But I thought ecological consultants were arguing that solar farms benefit wildlife (and newts especially)? Heaven forbid a large population of newts should be found close to the the boundary of a proposed solar farm in Kent. Oh wait...
According to Mr Hutchinson, a “lack of sufficient survey effort” by the developer in respect of great crested newts meant he refused to support the plans until a proper survey of newt numbers was carried out to his satisfaction.
There are advantages and disadvantages to translocating reptiles to sites that are located nearby and sites that are more distantly located.
In attempting to recommend appropriate translocation distances I will take a closer look at the previously identified negative factors that may influence the location of a proposed receptor site. Since this is likely to be rather a long blog post I will split the article into two sections. This is Part 1. Part 2 will follow in due course.
Availability of Receptor Sites
The more land area that is available for review, the greater the choice of suitable receptor sites that are likely to be found. If distance restrictions are too severe the availability of high quality receptor sites may be compromised.
Some reptile species have well defined home ranges. Detailed studies on the home range size of lizards are rather limited, but available information suggests that most are relatively small and can probably be defined by low hundreds of square meters (Beebee and Griffiths, 2000). Dispersing individuals (especially juveniles) may move over greater distances. Species that may appear to be rather sedentary (e.g. slow-worm) may actually display seasonally influenced movement patterns (e.g. Riddell, 2000), although the extent of such movements are likely to be site specific. Viviparous lizards can attempt to vacate adjacent receptor areas and return to their place of capture, even climbing over so-called reptile exclusion fencing in the process (pers. obs). Similar behaviour has been observed in grass snakes (pers. obs.) and adder (Whiting and Booth, 2012).
British snakes have larger home ranges than lizards. Some published studies have suggested that grass snakes can move over large areas with home ranges calculated as several hectares (e.g. Madsen, 1983). Like slow-worms, movement of grass snakes can be influenced by season (e.g. Reading and Jofre, 2009). Female grass snakes lay eggs and may display extensive movements before and after oviposition (Madsen, 1983). Adder also display seasonal movements, with snakes moving between winter hibernacula and summer foraging sites (e.g. Presett, 1971; Andersson, 2003). Such movements may occur across a kilometre or more, even through apparently unsuitable habitat (e.g. through mature woodland).
Human-wildlife conflicts following development may be an important consideration if species such as adder are translocated into nearby areas. In these situations, consideration must be given to ensuring that such conflicts are minimised (e.g. through installation of permanent exclusion fences and appropriate habitat management work). In some cases it may be necessary to translocate adder to sites that are located sufficiently far away to prevent homing so as to minimise potential risks to both people and snakes. Such situations may arise during the construction of housing developments, schools, hospitals etc. Although the actual risk of a person being bitten by a translocated adder is probably very low, the perceived risk may be considered much higher by the public. When stories about snakes and children hit the press, significant negative publicity that undermines conservation actions can result. These issues need to be carefully considered.
Increased dispersal has been found to be a significant factor affecting the welfare of translocated animals (Harrington et. al. 2013). If animals disperse away from a remote receptor site to such an extent that they experience increased mortality or are unable to form a viable breeding population, the translocation should be considered a failure - even if the work meets statutory requirements in preventing animals being killed during development. Problems associated with dispersal and homing behaviour can be minimised through the installation of fencing that restricts animals to previously prepared habitat areas (e.g. Whiting and Booth, 2012). Translocation of reptiles (especially snakes) to more distant receptor sites should be accompanied by increased monitoring effort and this will be discussed in a future blog post.
Loss of Local Biodiversity Interest
The loss of 'local' biodiversity interest may mean different things to different people. A site manager may consider the movement of animals out of her reserve to be a local loss. If the animals are moved into a different local authority area, the planning officer may consider it to be a local loss. Recorders may be concerned about animals being moved between recording areas etc.
The key thing here is to define what we mean by local.
1. relating or restricted to a particular area or one’s neighbourhood...
2. (in technical use) relating to a particular region or part, or to each of any number of these...
In effect then, local has no fixed spatial definition and can mean almost anything provided it is described in the context of neighbourhood or region.
