Action: Translocate great crested newts
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- Four of six studies (including one review and one replicated study) in the UK found that translocated great crested newts maintained or established breeding populations. The review found that populations were present one year after release in 37% of cases and one study found that although translocations maintained a population in the short term, within three years breeding failed in 48% of ponds. One systematic review of 31 great crested newt studies found that there was no conclusive evidence that mitigation that included translocations resulted in self-sustaining populations.
- One review in the UK found that great crested newts reproduced following 56% of translocations, in some cases there was also release of head-started larvae and/or habitat management.
Supporting evidence from individual studies
A before-and-after study in 1990–1993 of six ponds at an opencast coal site near Manchester, UK (Horton & Branscombe 1994) found that translocated great crested newts Triturus cristatus established a breeding population over the first two years. The number of newts captured at the site increased from 473 in 1992 to 892 in 1993 (1,063 released). Between one and 223 metamorphs were caught leaving created ponds and 1–197 leaving existing ponds each year from 1991 to 1993. In 1990–1991, three ponds were created and three others managed for amphibians within a mitigation area for works at the mine. Artificial egg laying substrate (plastic strips) was provided in new ponds. A total of 813 newts in 1991, 250 in 1992 and 625 in 1993 were translocated from mine to conservation ponds. Newts were monitored using drift-fencing with pitfall traps around the ponds and site boundary.
A review of translocation programmes in 1990–1994 for great crested newts Triturus cristatus in England, UK (May 1996), extended in later studies (Oldham & Humphries 2000, Edgar, Griffiths & Foster 2005), found that adults returned to ponds in most cases and bred in 61% of translocations monitored. However, longer-term monitoring over 6–18 years showed that 53% of 15 translocations before 1990 failed. In 1990–1994, adults returned in subsequent years in 92% of 92 cases monitored, although newts were already present at 10 ponds. Seventy-two translocations from development sites involved adults (average: 197; total: 13,115), juveniles (57; 914), larvae (32; 501) and many eggs. Twelve translocations involved collecting eggs and rearing and releasing larvae (average: 643) and juveniles (63) for introduction purposes. Habitat enhancement (e.g. log piles, hibernacula, tree planting) was undertaken in 79% of 28 cases where there was partial habitat destruction. Where there was complete habitat destruction, newts tended to be moved to existing sites. Licenses for all translocation projects between 1990 and 1994 were reviewed and 74 licensees contacted for information. Extra monitoring information was obtained for translocations undertaken before 1990.
A before-and-after study in 1985–1993 in England, UK (Cooke 2001) found that a new breeding population was established from 38 translocated great crested newts Triturus cristatus. Although no newts were observed six years after translocation, ad hoc monitoring over the next few years found increasing numbers of newts. Newts were translocated 100 km from a site in Kent to Cambridgeshire because of habitat destruction during a development project. Adults, metamorphs and larvae were monitored during night spotlight counts in spring and summer each year. No newts were present at the new site prior to translocation.
In an update of previous reviews (May 1996, Oldham & Humphries 2000), a review of 72 great crested newt Triturus cristatus translocation projects carried out to mitigate against development in 1990–2001 in England, UK (Edgar, Griffiths & Foster 2005) found that where follow-up monitoring was conducted, there was evidence of breeding at over half of sites one-year post-development (56%). However, projects did not provide data to compare numbers before and after translocation or to determine whether sustainable populations were established. Only 49% of projects monitored populations, most for two years or less. The average number of newts translocated per project declined significantly from 358 in 1990–1994 to 172 in 1995–2001. Most translocations were to areas within or adjacent to the development site (<500 m). There was a net loss in overall area of aquatic habitat. Licensing information collected by the governmental licensing authorities was analysed and a questionnaire survey sent out to a sample of 153 mitigation projects (47% provided data). Of 737 licensed projects on file, 55% contained no report of the work undertaken, although it is a condition of the licence.
A replicated, before-and-after study in 2005 of nine mitigation projects in England, UK (Lewis, Griffiths & Barrios 2007) found that translocation of great crested newts Triturus cristatus resulted in the maintenance or establishment of populations at all sites. However, after three or more years, numbers captured at five of the nine populations were lower than that prior to translocation or less than the total number translocated. Four populations were classified as ‘small’ (peak count: 1–3) and five as ‘medium’ (16–86). Mitigation projects during development work had been carried out at least three years previously. Between two and 164 newts were translocated at each site between 1987 and 2001. Terrestrial habitat management was also undertaken at two sites and artificial refugia provided at one. Monitoring was undertaken in March–May 2005 using egg searches, torch surveys, bottle trapping and mark-recapture.
