). All these species can only practically be monitored in the aquatic phase, with the possible exception of B. bufo which could be counted during its breeding migrations.
I hope that this paper will stimulate some of you to get in touch if you have solved, or are having to face, similar problems to those I currently face in developing monitoring of non-calling aquatic species. There is doubtless much shared experience we can mutually exploit. I am particularly keen to hear from anyone who has been able to identify species/habitat associations for these, or similar, species, and anyone who has developed, or is similarly trying to develop, a system based around presence/absence in sampling units, and the issues relating to determining presence or absence.
The British herpetofauna
All native species except B. calamita are widespread in their distribution:
R.t. is found in c.98% of Britain's 10km squares; B.b. in
c.70%; T.c. & T.v. in c.40%; T.h. in c.30%.
Work to date
Standardising field techniques
In 1993/4, the JNCC commissioned work aimed at standardising field techniques.
This was initially a questionnaire and literature survey to review current techniques,
of which there were many (Griffiths & Raper 1994). Three main techniques
for newts (head counting by torch light, bottle-trapping and netting, with egg-searching
also for T. cristatus) and a system for estimating breeding female
frog numbers from spawn mat area were then trialled on a large number of populations
(Griffiths, Raper & Brady 1996).
The main findings are described.
Common frogs
Newts
- there is considerable variability between ponds and between nights in results obtained from any of the methods and therefore no relationship between sample results and actual population could be derived
- however, it was possible to specify ranges of counts, using SD, 95% and 99% confidence limits to allocate sites to average, above average, good and excellent categories
- in order to detect presence/absence, if all three field methods were used at any site, there was a 1.2% chance of failing to detect great crested newts and a 2% chance of failing to detect the other newts even if they were present.
Failure rates (%) for the different methods deployed individually were: (data)
Thus, frog breeding numbers can be estimated, but only presence/absence, with known certainty, is possible for newts.
Fluctuations in populations
A piece of work carried out independently is concerned with fluctuations in
a Triturus cristatuspopulation over the last decade (Cooke 1994 &
1995). The highest annual count was found to be 60 times the lowest annual count,
confirming the results described above. Furthermore, almost complete breeding
failure for three years had no detectable long-term effect on the number of
adults counted at night, giving some indication of the magnitude of change any
monitoring programme would need to be concerned with.
Parallel work on mammal monitoring
The JNCC and its sponsoring Government Department, the Department of the Environment,
are jointly funding a one-year study to scope a monitoring programme for British
terrestrial mammals. Out of this will come a large amount of information relevant
to amphibian monitoring including:
- a consideration of sampling frame issues;
- a review of habitat/vegetation/landscape surveys of relevance;
- the development of paradigmatic associative and process-based models which help to optimise sampling strategies, and can be used to develop species distribution predictions to inform the planning process;
- and development of the Population Viability Analysis approach to a point
where it is able to identify biologically significant and insignificant changes
in population status.
A possible monitoring programme
There are a number of constraints on the development of an amphibian monitoring programme in Britain, not least of which is the relatively small time-window within which all survey work must be completed. For the anurans this can be as little as 3 weeks, with the exact start determined by the geographic location, and for the newts a few months. This suggests that a well-managed and motivated volunteer force could be preferable to a professional field team for the collection of data.
The design of an appropriate sampling frame will be crucial to the success of the monitoring. Britain currently undertakes a national assessment of the countryside each decade based upon a stratified (by Land Class - an integrated assessment of landscape, soil and ecological features -) sample of 1km squares. The 1 km square may be a similarly appropriate sampling frame for amphibian monitoring, with the advantage that similar scale data can be more easily compared than multi-scale.
It is envisaged that the monitoring programme will be based upon presence/absence assessments, either for each sampling unit, or for each water body within each sampling unit (a current study is looking at defining and categorising water bodies), with known errors derived from the work described above. These data will probably be used with habitat/vegetation/landscape data to build predictive distribution models for informing the planning process and conservation policy, as well as for indicating the status of the population in national and regional terms.
Population viability analysis could be used to identify limits of acceptable
change, although it will probably be necessary to investigate aspects of the
ecology of the species in the longer term to improve the data, and long-term
surveys at a few populations, probably run by local voluntary groups, may be
an efficient way of doing this, collating and analysing the data centrally.
References
Cooke, A.S. 1994. Fluctuations in night counts of crested newts at eight breeding sites in Huntingdonshire 1986-1993. In: Gent,T., & Bray,R. (eds.). Conservation and management of great crested newts: Proceedings of a symposium held on 11 January 1994 at Kew Gardens, Richmond, Surrey. English Nature Science Report no. 20. English Nature, Peterborough, UK.
Cooke, A.S. 1995. A comparison of survey methods for crested newts (Triturus cristatus) and night counts at a secure site, 1983-1993. Herpetological Journal, 5: 221-228.
Griffiths, R.A. & Raper, S.J. 1994. A review of current techniques for sampling amphibian communities. JNCC Report No.210. Joint Nature Conservation Committee, Peterborough, UK.
Griffiths, R.A., Raper, S.J. & Brady, L.D. 1996. Evaluation of a standard method for surveying common frogs (Rana temporaria) and newts (Triturus cristatus, T. helveticus and T. vulgaris). JNCC Report No.259. Joint Nature Conservation Committee, Peterborough, UK.
U.S. Department of the Interior
U.S. Geological Survey
Patuxent Wildlife Research Center
Laurel, MD, USA 20708-4038
http://www.pwrc.usgs.gov/naamp3/naamp3.html
Contact: Sam Droege, email: Sam_Droege@usgs.gov
Last Modified: June 2002