At the risk of sticking my head above the parapet, I will propose a definition that is appropriate in conservation terms for UK reptiles:
Local relates to a predefined area of land that is situated within a specified landscape areawithin a recognised vice county.
i.e. A receptor site is local to a development site because they are both situated in the same character area and the same vice county.
Definitions for character area are dependent upon country. In England, national character areas have been developed by Natural England and appear to replace the previous natural areas, but as far as I can tell use the same boundaries and definitions. Countryside Council for Wales has published a Landscape Character Map (pdf download) and Scottish National Heritage has produced a Landscape Character Assessment. In Northern Ireland, Environment and Heritage Service has published Landscape Character Areas (pdf download).
Vice counties have fixed boundaries that are not influenced by changing political boundaries.
Note that my proposed definition is not limited by distance. Providing the criteria are met, a local site could actually be situated several kilometres away. This may not necessarily be a good thing and other factors are likely to come into play.
Inappropriate Mixing of Genes
I have already discussed the issue of subspecies and race, at least in the context of sand lizard. However, defining the maximum distance that translocations of more widespread species is problematic. Not only are the animals by definition more widely distributed but available research is very limited.
Following publication of a Natural England report highlighting the national decline of adder (Baker et. al. 2004), several projects have been announced that attempt to review the conservation impacts of restricted gene flow. One such project has been organised by Zoological Society of London (ZSL) another by University of Sunderland. However, rather than discouraging translocations these projects may actually collect data that supports the earlier work of Madsen (1999), who found that an inbred population could be restored (at least temporarily) by introduction of a single male adder. Moving animals may actually benefit isolated populations by introducing new genes and therefore increasing reproductive fitness.
After reviewing distribution data for adder in Kent, I believe that genetically distinct populations may be found in different areas (i.e. North Downs and High Weald). Whilst no research is currently planned that will investigate such claims, the movement of animals between different landscape areas could jeopardise future research projects. If the movement of animals follows the previous definition of local, such problems can be minimised. Limiting translocations to local receptor sites should not increase the risk of inbreeding depression.
Differences in Habitat/Geology
Some species have very specific habitat requirements. These may be quite obvious for rare reptiles such as sand lizard, but widespread species can display their own preferences. At least one study in North America has shown that a reptile's prior experience can be an important factor in determining translocation success (Roe et. al., 2010). Slow-worm are sub-fossorial lizards that are frequently encountered in proposed development sites. Animals that have become accustomed to sites with disturbed ground (e.g. old allotments) may have difficulty in establishing populations in receptor sites characterised by different ground conditions (e.g. chalk grassland). The greater the distance that animals are translocated, the more likely it is that receptor sites will be characterised by a different geology. Chalk woodland and clay woodland habitats are very different. Adder favours one, but Kent populations are almost completely absent from the other.
Problems associated with habitat and geology can be minimised if receptor sites are kept local.
Displacement of Individuals from Home Range
Work with some snake species has shown that translocated animals display greater individual movements than undisturbed individuals (e.g. Roe et. al., 2010). These increased movements can result in higher mortality (e.g. through increased predation, movement into unsuitable habitat or roadkill). A large-scale translocation project described by Kyek et.al. (2007) ensured that animals were able to move from receptor areas through suitable habitat corridors back to enhanced habitat areas around the completed development. Although individual movement during this project may still have been high, released reptiles were less likely to disperse into unsuitable habitat.
Whilst the number of UK projects that publish post translocation monitoring results are limited, available reports tend to suggest relatively low numbers of observations of released animals. Whilst some of these results may be due to sample effort (e.g. Lyle, 2008) other reports have suggested low detectability in a high quality but complex habitat (e.g. Cresswell et. al., 2012). It is possible that low encounter rates of post translocation snakes are caused by dispersal of animals away from release areas. At sites where the species has not previously been recorded, such dispersal could result in failure of the translocation project due to animals dispersing away from each other across a large area. In these situations the apparent health of individual animals may remain high, but breeding success becomes less successful over time. Whether observed patterns of apparent population expansion are simply due to individual dispersal away from release areas or a genuine increase in population size remains unclear.
