By Nina Cornish
The common wall lizard Podarcis muralis is one of four species of reptile in Jersey with green lizard Lacerta bilineata, slow worm Anguis fragilis and grass snake Natrix helvetica. The green lizard and wall lizard are found nowhere else in the British Isles except for recently introduced populations of green lizards in Guernsey and England and around twenty separate introduced wall lizard colonies in the UK.
Wall lizards in Jersey live mainly in relatively small, fragmented populations around the east and north east coast, with some very small colonies found on the south coast. Their largest population is at Mont Orgueil Castle, St Martin.
Wall lizards are small and agile, with adults an average snout to vent length of 58.5mm but can grow up to 75 mm. They live for approximately 38 months in the wild and mate in April or May. Wall lizards are oviparous (produce young by means of eggs), with most females laying two clutches per year with an average of five eggs, typically in June and July under low growing vegetation exposed to sunshine. Adult males are the first to emerge from hibernation, generally in February, although unseasonably warm spells of weather can tempt them out in any of the winter months. The females tend to emerge later, usually in early March. In these early months the males become aggressive, chasing and fighting for territory and females.
Wall lizards exhibit tail autonomy, a function which allows the tail vertebrae to break by the lizard contracting it muscles in the tail. This is an important anti-predator mechanism in lacertid lizards, with tails being shed more easily in populations where levels of predation are high. In Jersey the wall lizards’ main predators are rats, certain birds like corvids and kestrels and domestic cats. The older an individual, the more likely it will have suffered the loss of its tail during its lifetime.
Wall lizard populations vary greatly in terms of colouring across their range, although males and females are do have different coloured patterns which allows identification in adults possible. Jersey female lizards can usually be identified as having pale back and side streaks, whereas males have more dark spots and blotches. Both sexes have camouflage markings and coloration, on top of beige – olive coloured background, and with a lighter throat and belly, which can vary in colour from cream to bright orange, pink or red in males. Red throats and belly coloration are commonly observed in breeding males in Jersey.Habits
During the day, wall lizards constantly ‘shuttle’ between areas of light and shade, with the amount of time spent basking per day decreasing as the strength and duration of sunlight increases. As a result, in the early morning one can expect to see the most lizards as they emerge to bask, conversely the least at around midday when most are foraging or inactive in the shade. Activity will then peak again in the late afternoon. Body temperature is regulated utilising this ‘shade mosaic’, i.e. the dappled light effect produced by partial vegetation cover. This means that an ideal situation in terms of vegetation cover would be partial cover in some areas, suitable for foraging and protection from predators with an adjacent area on which to bask and display social, sexual and territorial behaviour.
Wall lizards spend much of the day foraging. In Jersey they feed mainly on Hemiptera (true bugs), Isopoda (woodlice), Hymenoptera (bees, ants etc), Arachneae (spiders), Dermaptera (earwigs), Orthoptera (grasshoppers), Lepidoptera larvae (caterpillars) and Annelids (earthworms). The type of prey varies between sites, not as a matter of preference, more of whatever types of invertebrates are prevalent at each location.
The story behind their distribution and origins
Wall lizards on Jersey are near the northern limit of their geographical range. The species has a wide distribution in continental Europe including France, Belgium, the Netherlands, Germany, the Czech Republic, Austria and the Balkan region, with the northernmost limit of distribution being Maastricht in the Netherlands.
As the name suggests, the wall lizard is most often seen on vertical surfaces including cliffs, rock piles and walls and are especially associated with human habitations. The Jersey populations are typical of other northern European localities in that they are mainly restricted specifically to walls of houses, gardens, fortifications and castles and are widely used provided they are south-facing and have refuges like holes, piles of debris and some form of vegetation cover nearby. Outside the foraging home range of around 15-25 m2, sightings of wall lizard rapidly decrease from the exterior of the forts that they inhabit.
