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Common or Viviparous lizard
Zootoca vivipara
General description
The common or viviparous lizard is an incredibly varied species in terms of colouration. These variations occur right across the animal’s extensive range. There are however no isolated “races” of the species, hence an individual animal from South Wales can appear the same as an example from Asia.
The most commonly seen ground colouration of common lizards in the area of West Glamorgan is generally brown varying from darker shades through a lighter straw brown to green as well as all shades between. Laid over the ground colouration is a complex pattern of stripes, speckles and lines which also vary greatly in intensity. Entirely black or melanistic individuals occur at sites in West Glamorgan as well as partially melanistic animals. Furthermore another mutation is encountered with a fair degree of regularity at sites in West Glamorgan and the surrounding area which exhibit a considerably reduced pattern to the extent where some individuals display no patterning such as stripes and speckles at all.
This gravid, heavily patterned but typically coloured female viviparous lizard clearly displays a vertebral line and dark sides. The tail is regenerated.
Another gravid female from the same site as the previous animal displaying reduced patternisation, possibily hypo-melanism.
Melanistic female dorsal and ventral views.
Partially melanistic male compared.
Ventral or belly colouration is generally yellow to bright orange in the case of males with an accumulation of black speckles or spots. In contrast, females have paler pattern-less bellies often being either grey or a muted pastel like shade of orange or peach. Common lizards tend to reach a maximum of around 180mm (6 or 7 inches) in total. The tail is long and tapering and on occasion can account for two thirds of the overall length.
Adult male - Image by John Wilkinson
Sexing Common Lizards
In general terms, males exhibit broken lines and speckled patterning across the dorsum or back of the animal. These speckles can on occasion take on the form of an intermittent vertebral stripe (running the course of the vertebrae). Females nearly always exhibit a more clearly defined vertebral stripe running the length of the body, although on occasion this can be slightly broken which can make differentiation of the sexes by using this method alone unreliable.
Males tend to have larger heads proportionally when compared with females and upon closer examination exhibit a noticeable bulge at the base of the tail which houses the hemipenis. This bulge is absent in the case of females. As mentioned previously the ventral colouration differs noticeably between the sexes, as well as body proportions. Males, as well as having slightly larger heads also display a proportionately shorter body length and greater tail length when compared with females. Presumably the greater proportionate body length of the female allows greater scope to accommodate developing young. For example, compare an adult male, in this instance, of an overall length of 156mm compared with an adult female of an overall length of 151mm. Although the overall length of the male in this example is greater, when we compare body proportions the female in question has a greater snout to vent length (65mm) than the male (55mm). Contrastingly, the male has a noticeably greater tail length (101mm) when compared to the female’s (86mm).
Habitat
Zootoca vivipara inhabit a wide range of habitats in the area of West Glamorgan. Heathland, particularly wet heathland is widely considered to be the ideal habitat for common lizards and the species occurs at mixed heathland sites in the Neath, Pellenna, Pontardawe and Gower area. However, heathland is far from the only habitat at which you are likely to see common lizards.
The key to suitable common lizard habitat is a complex and varied vegetation structure which is exposed to sunlight for the greater proportion of the day. Acid grasslands, scrub, and the edge of bramble and gorse when combined with rank grass are all likely habitat. South facing hedgerows and elevated banks are often inhabited by common lizards as are roadside verges and railway embankments which also serve as important corridors to connect populations.
Vegetated coastal cliff paths often support large colonies of common lizards as can sand dune systems with both mature and new growth marram grass, the lizards often basking on the dead sun exposed marram thatch.
Wetland habitats such as fens, canal banks and wet heaths are also ideal for common lizards. In instances where wetlands are furnished with wooden boardwalks for access purposes, common lizards often take advantage of the edge of the boardwalk to bask. Seldom any more than a body’s length away from cover, and often partially shielded by overhanging grass, reeds or other vegetation, such prime basking spots are often occupied by the lizards in groups of two or three animals. Lizards disturbed or pursued at such sites have been observed by the author to drop straight into the water below and swim away on numerous occasions.