On one hand translocating reptiles to sites within or close to their existing home range may increase homing behaviour that results in conflicts with the residents of new developments (and their pets!). On the other, releasing animals at receptor sites located outside of their home range may increase the risk of translocation failure. It is important to consider that a local site may still be located beyond the home range of a translocated animals.
I warned you it was going to be a long post!
Part 2 will address issues relating to stress, disease and potential impacts on other species.
Andeersson, S. (2003) Hibernation, habitat and seasonal activity in the adder, Vipera berus, north of the Arctic Circle in Sweden. Amphibia-Reptilia, 24, 449-457.
Baker, J., Suckling, J. and Carey, R. (2004) Status of the adder Vipera berus and slow-worm Anguis fragilis in England. Natural England.
Harrington, L. A., Möhrenschlager, A., Gelling, M., Atkinsone, R. P., Hughes, J. and Macdonald, D.W. (2013) Conflicting and complementary ethics of animal welfare considerations in reintroductions. Conservation Biology, 27, 486-500.
Madsen, T. (1983) Movements, Home Range Size and Habitat Use of Radio-Tracked Grass Snakes (Natrix natrix) in Southern Sweden. Copeia, 1984, 3, 707-713.
Madsen, T. (1999) Restoration of an inbred adder population. Nature, 402, 34-35.
Presett, I. (1971) AN ecological study of the viper Vipera berus in southern Britain. Journal of Zoology, 164, 373-418.
Reading, C. and Jofre, G.M. (2009) Habitat selection and range size if grass snakes Natrix matrix in an agricultural landscape in southern England. Amphibian-Reptilia, 30, 379-388.
Riddell, A. (2000) The special ecology and ranging behaviour of the slow worm Anguis fragilis. MSc thesis, University of Kent.
Roe, J.H., Frank, M.R., Gibson, S.E., Attum, O. and Kingsbury, B.A (2010) No place like home: an experimental comparison of reintroduction strategies using snakes. Journal of Applied Ecology, 47, 1253-1261.
Whiting, C. and Booth, H. J. (2012) Adder Vipera berus hibernacula construction as part of a mitigation scheme, Norfolk England. Conservation Evidence, 9, 9-16.
There seems to be a general consensus that reptiles should be either retained on site or moved into an adjacent area of land. Translocation of reptiles to more distant receptor sites is considered to be a 'last resort' strategy.
Examples of published documents that attempt to provide guidelines for UK reptile translocations have been produced by Herpetofauna Groups of Britain and Ireland (HGBI, 1998), JNCC (Clemons and Langton, 1998), English Nature (Moulten and Corbett, 1999, English Nature, 2004) and Highways Agency (2005).
All organisations emphasise the importance of in situ mitigation within the development site itself. Avoiding impacts is clearly the best outcome for reptiles and can be the cheapest option for developers (particularly when delays caused by capture and relocation work are considered). Of course it isn't always possible for new developments to avoid disturbance. Whilst some form of on site relocation may be possible, things get more difficult when ex situ receptor sites are required. Although Clemons and Langton (1998) make no recommendations over distance, both HGBI (1998) and Highways Agency (2005) recommend that receptor sites should be 'close' to the development. Natural England (2004) seem to accept that receptor sites can be:
some distance away
Translocation of slow-worms from a Canterbury development attempted to follow the HGBI (1998) guidelines and involved the movement of animals to a receptor site located within 1 km (Platenberg and Griffiths, 1999). Can 1 km be considered close? HGBI (1998) attempt to define the distances acceptable for translocations:
at least within the same county or similar administrative area, and the same geology and habitat type
In this context 1 km is very close indeed. But clearly the HGBI (1998) definition is rather broad. What is meant by 'county'? Administrative county? Vice county? What about unitary authorities? 'Kent' includes areas that are governed by Kent County Council. However, the Hoo Peninsula is part of Medway Unitary Authority. Is it wrong to translocate reptiles between Kent and Medway? Since Kent is a large county it includes two vice counties; East Kent (VC15) and West Kent (VC16). Is it acceptable to move animals between vice counties? Both Sheerness and Faversham are located within the same local authority area (Swale). However, Sheerness is situated on the Isle of Sheppy. Is is acceptable to move animals between mainland and island sites, even if they are situated within lthe same local authority?
