|Common name:||sand lizard|
|Taxonomy:||Lacerta agilis (Linnaeus 1766)|
|Other Names:||Mongolian lacerta|
Madfall tywod (Welsh)
The Sand Lizard is the United Kingdom's rarest native lizard; it is totally harmless to man.
In the UK, the Sand lizard is a specialist of heathland and dune habitats, and native populations can be found in the south of England in the counties of Dorset, Hampshire, Surrey, West Sussex and on the Lancashire coast at Sefton.
A long-standing introduced colony is located on the inner-Hebridean island of Coll and recent re-introductions have expanded its range to the Kent and Welsh coasts.
Like all UK reptiles, the Sand lizard is a carnivore, whose diet is mostly restricted to invertebrates, although any small moving creature may be instinctively taken, sometimes including their own young.
Sand lizards grow to a length of about 8 inches (20cm), with the tail accounting for about half of this length. They can reach an age of twenty years in the wild, in exceptional circumstances.
An individual Sand lizard can have a home range of between 85-2000m2
The Sand lizard is about 8 inches from nose to tail, with a robust build. The length of the tail makes up about half of the total length.
Sand lizards have two pale lines running along the dorso-lateral surface of the body. Between these stripes there is usually a camouflage pattern of black/dark brown and a lighter tan colour. Ocelli (white spots or short stripes running along the dorsal surface) are common, and usually run in a broken line down the very centre of the back, but it is not uncommon to have groups of upto 3 white spots running across the back, between the dorso-lateral stripes.
There is almost never a broken dark line running down the centre of the back, as often found with common lizards.
Throughout the mating season (mid-April to mid-May), the male develops brilliant green flanks. The combination of this green, with the mottled brown back is unmistakable. If you see a greenish lizard that is uniform in body colour, then you have probably seen a Common lizard.
Even out of the mating season, the male retains some green, although much diminished. The flank mottling of the male is finer with more black colouration than the female. Males sport a much larger head and deeper throat than the female of the species.
Sand lizards do exhibit some variety in colour and markings. Melanistic (black) and albino forms occur, but are exceptionally rare.
Sand lizards naturally form three metapopulations in Britain, often referred to as the three 'races':
- The Wealdon race, occupying Surrey, East Hampshire and West Sussex heathlands, and the Kentish coast.
- The Dorset race, occupying the Dorset, Devon and New Forest heaths,
- The Sefton race, which lives on the coastal dunes of West Lancashire, Wales and the Wirral.
Wealdon and Dorset animals are very similar in appearance, and the numerous re-introductions of Dorset animals into Surrey makes it effectively impossible to determine any difference between the two.
The Sefton race demonstrates some clear differences from their Southern kindred. Sefton animals often appear smaller and slimmer (particularly those occupying frontal dunes). Sefton males sport a lighter, lime-green coat when in mating moult, compared to the deeper bottle-green of Southern animals. Both male and female Sefton race lizards have wider and more prominent dorso-lateral stripes, although occasionally, Southern animals demonstrate this wide banding. The wide lines of the Sefton animals provide superb camouflage in their marram grass habitat.
In spring, the difference between the genders is clear. Males develop striking green flanks, and can be readily seen on mounds, defending their territory. Pairs of animals can often be seen basking together.
Out of the breeding season, the differences are more subtle. Males have a stockier appearance, with heavy-set jaws and larger heads. The markings along the flanks of the male are more crowded, with a series of black crazing, compared to the more brown female, which has regular, larger ocelli along her flanks.
Another useful tip, which relies upon the head of the male being larger, is that the eye of the female Sand lizard is usually situated about half way along the head. The eye of the male is situated about a third of the length of the head, closer to the neck.
Could be mistaken for
The sand lizard can be confused with our only other native legged lizard, the common lizard. In particular, green morphs of common lizard are easily mistaken. In the south of England, two additional introduced species can also cause confusion, these are the common wall lizard and the western green lizard.
It is distributed across most of Europe and eastwards to Mongolia, with the following exceptions: the Iberian peninsula, west and south-east France, most of Britain, Italy where it is present only in isolated colonies, European Turkey, most of Greece.
The sand lizard is native, with permanent occupancy within the counties of Dorset, Hampshire, Surrey and West Lancashire since the end of the last Ice Age. Introductions have re-established populations in West Sussex, Kent, Devon, Cornwall and Wales.
In 1971, 35 adult and 5 juvenile sand lizards were introduced to the inner-Hebridean island of Coll. Although this area is outside of the sand lizard's normal range, the Gulf stream provides suitable meteorological conditions, and the colony still exists.
In Surrey, the sand lizard's stronghold is the heathland of the Western part of the county.
Although the Sand Lizard is often thought of as a dry heathland specialist, it has demonstrated a high degree of adaptivity. The colony along the Sefton coast in Lancashire is based upon fixed and frontal sand dune systems, where it successfully survives alongside another rare herpeton, the Natterjack Toad.
Colonies across Surrey and West Sussex are restricted solely to dry heathland habitats that are situated on a sandy or gravel substrate.
The Dorset colonies demonstrate a more catholic taste for habitat type, with dry heath, cliff-top, meadow and even refuse tips being used.
Surrey populations of Sand lizard are strongly associated with definite foci within large areas of dry heath. These foci comprise mature heather, but most importantly have a deep moss structure (up to 12 inches/30cm) underpinning the heather.
The majority of foci are associated with a slope, undulating ground or a small plateau. There must be a mosaic structure of undergrowth and exposed sand, for egg laying.
Sand lizards are diurnal. Once the warmth of the day is detected, Sand lizards will emerge from their burrow. The time of emergence depends upon sunlight and temperature, but in Surrey they rarely emerge in large numbers until 09:30 on warm summer days. The lizard's first requirement is usually to bask, to gain the energy they require to hunt for food.