A before-and-after study in 2004 of a pond in parkland in Lancashire, UK (Neave & Moffat 2007) found that translocated great crested newts Triturus cristatus established a breeding population. Newts were translocated to the pond from a nearby building site in 2002 and monitored in spring 2004.
A before-and-after study in 2006–2009 in North Lanarkshire, Scotland, UK (McNeill 2010) found that translocations maintained a great crested newt Triturus cristatus breeding population in the short term. Breeding adult counts were higher after translocation (100–299 vs 66–140). Adult survival rate was 43% and there was some recruitment into the breeding population. However, numbers of eggs, larvae and metamorphs suggested breeding failure and low juvenile survival and recruitment. In 2008, no eggs or larvae were recorded in half of the 25 ponds. Metamorph counts decreased significantly from 39 in 2006 to five in 2009. The newt population was translocated from the original site to a created and restored site (29 ha; 600 m away) in 2004–2006. A total of 1,594 newts (1,012 adults) were moved. The original site had been monitored for six years before translocation. Monitoring at the release site was undertaken using torchlight sampling, egg counts and metamorph counts at the perimeter fence.
A systematic review in 2011 of the effectiveness of mitigation actions for great crested newts Triturus cristatus in the UK (Lewis 2012) found that none of the 11 studies captured nor monitoring data from licensed mitigation projects showed conclusive evidence to suggest that mitigation that included translocations resulted in self-sustaining populations or connectivity to populations in the wider countryside. Only 22 of 460 licensed projects provided post-development monitoring data and of those, 16 reported that small, three medium and one large population was sustained. Two reported a loss of the population. The review identified 11 published or unpublished studies together with 309 Natural England and 151 Welsh Assembly Government (licensing authorities) mitigation licence files. Mitigation measures were undertaken to reduce the impact of development and included habitat management such as creating or restoring ponds, as well as actions to reduce deaths including translocations.
In an extension of a previous review (May 1996), a review of 178 great crested newt Triturus cristatus translocation programmes in 1985–1994 in the UK (Oldham & Humphries 2000) found that populations were present one year after release in 37% of all cases (see also Edgar, Griffiths & Foster 2005). In 10% of cases no newts were present the following year. Over half of the projects did not have enough evidence to assess success. Success of monitored projects increased from 59% before 1990 to 78% in 1990–1994. In one project, less than 40% of 1,000 translocated newts remained within a 5 ha managed conservation area. However, those that remained produced 135 (in three ponds) and 567 metamorphs (six ponds) in the first and second year respectively. Male survival over two years was estimated as 46% and translocated newts gained mass (18%). Data from translocation projects was obtained from Natural England licensing records. In the case study, newts were translocated to an adjacent conservation area in 1991–1992. Trees and shrubs had been planted and hibernacula and three ponds created. Newts were monitored using drift-fencing and pitfall traps and using bottle traps.
- Horton P.J. & Branscombe J. (1994) Case study: Lomax Brow: great crested newt project. Proceedings of the Conservation and Management of Great Crested Newts, English Nature, Peterborough, 104-110.
- May R. (1996) The translocation of great crested newts, a protected species. MSc thesis. University of Wales.
- Cooke A.S. (2001) Translocation of small numbers of crested newts (Triturus cristatus) to a relatively large site. Herpetological Bulletin, 75, 25-29
- Edgar P.W., Griffiths R.A. & Foster J.P. (2005) Evaluation of translocation as a tool for mitigating development threats to great crested newts (Triturus cristatus) in England, 1990-2001. Biological Conservation, 122, 1990-2001
- Neave D.W. & Moffat C. (2007) Evidence of amphibian occupation of artificial hibernacula. Herpetological Bulletin, 99, 20-22
- McNeill D.C. (2010) Translocation of a population of great crested newts (Triturus cristatus): a Scottish case study. PhD thesis. Department of Ecology & Evolutionary Biology. University of Glasgow.
- Lewis B. (2012) An evaluation of mitigation actions for great crested newts at development sites. PhD thesis. The Durrell Institute of Conservation and Ecology, University of Kent.
- Oldham R.S. & Humphries R.N. (2000) Evaluating the success of great crested newt (Triturus cristatus) translocation. Herpetological Journal, 10, 183-190