The distribution of wall lizards on Jersey has never really been explained. Despite some intensive local research, no-one has been able to prove why they have such a fragmented distribution or why they have not spread over the Island despite there being large areas of suitable habitat on the north and west coasts. Jersey’s wall lizard presence and distribution was first mentioned in Ansted & Latham’s 1865 The Channel Islands. It stated that wall lizards (although first mistaken for sand lizards), were comparatively rare and were limited to certain districts in the Island. By 1907, Sinel (Notes on the Lizards of the Channel Islands) recorded wall lizards from the cliff, rocks and walls off a thin coastal belt from the east to the north-east coast of Jersey (Le Sueur, 1976). Sinel (1908: The Reptilia, Batrachia, and Mammalia of the Channel Islands, their Origin and Modification by Isolation) also mentions a very interesting historic account concerning French prisoners being held in the Napoleonic forts after the Battle of Jersey (1781) when France attempted to invade Jersey. During this period French prisoners were imprisoned in the Napoleonic forts and it was suggested that they kept wall lizards as pets. Whether these were pets they bought with them or lizards they captured while being imprisoned is uncertain. Alternatively, colonisation could have occurred subsequent to Jersey becoming isolation via rafting (lizards hitching rides on natural materials blown out to sea) or the transportation of quarried granite, between France, Chausey and Jersey. It has been documented that lizards in Jersey were part of a wider pet trade, with lizards being sent from Jersey to England as far back as 1761. Sinel stated in 1908 that ‘The Green lizard is becoming very scarce. This is partly due to the dealers, who have set a price upon its head’. Pyecraft (1927: Jade green lizards of Jersey) wrote ‘The wall lizard, in the locality where I found it, swarmed, but wild horses will not drag from me the place of its retreat, lest a demand be created for specimens. The consequent exploitation by dealers could exterminate it in a single summer!’ By 1947, the pet trade in lizards had reached such proportions that the States of Jersey passed the Wildlife Protection (Jersey) Law 1947, which prohibited the buying, selling, exportation or killing of all reptiles and amphibians of Jersey, as a measure to control the roaring trade for these animals as pets destined for England.
In 1976, Frances Le Sueur published the first distribution map of wall lizards (included below) demonstrating their distribution to be substantially the same distribution as recorded by Sinel in 1907. Since 1976, the wall lizard has been recorded in an additional three-kilometre squares.
In 1988, Chris Perkins (1989: The biology and conservation of the green lizard and wall lizard in Jersey) carried out an Island survey of both wall and green lizards and in 1997, Rosie Smith (2000: Census of Jersey wall lizards Podarcis muralis and ecological correlates of distribution at fort sites in Jersey) studied their distribution and ecology. In 2008 the States of Jersey carried out a public survey to determine the distribution of green and wall lizards. Both St Aubin’s Fort and some very small populations in public and private gardens along the south coast were added to their known distribution. Presence in these areas is thought to be through accidental introductions carried out sometime in the 20th Century.
The lizards fragmented distribution could be partially due to Jersey being on the extreme edge of their distribution. Jersey’s wall lizards may only be able to utilise small areas of suitable habitat due to its northern range (Strijbosch et al. 1980) or their patchy and restricted distribution on the north-eastern, eastern and south coast could have been through introduction following the construction of these forts and towers.
To determine Jersey’s wall lizards’ origins and genetic fitness, a study was carried out to investigate the phylogeography and genetic structure of peripheral populations on Jersey (Channel Islands) and the French Chausey archipelago. In 2014, mitochondrial DNA (cytochrome b gene) from 200 individuals was sequenced to infer the phylogeography of the island populations using Bayesian approaches. In addition, 484 individuals from 21 populations at 10 polymorphic microsatellite loci were genotyped to evaluate the genetic structure and diversity of island and mainland (Western France) populations.
The data provided strong evidence that the wall lizard populations on Jersey and Chausey belong to a single origin. Furthermore, the analyses suggest that this mtDNA clade was isolated from mainland Europe for a long period of time and should be considered native. The origin of the wall lizards on Jersey and Chausey Islands appears to result from increasing sea levels 7,000 BP, isolating island populations from each other, creating independent population histories and hence divergence. It remains possible, however, that there has been occasional gene flow between islands. This could explain the presence of lizards on very small islets in the Chausey archipelago which are unlikely to be large enough to sustain populations for thousands of years independently. In addition, the presence of the most common haplotype (genetic ancestor) in mainland France appeared on the island of Chausey. This might provide evidence of occasional geneflow between mainland France and the islands via retention of ancestral genetic variation or a more recent introduction.
