Reptile ecology, conservation and surveying - Ecology Training UK
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Reptile ecology, conservation and surveying
Recognition
The UK has seven species of reptile, comprising of three lizard species: common
lizard (Lacerta vivipara); sand lizard (Lacerta agilis); and slow worm (Anguis fragilis),
and three snake species: adder (Vipera berus), smooth snake (Coronella austriaca)
and grass snake (Natrix helvetica).
Common lizard – (also known as viviparous lizard) less than 140mm in length with
variable colouration, generally green or brown. Typically it has fine light and dark
spots, lines or flecks creating a striped appearance. Females are less patterned than
males and can be more striped in appearance. The head has a distinctively pointed
snout. This species has a widespread distribution in heathland and grassland
habitats and is the only reptile found in the whole of the UK and Ireland.
Sand lizard – less than 200mm in length, generally stockier and longer than
common lizards. The most obvious characteristic of this species is the bright green
colour of males during the breeding season. The body is patterned with dark but
pale-centred spots, and the head is fairly rounded. This species is very rare and
localized, restricted to particular sandy heaths and sand dunes.
Slow worm – generally less than 540mm in length, this lizard is legless. It is
cylindrical in shape with very small scales giving a shiny appearance. Young slow
worms and mature females can have dark brown or black sides whilst males remain
mostly creamy coloured. Slow worms are widespread and favour tussocky
grasslands, but are almost entirely absent from Northern and Southern Ireland.
Adder – shorter and stockier at less than 800mm, the adder has a distinctive central
zig-zag pattern down the back. Colour is variable, with females tending to be pale
brown to ginger-red, and males a lighter grey or beige, with a stronger pattern.
Adders are absent from Northern and Southern Ireland, but otherwise widespread
where there is suitable heathland habitat.
Smooth snake – the smallest snake at less than 720mm. Normally this species is
grey to brown with dark brown markings. The head has a dark heart-shaped marking,
and the individual body scales lack a raised central ridge/keel that is present on
adders and grass snakes. This species is very rare, confined to dry lowland heath
and sand dunes, namely in Dorset, Surrey and Hampshire.
Grass snake – often less than 1m but occasionally larger. Typically green, olive-
green to brown or grey but variable, has regular dark markings along the side. The
diagnostic feature is a light yellow to orange-red ‘collar’ behind the head. Grass
snakes are widespread in England and Wales, but absent from parts of northern
England, and most of Scotland and Ireland. Grass snakes are strongly associated
with water.
Until a few years ago, grass snakes were considered a single species, Natrix natrix,
with around 14 subspecies described. In 2017 after substantial genetic research it
was proposed that our native grass snake in Britain (Natrix natrix helvetica) should
have its taxonomic identity changed. It was proposed that it is upgraded to Natrix
helvetica, a separate species, rather than a subspecies. There was some mis-
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the case. The reference to “barred grass snake” refers to the fact that the Western
European grass snake (N. Helvetica) invariably has black bars on the flanks, while
this marking tends to be absent in Eastern snakes.
You can read more on the Amphibian and Reptile Conservation website
(https://www.arc-trust.org/news/grass-snake-reclassification) which also provides a
link to the research paper.
General Ecology
Reptiles are cold-blooded invertebrates and, unlike amphibians, they have dry skins.
As ‘ectotherms’, reptiles must bask in order to obtain their body heat from their
external surroundings. This behaviour is useful to the surveyor – see below. Most
reptiles have distinctive overlapping scales.
Reptiles are active between March and October, and hibernate during winter months
unless temperatures are mild. Mating generally takes place in spring once
temperatures have reached 13-15ºC. The common lizard, adder, smooth snake and
slow worm give birth to live young in the summer or early autumn. In contrast, the
grass snake and sand lizard lay eggs – the more typical reptile behaviour. Eggs are
laid in June and hatch in late summer.
Whilst a variety of habitats are suitable for reptiles, particular types are extremely
important. Lowland dry heathland is the most valuable, being the only habitat which
can harbour all six British reptiles. These localities provide the correct mix of warmth,
cover, food supply and dry hibernation conditions for reptiles to thrive. Many grass
snake, adder, common lizard and slow worm populations can also be found in rough
grassland, whilst sand dunes are important to the smooth snake and sand lizard. The
grass snake is an adept swimmer and is strongly associated with the presence of
aquatic habitats. Hedgerows and woodland edges can also be valuable.
All the British reptiles are carnivores but they take a wide range of prey. Grass
snakes are able to catch small amphibians and fish, but take terrestrial prey such as
voles or mice given the opportunity. Smooth snakes predate lizards, the young of
other snakes and small mammals, whilst adders prey mostly on short-tailed voles
and mice. A major part of the slow worm’s diet is slugs, though they will also feed on
other invertebrates and even the occasional young rodent or baby reptile. The
common and sand lizards feed on invertebrates.
Conservation
Current legislation attempts to ensure that British reptiles have some degree of
protection. Common lizard, slow worm, adder and grass snake are all protected
under Section 9 of the Wildlife and Countryside Act 1981 against injuring, killing or
selling. Only the sand lizard and smooth snake are fully protected under the Wildlife
and Countryside Act, 1981 (Section 9) and Regulation 9 of the Conservation of
Habitats and Species Regulations 2017 against killing, injuring, capture, damaging or
destroying a breeding or resting site, intentionally obstructing access to a place used
for shelter, keeping, transporting or selling. This means that not only are the animals
themselves protected, but so are their habitats.
Development sites in the UK that have the potential to harm these protected reptiles
must show that every reasonable effort has been made to avoid breaking the law.
