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Sand Lizard (Lacerta agilis)

General description

Dorset male sand lizard

Absent from South Wales, the sand lizard is the largest and easily the most striking in appearance of the British lizard species.  Reaching as much as 19cm in length, the sand lizard is altogether a more robust animal than the viviparous lizard and has proportionately shorter legs.  Ground colour of the upper body ranges from shades of pale brown to grey with a vertebral line of ocellated patches or ocelli.  The vertebral line of ocelli is bordered on either side by a lateral line of the same.  Some specimens particularly of the northern race that live in frontal sand dune systems have the overall appearance of lines or stripes and are lighter in colouration when compared to the majority of specimens of the southern race.  The southern race stem from heathland habitat and tend to be slightly darker and more variegated to blend in with the heather.

Gravid Dorset female

The belly is white or cream with small black speckles.   A male sand lizard in full breeding condition is possibly one of the most colourful sights among the British fauna and flora, and displays vivid green flanks and belly.  The tail is proportionately shorter than that of the viviparous lizard.  Melanistic (entirely black) individuals have not been recorded on mainland Britain.

Sexing sand lizards

During the breeding season, the difference between adult males and females is plainly obvious, otherwise the proportionately larger head of the male and slimmer, shorter body length differentiate males from females.

Habitat

Sand lizard habitat requirements centre around sun drenched complex and varied vegetative structure and areas of exposed sandy soil for egg laying.  These exacting requirements are met by two seemingly very different habitats in Britain.

Dorset heathland sand lizard habitat, note areas of exposed sand

The southern populations of sand lizards live on the sandy lowland heaths of Dorset and Surrey.  The northern population of sand lizards live on the frontal sand dune systems of Southport in Lancashire. 

Lizard in typical habitat

Reintroduction programmes involving captive bred animals of stock originally sourced from the northern race have been undertaken at various suitable dune systems in North Wales and are reaching levels of sustainability thanks to the efforts of HCT.

Behaviour

Male sand lizards emerge from their hibernation burrows in late February to mid march and are joined by the females around two weeks later.  The largest males are the last of the males to emerge, and smaller males are often displaced from territories as a result.  Cooler air temperatures at this time of year necessitate basking for longer periods.  This combined with the comparative lack of ground cover in early spring causes the lizards to be particularly vulnerable to predation at this time.  The majority of the lizard’s time at this time of the year is spent basking or in refuge.  Hunting sorties at this time are short-lived and seldom successful, although opportunities to grab passing food when basking are quickly taken advantage of.  As the year and heat levels progress, less time is spent basking and by early April most mature males having sloughed adopt their gaudy breeding attire.  It is at this point that sand lizards are easily one of the most colourful of British fauna.  Mid April finds male sand lizards especially preoccupied with mating and feeding. Note that mating precludes feeding in that last sentence.  The author grew up on the southern heaths of England and spent many happy hours watching sand lizards.  Some males visibly lost condition due to the vigour’s and stress of breeding and would undoubtedly have benefited from a good feed.

Dorset male taking advantage of the evening sun

Sand lizards, being larger and less wary than their smaller relatives make good study subjects, and the author has been able to witness considerably more sand lizard behaviour than is the case with viviparous lizards.  Male sand lizards whilst preoccupied with patrolling, displaying to rival males and looking for females have in the past chased one another across the author`s walking boots on more than one occasion.  Male sand lizards often meet during the breeding season whilst patrolling overlapping routes.  On such occasions, a series of warning displays are observed.  Rising up on the forelimbs whilst sometimes arching the back and almost always puffing out the neck all combine to make the animal appear larger and more intimidating.  Often the mouth gapes wide open and the tail almost always twitches from side to side.  Invariably the situation progresses no further other than one animal vacating and the “victor” either viewing the departure or following this up by pursuing the retreating animal for a distance (often across the observer’s walking boots!).

Sand and viviparous lizard size comparison

On occasion however, the situation can progress to violence.  If the threat display described previously is not heeded, and a closer approach is made (i.e. to within a few centimetres) then surprisingly loud hissing is employed, no doubt brought about by sudden expulsion of air from the lungs.   Lunging and butting the head and neck region of the opponent then follows, until one or other of the combatants succeeds in grasping the head, neck or base of tail of the other in his jaws and then tossing the animal to one side.  On every occasion the animal, which was thrown to one side, wandered rather drunkenly off.  On three separate occasions however the author has witnessed evenly matched males combating which resulted in a grappling stalemate for about 15 seconds or more, and on at least two occasions visible war wounds on both combatants.On one or two occasions, female sand lizards were in the vicinity and appeared to pay absolutely no attention to the proceedings whatsoever.