As a recorder I would prefer that reptiles are relocated to areas within the same recording unit. This would help to ensure that the status of populations are maintained in a manner that does not confound future monitoring work. Recording units could be represented by 1 km squares, 10 km squares or vice counties. However, as I will discuss in a future blog post even this obstacle can be overcome (at least to some extent), providing the donor population and receptor site are clearly recorded and results are made publicly accessible.
Of course reptiles do not recognise such artificial boundaries. Although HGBI (1998) imply that it is acceptable to translocate a population several tens of kilometres from one side of a county to another - what about animals occupying development sites that are situated on the boundary? Would it perhaps be better to relocate these animals to a site that is closer, but located in a different county? Restricting the movement of animals to locations within an administrative area may impose unnecessary constraints on a mitigation project that do not contribute to meaningful conservation outcomes.
In a study that investigated the feasibility of introducing grass snakes into the London Wetland Centre, McGrath (2004) acknowledged that introduced animals should originate from a site that is located:
in the same geographic region
McGrath interpreted this as a site located in:
London and otherwise the south-east of England.
That's quite a large area. McGrath subsequently suggested that since only one sub-species of grass snake is native to Britain:
populations from Britain as a whole could be accepted
McGrath seems to be suggesting that the limit on translocation distance should be defined by genetics. However, I wonder if defining genetic variability by sub species is perhaps too simplistic. The movement of sand lizards between Merseyside and Dorset would I suspect be rather frowned upon, even though the animals are the same (sub) species. In their Sand Lizard Conservation Handbook, Moulton and Corbett (1999) consider translocation and advise:
The animals used should be of the right genetic type for the area. The three different regions ie. Merseyside, Weald and north Surrey and Dorset support populations that appear to be different and these may represent distinct “races”. Therefore any re-introductions must avoid mixing (or the possibility of mixing) of these “races” and where possible should use the stock most appropriate for the site.
Perhaps distinct genetic races are less likely to be prevalent in species such as grass snake that are widely distributed across England and Wales. Grass snakes subsequently introduced to London Wetland Centre originated from Holborough in Kent (Anon 2011) - a site located 50 km away. Other long distance translocations have also been publicised in the media. One such project involved the translocation of several thousand reptiles (multiple species, including adder) from Essex to Wiltshire; a distance of over 150 km. In an attempt to promote good practice, Cresswell et al describe mitigation work involving viviparous lizard and adder along the A74 trunk road near the Scottish Border:
Best practice in this regard dictates that, wherever possible, reptiles should be relocated to locations adjacent to or in the immediate vicinity of their existing home ranges or population centres. Only as a ‘last resort’ should they be moved.
Difficulties in identifying suitable adjacent habitat meant that adder:
would need to be translocated to a suitable ‘receptor site’ some distance from the scheme
The distance to this receptor site is not disclosed.
Since translocation projects have been undertaken that involve the movement of reptiles over large distances, is there still a need for guidelines to recommend local receptor sites? In attempting to answer this question I've reviewed available literature to identify relevant issues. These are listed as positive (+) and negative (-) factors:
Short Distance Translocations
+ Species populations are maintained in the local area.
+ Species with large home ranges are less likely to be displaced.
+ Lower captivity and transport times will help to minimise stress and thus reduce post release mortality.
+ Risk of disease transmission between populations minimised.
- Receptor sites may be unavailable.
- Even if available, there is likely to be less choice possibly resulting in selection of sites that are of a lower quality.
- Homing behaviour of some species could result in animals moving back into areas inappropriately.
Long Distance Translocations
+ Greater choice of high quality receptor sites.
+ Translocations can benefit conservation through targeted (re)introductions.
+ Species with homing behaviour less likely to return.
- Loss of local biodiversity interest.
- Increased risk of inappropriate mixing of unique genetic races.
- Movement of animals into areas with different habitat/geology that may increase dispersal and mortality.
- Increased risk of moving species out of their natural range (even if habitat/geology appears the same).
- Movement of individuals out of their home range may increase risk of homing and dispersal, causing increased mortality through predation, road kill etc.