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www.ecologytraining.co.ukThis includes carrying out adequate surveys and undertaking mitigation, such as the
translocation of the reptiles to other appropriate locations.
Habitat management is an important component of reptile conservation.
Organisations such as the Herpetological Conservation Trust advise on, and
carry out, suitable management practises; for example the creation of fire
breaks and the control of tree cover, bracken and invasive scrub in heathland.
Surveying and Mitigation for Reptiles
- Survey timing and weather
Reptile surveying is highly constrained by the time of year and the weather.
As the table below demonstrates, reptile surveys can only be conducted during the
summer months as reptiles are hibernating during the winter. April, May and
September are the best months to conduct a survey because the air temperature is
fairly cool so the reptiles need to bask in the sun to become active. Basking animals
are easier to find and capture, whereas on hot days in mid summer they are more
active, so do not need to bask as much and are therefore more likely to be foraging
in the undergrowth.
J F M A M J J A S O N D
No
Active surveys from March to June and in
surveys
September/October.
No
Surveys are limited by high temperatures No survey– reptiles
Surveys survey–
during July/August in hibernation
reptiles in
Peak survey months are April, May and
hibernatio
September
n
Capture and translocation programmes can
be conducted only while reptiles are active
Scrub
Mitigation (March to June and September/October). Scrub clearance
clearance
Trapping is limited by high temperatures
during July/August. Scrub clearance
Surveying is also weather dependant, even on a day to day basis. The best
conditions for surveying are at temperatures between 10 ºC and 17º C, with
intermittent and hazy sunshine, and little or no wind. These temperature
requirements also mean that it is generally best to survey at 9am -11am, and 4pm-
7pm during April and May.
- Survey techniques
Artificial refugia
This is the most efficient method of surveying (and capturing) reptiles and is based
on their tendency to hide under debris that is exposed to the sun, thus warming up
whilst avoiding predators. It involves placing a series of artificial refugia around the
site, mapping where they are, leaving them for a week and then returning to check
for reptiles during periods of suitable weather. Tins (corrugated iron) which are no
more than 1m2 can be used, as can other heat absorbent materials such as sheets of
roofing felt (0.5m²), black plastic or wood. Tins are recommended for snakes, and
roofing felt is more suitable for surveying slowworms and other lizards. The artificial
refugia should be placed amongst the vegetation, but must still be exposed to the
sun. Five visits to the site are required in order to determine the size of the
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the end of the survey period.
Observations and hand capture
One method of surveying is to stalk and, if necessary, capture the reptiles by hand.
This requires the surveyor to walk slowly and quietly, looking for potential shelter
sites (e.g. turning over rocks or logs) and basking sites. Particular attention should be
given to south facing slopes, banks and pits because they are warmer and ideal for
basking reptiles as well as log and rock piles. Once a reptile has been located the
number, species and location can be recorded. If capture is thought necessary then
the easiest way to capture it is to pounce on it with a cupped hand, but you must be
careful not to crush it. This method may cause some disturbance to the habitat, so
minimise damage by, for example, returning rocks to their original position.
- Capture and Translocation Programmes
Once a survey has identified that a reptile population is present on a development
site, a capture and translocation programme will be required. A translocation exercise
is the process of moving a population of reptiles from one site to another. Several
points need to be considered when choosing a suitable receptor site:
Is the habitat suitable for reptiles – e.g. south facing slope, suitable places to
hibernate.
If there is not an existing population of reptiles on the new site, why is this? Is the
habitat unsuitable in some way?
If there is a large existing population of reptiles at the receptor site, it may
become over-populated if a new population of reptiles is moved there. This may
have a negative impact on the existing and/or new population of reptiles.
Are there other areas in the vicinity that the reptiles can disperse to?
The reptiles should be captured by hand from underneath the refugia during periods
of suitable weather. Much care and skill is required for this, as reptiles, are easily
damaged and also very fast when warmed up. Training by an experienced ecologist
is required. DO NOT attempt to pick up adders and any work on smooth snake and
sand lizard requires an appropriate European Protected Species Licence.
Reptile fencing can be used to prevent reptiles from re-colonising the development
site. It is usually made from thick polythene, which is about 60cm high and is also
buried into the ground so that reptiles cannot get under the fence (see attached
leaflet).
- Habitat enhancement
To improve the receptor site as a good habitat for reptiles, some habitat management
and enhancements may be required. For example, construction of hibernaculum or
log pile refugia Areas of grassland should not be mown during the summer, but in
order that the habitat does not become too shady, scrub may need to be cleared
during the winter.
References and Further Information
Beebee, T. and Griffiths, R. (2000) Amphibians and Reptiles. Harper Collins
Publisher, London.
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www.ecologytraining.co.uk Field Studies Council (2003) Guide to the Reptiles and Amphibians of Britain and
Ireland. FSC Publications, Shrewsbury.
Gent, T. and Gibsin, S. (eds.) (2003) Herpetofauna Workers’ Manual, JNCC.
Sutherland, W.J. (ed.) (1996) Ecological Census Technique – A handbook.
Cambridge University Press.
https://www.froglife.org/info-advice/amphibians-and-reptiles/ there are various
leaflets about British reptiles, either to view on line or to order a copy.
http://www.herpetosurveys.co.uk/surveymethod.htm
http://www.arc-trust.org/
https://www.gov.uk/guidance/reptiles-protection-surveys-and-licences
https://www.cieem.net/data/files/Resource_Library/Technical_Guidance_Series/C
SS/CSS_-_REPTILES_April_2013.pdf - CIEEM competencies for reptile species
survey
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