Gravid female basking on disgarded timber

Lacerta agilis is an accomplished excavator and does so both to create a safe refuge or burrow and also to bury eggs (oviposit) at sun exposed bare batches of sand.   Sand lizards begin their excavation with shovel-like movements of the head and then follow up with one forearm at a time.  Surprisingly rapid progress is made and the spoil pile becomes down trodden by the lizard and is often used as a basking spot, giving the appearance of a miniature badger hole.  Once the excavation has exceeded body length, it bends to one direction or the other, the occupant tending to sit just around the bend for a good deal of the time.  The burrows are used for thermoregulation on hot summer days, the lizard’s window of activity at this time of year being reduced to an hour or so of basking in the morning and the same in the evening sun.  The rest of the sand lizard’s day is spent thermo regulating in an excavated burrow or abandoned burrow of another species or hunting for invertebrate prey in dense herbage.  Overcast days in summer are far more likely to produce adult sand lizards during the daytime, the animals in such cases taking advantage of heat retained by objects or reflected from marram grass matting etc

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Sand lizard utilising heat retaining moss mat on a bright overcast day

Depending on where-abouts in the country, sand lizards can once again be seen basking at more regular intervals in the cooler autumn air temperatures.  The author has observed sand lizards basking until late September in Dorset but failed to find adult sand lizards at a site in north Wales during optimal weather conditions in late August. Adult sand lizards are often in their subterranean hibernacula when hatchling sand lizards are abroad, which may significantly reduce instances of cannibalism whilst the juveniles are so small.

Diet

The author has witnessed southern sand lizards actively foraging through the floor litter on heathland to disturb litter fauna such as spiders and harvestmen, which are rapidly and effectively snapped up.  The sand lizard is an effective and fast hunter and the author has also witnessed a sand lizard make a rather ambitious but successful launch at a honeybee.  Flies, the winged stage of ants, beetles, bugs, smooth skinned caterpillars, crickets and grasshoppers are all on the sand lizard menu.  Both juvenile viviparous lizards and sand lizards are consumed on occasion.

Breeding

Sand lizard courtship proceedings consist of tail chasing, biting, mouthing and tongue flickering.   The male grasps the female by the head or neck and the two animals entwine tails until the male thrusts one of his hemipeni into the female’s cloaca.  Mating can last for up to half an hour.  All mating observations made by the author were on relatively open ground, which of course meant that the animals were exposed and vulnerable to predation for the time period that they were copulating.  This of course does not necessarily mean that mating does not also occur in cover.  Females often move off if disturbed during the mating process as the author can attest.  The male, still attached, is therefore dragged off in a very undignified manner.

Males range over a far greater geographical area than females and can mate with multiple females.  The same opportunity also presents itself to females when a wandering male enters the home range of a female.

Ovipositing test hole

Gravid females bask at every opportunity to facilitate the development of the eggs.  The females generally stop feeding towards the end of may and begin digging a series of test holes in sun-exposed sand close to vegetation.  From 4 to 12 eggs may be deposited.  Humidity levels are as crucial as temperature levels and years of drought produce few successful hatchings as do wet summers.  From 7 to 12 weeks after ovipostion the juvenile sand lizards begin to emerge, late August to September being the usual time.

Predators

Immediately after hatching the juveniles are extremely vulnerable to predation.  Blinking in the day light after the ordeal of hatching and digging through the sand, hatchling sand lizards often pause before heading for cover and can be picked off by garden birds such as robins, blackbirds and thrushes.  Cannibalism does occur and adders and the rare southern smooth snake (Coronella austriaca) also feed upon sand lizards. The obvious mammalian and avian predators take their toll on sand lizard populations, and common toads will respond to the movement of a passing juvenile sand lizard by snapping it up.  Hedgehogs, mustelids, (weasel family) domestic cats and dogs also predate upon sand lizards.

Longevity

Juvenile sand lizards suffer heavy losses. A sand lizard in the wild state has done well if it reaches 5 – 6 years of age.  Animals in captive situations have the opportunity to reach a greater age of over 10 years.