An often overlooked but very significant habitat for the common lizard and many other reptile species are post industrial or “Brownfield” sites. Nature soon gains a hold on such places if left for long enough and banks and heaps of clinker, rubble and hardcore with areas of grasses and brambles interspersed among them provide well drained sanctuary for the lizards to flee to if pursued. Common lizards thrive at such sites feeding upon the diversity of invertebrates that the plant life attracts and basking just as confidently on discarded pieces of metal, UPVC window frames, plastic and concrete as they do on more natural substances such as logs or rocks. Discarded tyres are particularly sought after basking spots, the black rubber retaining heat for a good deal of time, long after the sun has been obscured by cloud.
Behaviour
Common lizards enter underground frost free subterranean hibernacula in mid October and re-emerge around mid to late march. The males are generally first to emerge, the females appearing a week or two later. One explanation for this could possibly be due to the recently emerged male’s sperm not yet being viable. Hence a mating when the males have been abroad and active for a period would be more likely to produce young.
The species can shed the tail in segments or in its entirety if necessary as a means of escaping predators. The ability to do so is known as autotomy. In the event of an animal shedding its tail, the appendage will regenerate but the replacement is never as elegant as the original and tends to taper more suddenly. Animals with recently truncated tails are often encountered. When captured, the tail is often lashed from side to side, no doubt to distract a predator’s attention towards the movement where-upon the animal can shed the tail and make it’s escape whilst the predator occupies itself with the tail which can remain animated for a full minute or on occasion longer.
Sitting still and observing common lizards at an appropriate site can be very rewarding. Even if disturbed from basking, an animal will often return to it’s basking spot, when it can be possible to sit still and watch the lizard without it even being aware of the observer’s presence. The author has witnessed feeding and mating behaviour by doing so on many an occasion even to the extent where particularly bold animals have travelled across or even basked upon the author’s walking boots.
A common lizard’s day begins with basking, as early as 6am during the height of summer. As it unfolds the lizard’s day is broken up into periods of basking interspersed with spells of active hunting or searching for a mate. Such patrols are often circular in route, enabling the lizard to return to a favoured basking spot between patrols. The length of basking period is dictated by the weather and air temperature and can also be dependant on the animal’s condition. Gravid (impregnated) females tend to bask for longer periods to aid the development of the unborn young. Early in the morning and early in the year when the air temperature is considerably cooler, basking lizards can be surprisingly sluggish, even on occasion dragging their limbs until they are sufficiently warmed to go on the first patrol of the day. At such a time of the year, initial patrols are invariably short lived due to the need to return to the basking site relatively quickly as well as the likelihood that the hunting patrol would be unsuccessful because of lesser densities of invertebrates in early spring when compared to summer, when the time length of the patrols increase significantly.
A common lizard on the move in dense cover during one of its patrols will climb and move through vegetation both slowly and deliberately, flickering its tongue constantly. In contrast, the same animal when observed traversing open spaces will move at a speedier pace, due to the risk of exposure as well as a decreased likelihood of successfully finding prey items when compared with when doing the same in cover. However the author has observed common lizards whilst basking on the timber construction of a boardwalk stimulated by the movement of a harvestman* attempting to cross the open space of the boardwalk, seize the opportunity, leave the basking spot and advance towards the potential prey with a series of short spurts, checking around it as it does so. The prey is then seized with a lunge and shaken vigorously from side to side, the lizard’s head at a slight angle so causing the prey to meet with the hard surface of the boardwalk with some force, whilst also seemingly wiping it’s jaws on the hard surface perhaps in an attempt to remove the harvestman’s legs. On occasion during such situations the prey is largely consumed on the spot but more often than not the lizard retreats to cover with its prize. In the case of long legged prey such as a harvestman, the legs are rarely if ever consumed.