- Increased stress through longer captivity and greater travel distances.
- Increased risk of disease transmission to new areas.
- Possible unforeseen impacts on species already present at receptor site.
Available information suggests that whilst there may some tradeoffs in choosing local receptor sites, translocating animals over long distances introduces many variables that significantly increase the risk of the translocation failing. The next question is how far is too far?
Anon (2011) Reptiles and Development. MKA Ecology.
Clemons, J. and Langton, T (1998) Species translocation. In Herpetofauna Workers Manual, Joint Nature Conservation Committee.
Cresswell, W., Hay, J., Whitworth, R., Head, M. and Penniston, L (2012) Moving lizards and snakes from the path of new roads and improvements: how to get it right. Creswell Associates.
Herpetofauna Groups of Britain and Ireland (1998) Evaluating Local Mitigation/Translocation Programmes: Maintaining Best Practice and Lawful Standards. HGBI Advisory Notes for Amphibian and Reptile Groups.
Highways Agency, (2005) Design Manual for Roads and Bridges Volume 10 Section 4, Part 7, HA 116/05 Nature Conservation Advice in Relation to Reptile and Roads, HMSO, London.
McGrath, A. (2004) Introduction of Grass Snakes to the London Wetland Centre: A Feasibility Study. MSc Thesis. Imperial College London.
Moulton, N. and Corbett, K. (1999) The Sand Lizard Conservation Handbook. English Nature.
Platenber, R.J. and Griffiths, R.A (1999) Translocation of slow-worms (Anguis fragilis) as a mitigation strategy: a case study from south-east England. Biological Conservation, 90, 125 - 132.
Biodiversity offsetting is certainly encouraging journalists to use some rather descriptive terms.
It looks like the current scheme is going back to the drawing board and won't be on public display until much later in the year. Perhaps the concerns of conservation organisations have actually been listened to?
Hopefully there is still time for the powers that be to get revised herpetofauna mitigation guidelines properly drafted.
In 2005 Natural England (then called English Nature) published a document that offers advice to developers on issues related to reptile survey and mitigation work. The document is still available and includes useful information, including a summary of the critical factors that should be taken into account when selecting a receptor site:
"You should take into account a number of factors when selecting sites, including agreement from the landowner and local interest groups, site safeguard, assurance of long-term favourable management, and access for monitoring. Locating a suitable release site can take many weeks of survey effort, fact-finding and liaison. If no suitable site can be found, then it is possible that the development will be prevented from proceeding in its original form. "
By referencing this booklet, together with books, published papers and various reports, it is possible to propose reptile receptor site selection criteria. Some of these factors will be further discussed in future blog posts. I will then use these criteria to propose a simple scoring system that allows different proposed receptor sites to be compared.
Ideally, reptiles should be retained on site or released into an adjacent area of land. When ex situ mitigation exercises are being considered, the location of a proposed receptor site is often influenced by many different factors that may result in animals being moved over much greater distances and this will be discussed in a future blog post.
The proposed receptor site should comprise an area that is at least as large as the area of reptile habitat that will be lost to development. If the proposed receptor site is smaller, available (including enhanced) habitat must be of a sufficiently high quality to support the animals being translocated. Ideally, receptor sites should be both larger and include proposals to enhance existing habitat.
3. Existing Habitat
Receptor sites must include habitat that is suitable for foraging, sheltering and protection. Proposed receptor sites that consist of unsuitable habitat are likely to require significant enhancement work before reptile translocation is possible. Habitat enhancement work on such sites can involve considerable effort and it may take several years before the vegetation sward is sufficiently well established to support translocated reptiles. Determining the suitability of habitat for reptiles includes consideration of many different factors and these will be explored in a future blog post.
4. Extant Reptile Population
The proposed receptor site should not support a population of the species to be relocated, but must be capable of supporting such species with appropriate habitat enhancement works. Additional survey work may be required at the proposed receptor site to determine likely presence of species. This is important to ensure that the mitigation works do not result in a net loss of reptile populations. Although it may be possible to translocate small numbers of animals into an existing population, it is important to ensure that a site's carrying capacity is not exceeded. It is also possible that concerns over disease transmission may make such additions to existing populations undesirable.