Anecdotal evidence also suggested that human mediated dispersal might be the most likely explanation for one of the four current locations in Jersey, the population on St. Aubin Fort. Although our mtDNA data revealed a different haplotype from other Jersey populations, the nucDNA clusters all Jersey populations together. This suggests that the source population was most likely animals from other Jersey populations and that the difference in haplotype represents a founder effect (the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population). Overall, these results confirm the suspected native status of Jersey and Chausey wall lizards. Thus, the lower genetic diversity of island populations compared to the mainland populations is expected given the lack of gene flow. This may have significant implication for the long-term persistence of the species on Jersey and Chausey Islands. However, since our data suggests the species have been present on the islands for thousands of years it might have already been subject to a severe genetic bottleneck. The species might also have undergone a substantial reduction in abundance more recently.
As this study clarified the native status of the wall lizard population on Jersey, it validates its current full protection status sunder the Conservation of Wildlife (Jersey) Law 2000 (as amended). The law prohibits the unlicensed taking, sale, keeping, injury and destruction of places for shelter (e.g. nest, dens or burrows) and disturbance of any resident animals. Given our results, it is important that Jerseys conservation planners recognise the wall lizard’s restricted distribution, vulnerability to future inbreeding depression, susceptibility to disease, predation and the island’s ever-increasing urban development when determining species management strategies. For instance, should the granite walls and ramparts of historic fortresses where lizards are at highest abundance be developed or destroyed, the population’s continued survival could be at risk. The lizard’s long-term conservation status will depend upon increasing habitat connectivity, especially via coastline protection, connecting their north-eastern and eastern coast populations on the island.
How they are doing?
The most current population estimates were made by Perkins (1988) and Smith (1997) at specific Jersey forts and towers. Due to their protection, restricted distribution and vulnerability there is a need to monitor populations. In 2007 the National Amphibian and Reptile Recording Scheme (NARRS) was launched in Jersey by the States of Jersey Department of the Environment (now Natural Environment) as part of its integrated ecological monitoring programme. The scheme was developed by Amphibian and Reptile Conservation (ARC) and has been run in partnership with Natural Environment and Jersey Amphibian and Reptile Group (JARG) over a 12-year period (2007-2018) to assess and detect changes in the conservation status of Jersey’s native amphibians and reptiles.
In 2019 12-years of NARRS data was analysed to determine changes in occupancy and distribution of Jersey’s native amphibians and reptiles. The result of these analyses determined wall lizard are still restricted to coastal localities. The scheme was not able to determine the wall lizard’s detectability due to their restricted distribution and during the 12-year survey period their occupancy on the island decreased. Additional data was sourced from the Jersey Biodiversity Centre which showed occupancy to have remained stable. The restricted distribution combined with uninformative detection and occupancy results indicate NARRS is not well suited to monitoring wall lizards being better for more widespread species. As a result, the agile frog, grass snake and wall lizard, being rarer and / or more restricted in their distributions, require monitoring with separate surveys. Therefore, future monitoring should (i) apply survey methods specific to the species, (ii) focus on determining species occupancy status at known and suspected sites and (iii) aim to better understand the factors driving species occupancy and detection.
In 2019 new monitoring schemes were designed for amphibian and reptiles with robust and practical data collection in mind. Reptilewatch JE was created with the aim to detect changes in the conservation status of Jersey’s reptiles, through changes in occupancy (levels 1 and 2 surveys) and detect site-level population changes (level 3 surveys). Level 2 Wall Lizard Survey was created to specifically consider Jersey’s wall lizards’ restricted distribution.
How can you help?
We are looking to recruit ‘Wild Volunteers’ to join our Reptilewatch JE team and search for wall lizards at known and suspected wall lizard sites. Wall lizard surveyors are required to carry out six surveys, between March and October, spending 30 minutes at each site visually searching (either walking or looking from a fixed vantage point). You will need training at one of our training events, but no previous experience is needed. Please contact wildaboutJersey@gov.je or go to the Jersey Amphibian Reptile Group (JARG) Reptilewatch JE webpage for more information. There are opportunities for everyone to get involved, with three levels of surveys depending on your interest, available time and experience.
Download the report Phylogeography and conservation genetics of the common wall lizard, Podarcis muralis, on islands at its northern range here