Sand lizards hibernate throughout the winter months, with males being the first to emerge, usually in mid March.
The Sand lizard diet comprises almost entirely of invertebrates. In particular they appear to enjoy spiders, grasshoppers and crickets.
Male Sand lizards have been known to eat their own young, and the young of Common lizards. This is due an instinctive reaction to fast-moving prey items of an appropriate size.
The lizards eat daily when food is available, but, as with all reptiles, can last for considerable periods without eating.
The Sand lizard uses a combination of foraging and ambush whilst hunting for prey. The lizard will move several metres, pause, scenting the air by tongue-flicking (presumably to aid the detection of prey) and repeat the process.
Upon detection of a possible prey item, the lizard will sprint to the point where movement was detected, pause slightly whilst cocking its head backwards, then strike, grabbing the unfortunate invertebrate.
Should the prey escape, the Sand lizard will chase it, totally focussed upon its prey for up to a couple of feet (60cm). If the prey evades capture beyond this distance, the lizard will ignore it and continue foraging.
The main natural predators of the Sand lizard are Pheasants (although not strictly native to the UK), birds of prey (particularly Kestrels) and the rare Smooth snake.
Mammalian threats come in the form of Foxes, Badgers and Mustalids (Weasels). Corvids (the Crow family) will also attempt to take Sand lizards, but the lizard is usually sufficiently agile to evade these predators. Even woodpeckers have been known to take small lizards. Where Sand lizard habitat borders human habitation, a major predator is the domestic cat.
It is ironic that Britain's rarest reptile, the Smooth snake, predates Britain's second rarest reptile, the Sand lizard. As both of these reptile species share a preference for similar heathland habitat, encouters must occur frequently.
The predator avoidance strategy of the Sand lizard has three phases:
- Initially the animal will remain motionless, relying upon its camouflage for concealment.
- If concealment fails, the animal will flee into deep undergrowth.
- Should the Sand lizard be caught, it may choose caudal autotomy as a last line of defence (the voluntary casting off of its tail). The detached tail will wriggle for several minutes, hopefully distracting the predator, while the lizard escapes. The tail will grow back, but often not to its full length, and a discontinuity in patternation and colour will be evident.
Sand lizards dig burrows for shelter. The same burrow is used for overnight refuge and for hibernation.Burrows have a diameter of around 2 inches (50mm) and a depth of up to 3 feet (1m). The entrance to these burrows is usually hidden in undergrowth, and extends into sandy soil. The burrow will turn sharply after a few inches so that the lizard is out of sight of the entrance, and is often dug into a slope with an upward profile. This may assist with drainage, but is probably due to greater ease of excavation as the burrow remains in the slightly looser surface of the sandy soil.
Occasionally, Sand lizards will dig their own hibernation burrow within the side wall of a rabbit warren.
Towards the end of April, the male Sand lizard, already sporting his resplendent green mating moult, will defend prime territory. Sand lizards can be aggressive, and fights between rival males are not uncommon, although many disputes are settled through competitive posturing.
The females are either drawn to the males or are approached when entering a male's territory. The courtship ritual will begin when a female chooses a suitable mate. Sometimes, the pair circle each-other, with the female frequently lying flat on the ground, turning both hind legs towards the sky and waggling them as a sign of acceptance. After several minutes of this behaviour, the male will seize the female, either at the base of her tail, or mid way along the body.
On other occasions, the male will be more aggressive, and catch the female in his jaws, forcing coitus.
Copulation can last from a few seconds to several minutes, ending with the female departing at high speed into the surrounding undergrowth. The male remains stationary for a few minutes, before resuming the patrolling of his patch, defending it against rival males and mate searching for additional females.
Sometimes, the male will follow the female and bask next to her, mate-guarding her from rival males.
Towards the end of May and in early June, the female digs a series of test-burrows in sand that is exposed to sunlight; presumably checking for egg-laying sites of appropriate warmth and humidity. Between 2 to 16 (usually about 8) eggs are laid in the final burrow, which take between 8 to 10 weeks to hatch. The eggs rely upon the warmth of the sun for development.
Female Sand lizards can be very pre-occupied when digging and are at an increased risk of predation. Recent observations have shown competition for the best egg-laying sites, with dominant females physically removing subordinate females from the best sites, and seizing their egg-burrows.
Some females in the south of the UK have started to produce a second clutch of eggs in the late summer. This is a trend that is likely to to become more marked as global warming raises average temperatures.
Juvenile Sand lizards hatch at the end of August, when they have to fend for themselves with no assistance from either parent; indeed it is not uncommon for adult male Sand lizards to eat juveniles. They can often be seen in twos or threes, apparently hunting together.
Like the adult Sand lizard, the juveniles can be identified by the two light coloured dorso-lateral stripes which extend well onto the tail. The juveniles also have a row of muted ocelli along their flanks.The only animal that a juvenile Sand lizard is likely to be confused with is a juvenile Common lizard. The Common lizard is entirely black when very young, changing to a brassy metallic sheen. Common lizard juveniles do not have the row of ocelli along their flanks.
Juveniles tend to enter hibernation later than adults, at the end of October. Presumably this late hibernation allows time to gain condition to improve their chances for surviving the winter.
Sand lizards reach sexual maturity at between three to seven years of age (in the wild), but can become sexually mature as as early as 9 months of age when captive indoors.
The decline of the Sand lizard is attributed to loss, deterioration and fragmentation of heathland and dune habitat due to development (notably Bournemouth and Liverpool), scrub and tree incursion, uncontrolled fires and a shortage of suitable egg-laying sand on heathland sites (90% loss of prime habitat over the last 100 years).