Reptiles are preyed upon by a wide range of different predators. In some situations the local abundance of a predator could reduce the likelihood of translocated animals establishing a successful population. Species that may be particularly problematic will be discussed in a future blog article.
6. Site Safeguards
The proposed receptor site should not be subject to planning or other threats (including unsympathetic management work) for the foreseeable future).
7. Site Management
The proposed receptor site should be subject to a written, agreed and funded management agreement. The management agreement should include reference to any additional works that are considered necessary to help establish translocated animals.
8. Site Monitoring
The proposed receptor site should be subject to a written, agreed and funded monitoring programme. The time required for monitoring and the extent of monitoring works required are likely to be determined by the size of the reptile population and impacts of disturbance. Proposed objectives will be discussed in a future post.
[update 1/8/2013] Added predators as an additional selection criteria to consider (ref. Gemma Harding 2004. British Reptile Translocations Guidelines for the selection of receptor sites). Some other factors that folks have suggestedcan be included within criteria 4 - Existing Habitat(e.g. topography, vegetation, temperature, connectivity etc).
Looks like the Wiltshire Wildlife Trust are hell bent on sticking solar farms on (or in this case adjacent) to their nature reserves.
The trust's fundraising officer is quoted as saying:
"The site is not part of the main reserve so it's suitable for purpose," said Steve Webb the Trust's fundraising officer.
"It was an airfield during the war so there's concrete underfoot and it's semi-industrial."
Are the trust suggesting that 'brownfield' sites (i.e. semi-industrial) are unsuitable for wildlife? The implication being that a semi-industrial site is of low ecological value and the installation of a solar farm will not impact upon any biodiversity interest. The trust are this time keen to point out that the land is not part of Blakehill Reserve (where several thousands of those Essex reptiles were also released). Indeed the trust's webpage states:
The independent phase 1 habitat survey of the proposed site did not identify any ecological issues of concern.
However, what is not disclosed in the BBC News article or the rather misleading WWT website is the fact that the site is a designated local wildlife site and offers habitat that could support reptiles (pdf link). Great crested newts are known to occur in the local area and at least one pond is located within 60 m of the site boundary. Despite recommendations made by their ecological consultants in the previously linked report, the trust have this time applied for a licence to undertake gcn mitigation works (pdf download).
surveys did identify a small population of great crested newts (two to be precise) in one of the
neighbouring ponds. These are a protected species so we have applied for a licence from Natural England to safely remove any from the site during construction. After construction we will build a
new pond to provide improved amphibian habitat on the site as well.
Two? What does that mean? A population of two, or only two were observed during survey work. Why aren't the amphibian survey results also available as a download from the trust's website. If there are no ecological issues of concern, why has the site been designated as a local wildlife site and why apply for a great crested newt eps licence?
If an eps licence has been applied for, then clearly there are ecological issues of concern and presumably Natural England will only be able to issue a licence once the trust secure their funds to actually build the solar park? Perhaps this financial venture is a little more risky to prospective punters than it may first appear?
As principal ecologist for Calumma Ecological Services, I am able to put my interest in reptiles and amphibians to good effect. Like most folks that work with wildlife, my activities extend beyond just 'the job' and I am also involved with several local conservation groups. Being the county recorder for reptiles and amphibians in Kent certainly helps me to fill in those spare moments when I'm not busy with the kids!
Calumma Ecological Services is a Kent based ecological consultancy that specialises in protected species surveys and habitat assessments.
Kent Reptile and Amphibian Group
For more information about Kent's reptiles and amphibians visit the Kent Reptile and Amphibian Group's website.
Submit a Record Have you seen a frog in your garden pond? Better yet an adder while out walking?! If you would like to let KRAG know about an amphibian or reptile observation, please complete the online recording card.
Recording Diary KRAG organises a full programme of events throughout the year. For more details about forthcoming attractions, visit the KRAG web site.
Old Blog Posts Still Available Archived posts in the old blog are still available - and will be for ever if I don't work out how to import them into this new site!
Amphibian and Reptile Group of South Lancashire
For more information about the reptiles and amphibians found in Lancashire, visit the ARGSL website.