RAUK - Archived Forum - Newt mitigation

New reports on great crested newt mitigation and capture methods

Two important reports on great crested newts have just been published by English Nature. They are available as English Nature Research Reports (free of charge as hard copies from our Enquiry Service û tel 01733 455100, PDFs from our website). The titles, summaries and URLs are reproduced below.

NOTE: If you were invited to participate in the mitigation questionnaire survey in 2002, you will automatically receive a copy of both reports in the post in the next few days (regardless of whether you replied to the questionnaire). If you have changed address since then there might be a problem, so I suggest you ask for copies from our Enquiry Service.

Many thanks to all those who helped with these projects; your information was extremely valuable valuable, and I hope you'll find the resulting research of interest.

English Nature Research Reports Number 575: An evaluation of the effectiveness of great crested newt Triturus cristatus mitigation projects in England, 1990 û 2001. By Paul Edgar and Richard A. Griffiths

http://www.english-nature.org.uk/pubs/publication/PDF/575.pdf

An analysis of great crested newt mitigation projects carried out between 1990 and 2001 was performed by (1) reviewing all licences issued by English Nature and Defra over this period; and (2) a questionnaire survey of a large sample of mitigation projects. A total of 649 licence files covering some 345 mitigation projects were examined from English Nature files. Over half of these contained no report of work undertaken under the licence. A total of 153 questionnaires were distributed, yielding information on 72 mitigation projects.

There has been a steady increase in the number of licences issued for great crested newt mitigation from less than 10 per year in the early 1990s to over 80 per year by 2000. A relatively small number of consultants have carried out most mitigation work on great crested newts. The proportion of in-situ mitigation projects has increased relative to the number of projects involving ex-situ translocation of newts in recent years. The largest numbers of mitigation projects have been conducted in Cheshire and Lancashire. Most projects lasted longer than one year at an average estimated cost of ú15,000-ú20,000 per project. Over this timeframe some 59% of projects spent up to 80 days on mitigation work, and a further 26% of projects up to 240 days. Building developments were the commonest type of development requiring mitigation. Great crested newts were often overlooked in the planning process and were rarely considered as part of wider Environmental Impact Assessments. Most predevelopment surveys that were commissioned were started less than six months prior to the mitigation work commencing. A variety of methods were used in pre-development surveys, but torch counts were used in 80% of projects.

A range of methods was used to catch newts for mitigation, and the average number of newts translocated per project has declined in recent years. This is probably because (1) an increasing number of smaller newt populations are being identified and accounted for within mitigation work; and (2) more projects are focusing on in-situ population management that makes large-scale translocations unnecessary. The number of newts translocated was positively related to the area destroyed by development; the number of capture methods used; capture effort and overall project effort. Less than half of all projects had any post development monitoring. Moreover, it is difficult to determine what proportions of the actual populations were actually captured or whether these became part of a sustainable populations at the receptor sites because of (1) differences in the survey methodologies used before, during and after the developments; (2) the fact that only a single study used a mark-recapture method to establish population size; (3) difficulty in distinguishing between translocated newts and natural colonizers at the receptor sites; and (4) the short-term nature of most follow-up surveys.

Most receptor sites were on the periphery û or immediately adjacent to û the development site and had some degree of connectivity to other areas of potential newt habitat. The number of new ponds created compensated for the number of known great crested newt ponds destroyed, but did not compensate for the total number of ponds lost. Newly created ponds were generally smaller than those lost to development, so the total surface area of water lost to development created was less than the total surface area of great crested newt ponds lost. Of the ponds that were retained as part of mitigation, less than half underwent any management or enhancement. Overall, slightly less than one-third of the great crested newt terrestrial habitat within the development area was destroyed. However, at least 75% of potential great crested newt habitat was affected in over 30% of projects. No post-development monitoring was carried out in 36% of projects.

Where post development monitoring was carried out it continued for up to five seasons, with most projects carrying out monitoring for up to two years. Adult newts were observed to be present at 87% of the sites surveyed one year after the development with evidence of breeding confirmed at 56% of sites. There are insufficient data to judge whether sites subjected to mitigation contained post-development populations that were self-sustaining in the long-term.

However, many respondents to the questionnaire requested more streamlined processing of licence applications, improved guidance for mitigation activities, and better training of personnel charged with providing advice and decisions on mitigation procedures. Although less than 25% of mitigation projects received any wider publicity, when this was the case the mitigation was generally viewed in a positive light by the media. The new guidance introduced in 2001 (ie after the majority of sample projects were implemented) was viewed by most respondents as positive, and should help to remedy some of these issues. Recommendations are made to further refine advice and procedures.

English Nature Research Reports Number 576: An assessment of the efficiency of capture techniques and the value of different habitats for the great crested newt Triturus cristatus. By Warren Cresswell and Rhiannon Whitworth

http://www.english-nature.org.uk/pubs/publication/PDF/576.pdf

This report presents the results of a study undertaken on behalf of English Nature to evaluate the efficiency of capture techniques and the value of different habitats for great crested newts. Licence return data were analysed in an attempt to assess the effectiveness of various different elements of the measures used to mitigate the effects of developments on newts. A further aim of the project was to assess the value of different habitats for newts by investigating the numbers captured in a variety of types of land across England. It was intended that the results of these analyses would help to predict development-related impacts and inform trapping, and other mitigation requirements, and thus help inform the development of best practice in mitigation projects involving this species.