The common lizard’s day ends as it started with a period of basking so catching the remains of the evening sun where possible, often at as late an hour as 7pm during mid summer, before retiring beneath a flat stone, log pile, crack, crevice or abandoned animal burrow. The lizards also use these same retreats during the daytime if weather conditions are too cold, hot or wet as well as to seek refuge if pursued by a predator.
Diet
During late spring and the duration of summer, the common lizard’s habitat is densely stocked with an abundant and varied invertebrate menu. It would appear that much like in the case of people, individuals express preferences. For example, a few individuals will eagerly pounce on a stranded earthworm of suitable size. A greater number however will ignore earthworms. The author has observed common lizards feeding upon smaller spiders of various kinds, craneflies and other two winged flies, harvestmen, grass hoppers, leaf hoppers, shield bugs and aphids of various kinds. All of the above prey items are actively searched for. The observations of other’s have revealed that smooth skinned butterfly and moth larvae are also taken, as well as on occasion small snail species, four winged flies such as bees and the winged stages of ants, smaller centipede and beetle species. Many of the instances of common lizards feeding upon this second list of prey items were observed under captive conditions, which must be taken in to account.
Breeding
Male common lizards exhibit a degree of posturing and aggression a few weeks after emergence from hibernation. Such displays would appear to be not so prominent in common lizard society as is the case with regard to the sand lizard (Lacerta agilis) for example. Fighting can and does occur, but generally such disputes are settled after some grabbing with the jaws by the loser vacating the scene pursued for a short distance by the victor.
A female common lizard entering the domain of a male during April and May will invariably be pursued. The male will seize hold of the female with his jaws and if the female is receptive, the male will align his body with that of the female until the two animal’s vents meet, whereupon the male will insert one of his hemipeni. Copulation usually lasts for around 10 to 20 minutes. The female will more than likely repeat the process and with more than one male.
Female common lizards remain gravid for a three month period, basking for increased periods of time to further the growth of the developing embryos. The common lizard is “viviparous”, and produces live young as opposed to the more usual reproductive method of laying eggs as in the majority of lizard species. Normally during July, from 3 to as many as 11 young are deposited in an egg sac which bursts normally during birth or shortly afterwards. The fully independent new born young appear to be black, but the majority are in fact a very dark olive green ground colour with very closely marked black patterning. Within a few weeks, the majority of the young are a distinct coppery hue, and the markings become more apparent and separated.
Predators
The common lizard is on the menu for a wide range of predators. Juveniles fall prey to wood ants, and familiar garden bird species such as blackbirds. Foxes and badgers may snuffle them out of their retreats, and no doubt stoats, weasels, otters, mink and polecats will tackle them if chanced upon. Kestrels, buzzards and possibly corvids (crow family) no doubt are occasional predators along with pheasants and domestic cats and dogs. Rodents will gnaw and consume torpid lizards if they are discovered and the common lizard is also a favourite prey item of the adder at sites in West Glamorgan. Both the common frog and common toad respond to movement as a feeding stimulus and will no doubt consume immature common lizards if the opportunity presents itself.
Longevity
Common lizards, despite being such nimble, swift and agile creatures are heavily predated; hence the law of averages dictates that individuals are likely to have relatively short lives. Colonies present at sites close to suburbia for example, with high numbers of domestic cats likely to be present, commonly include high numbers of animals of all ages that have regenerated tails with individuals displaying recently truncated tails occurring with regularity. These individuals are obviously survivors of predatory attacks. It would not be unreasonable then to assume that a sizeable proportion of the population do not evade capture.
In contrast, Zootoca vivipara colonies living in more pristine habitat have to cope with significantly lesser densities of predators than at sites with numbers of domestic cats present and adults with “unspoilt” tails are seen with a degree of regularity. Opportunities at such colonies for a small percentage of individuals to achieve some degree of longevity therefore do present themselves. There is a substantiated record of an animal reaching twelve years of age.
*Harvestmen; Opiliones, small bodied eight legged relations of spiders sometimes referred to as “daddy long legs”