The capture data revealed relatively clear associations between the numbers of newts caught and certain habitats. Four habitats were found regularly to predict the number of newts captured: woodland, arable land, post-industrial habitats and hedgerows. There was also a significant correlation between captures and proximity to breeding ponds, and the combination of habitats and proximity to ponds showed an even stronger relationship with numbers of newts captured. Whilst it is likely that newts were actively selecting the more suitable habitat types such as woodland and hedgerows, the role of arable land as a predictor of newt density and occurrence was more likely to be an artefact of the sampling. However, the results did show that arable farmland with a high density of ponds can support large newt populations. More research on newt habitat associations is required in order to investigate a more useful means of predicting newt density and distribution on the basis of habitat or landuse.

The information provided in the licence records was insufficient to provide clear-cut recommendations as to the type of capture method to use in all cases, because season, habitat, distance from a breeding pond, and life stage of the newts were all complicating factors within the analyses. There was, however, a significant positive correlation between the total number of newts captured and both the number of capture methods used and the overall project scores for capture effort.

Pitfall trapping was the most widely employed technique and generated the largest capture totals (excluding captures of larvae). The effectiveness of pitfall trapping varied considerably depending upon whether or not the trapping operation involved the use of a fence around a breeding pond. Only bottle trapping showed a positive correlation between effort and numbers caught for both adults and larvae.

Far more adults were captured than any other life stage. Netting appeared to be the most effective technique for capturing larvae, and can be useful in capturing adult newts also, but is far more efficient when combined with some form of ædraining-downÆ operation. Although slightly more effective at capturing sub-adults, refuges appeared to be generally ineffective at capturing newts in substantial numbers. By contrast, pitfall trapping was more efficient, particularly in capturing adult newts. As with the use of fences and traps in other situations, the over-riding influence appeared to be the proximity to breeding ponds. By far the most captures were recorded within 50m of ponds and few animals were captured at distances greater than 100m.

Generally the results of the various investigations supported the details and advice presented in English NatureÆs Great Crested Newt Mitigation Guidelines. However, it was also possible to make the following further recommendations:

ò Where the more suitable habitats occur in conjunction with breeding ponds, it is necessary to consider a comprehensive mitigation programme. However, it would be misleading to discount any habitats if closely associated with breeding ponds.

ò The most comprehensive mitigation, in relation to avoiding disturbance, killing or injury is appropriate within 50m of a breeding pond. It will also almost always be necessary to actively capture newts 50-100m away. However, at distances greater than 100m, there should be careful consideration as to whether attempts to capture newts are necessary or the most effective option to avoid incidental mortality. At distances greater than 200-250m, capture operations will hardly ever be appropriate.

ò The use of multiple capture methods has also been shown to be important, particularly (i) if attempting to catch newts away from breeding ponds, and (ii) where, for whatever reason, the early-season elements of an operation to exclude and relocate newts from a breeding pond have been less effective at keeping adult newts out of the pond, and hence some could go on to breed.

ò The significantly better performance of netting as a technique when associated with draining-down operations should be considered when this approach is being proposed. In addition, the increased effectiveness and usefulness of nocturnal searching of terrestrial habitat in the zone beside drift fences, both during the first warmer, wet nights of the early season, for adults; and during similar climatic conditions from mid- August to the end of September for juveniles should also be recognised.

ò It was clear from the data that consistently, sub-adult life stages were captured less effectively than the others. Unless captures over successive seasons are possible, it is necessary to attempt to capture sub-adults in terrestrial habitats away from ponds. However, the analysis of capture results shows clearly that in almost all cases catching newts at a distance from breeding ponds is labour-intensive and inefficient.

ò It has also been possible to identify a clear relationship between æeffortÆ and capture success for bottle traps, meaning that the more traps employed the more newts will be caught. Thus, recommended trap densities could be increased to accelerate captures in key periods (for example, early in the season, to minimise successful breeding in ponds to be cleared).

ò It has also been possible to identify that the efficient capture of juvenile newts relies on rather ænarrowÆ and potentially very important æwindowsÆ in late summer/early autumn. In addition, because of the size and behaviour of juveniles, the details of some mitigation techniques (particularly the quality of installation of drift fences and pitfall traps) are more critical and these methods can be much less successful than for adult newts.

ò The results supported the idea of not attempting to capture newts in terrestrial habitats at temperatures below 5-6oC. The key finding with regard to the influence of weather patterns was that it is seldom worth attempting to capture newts away from ponds during spells of dry weather between June and mid-August inclusive.

ò Very few of the projects provided a clear test of the comprehensive æcompartmentalisationÆ recommended in English NatureÆs Guidelines. Whilst newts were caught in these circumstances, in most cases only small numbers were caught compared to the lengths of fencing and numbers of traps employed. In addition, assessing the amount of excavation etc., necessary to install large amounts of fencing in areas known to contain newts, raised some concerns about the possibilities of incidental mortality when mechanically installing æcompartmentalisingÆ fencing.

ò Where there were no obvious features to ætargetÆ with fencing, capture success along fences declined sharply with distance from ponds, and captures within the 50-100m zone were generally inefficient. Captures on fences (and by other methods) at distances between 100m and 200-250m from breeding ponds tended to be so low as to raise serious doubts about the efficacy of this as an approach, although a small number of projects did report captures on significant linear features at distances of approximately 150-200m from ponds.

ò It is important that mitigation design is based upon a carefully considered risk assessment, with regard to the likelihood of the development-related activities resulting in disturbance, killing or injury of newts and interference with population processes. The scale of the mitigation and the resources allocated to it also needs to take account of the likely outcomes of different mitigation options in relation to these potential impacts, the numbers of newts involved and the likelihood of success of the various mitigation options.

POST ENDS.