INFORMATION ABOUT LACERTA BILINEATA
I spend a lot of time observing western green lizards, but I'm by no means an expert on lacerta bilineata. So because I want to provide anyone who comes to this site with an interest for these fascinating reptiles with accurate information on the species rather than just my own findings and speculations, what you'll read below is more or less directly copied from French, Italian, English and German Wikipedia pages about lacerta bilineata. In some paragraphs I did use my own descriptions though (for example, the descriptions of adult male and female color patterns are based on my own observations which I can back up with photos). But this page here is supposed to give you only factual information; for my own experiences with the animals and some of my (probably not very scientifically accurate) musings about them just go to the photo blog pages here or select your preferred language for the "about-me" page here: Français - Italiano - English - Deutsch.
The one map below depicting the distribution range of lacerta bilineata and lacerta viridis below is also from Wikipedia (authorship by Christian Fischer). The photos are all from inside and around my garden in Monteggio, Ticino (Switzerland).
Interestingly, the Wiki articles in the different languages differ in some small details and also in the amount of information they offer (the most informative article about this particular lizard is the one in German for those who are interested). An example for some of the differing details would be how the articles don't quite seem to agree on the size/length of the animal: English and German Wiki state that the lizards reach a length of up to 40 cm, while French Wiki only speaks of an average size of 30 cm, and Italian Wiki claims the species reaches up to 45 cm.
From my personal observations I definitely agree with Italian Wiki as I estimated the size of the largest males I encountered in the Malcantone region of Ticino (Switzerland) - which is where I took all the photos on this site - at more then 40 cm. It would appear logical though that there are regional differences in the size of the species. Anyway, in such cases where the information slightly varies across the different articles, I went with a good old compromise (which means here you'll read that the species of lacerta bilineata typically reaches a size of between 30-45 cm).
The genus name Lacerta and the species name bilineata are Latin words respectively meaning “lizard” and “with two lines”, with reference to the pale lines present on the flanks of the young individuals.
FAMILY / SPECIES / DISTRIBUTION
The western green lizard belongs to the family Lacertidae (Wikipedia link for Lacertidae : It; Fr; En; De). This is the family of the wall lizards, true lizards, or sometimes simply lacertas, which are native to Europe, Africa, and Asia. The group includes the genus Lacerta, which contains some of the most commonly seen lizard species in Europe. It is a diverse family with at least 300 species in 39 genera.
The closest relative of the western green lizard is the European green lizard (lacerta viridis; Wikipedia link: It; Fr; En; De) which is more common in southeastern regions of Europe. The two species are not easily distinguished without genetic analysis and get often confused; in fact, they were only recognized as different species as recently as 1991.
The map shows the distribution range for the lacerta bilineata (green) and the lacerta viridis (blue) and the small area (yellow) where a degree of hybridization between the two species occurs (link for the map: Wikipedia).
The lacerta bilineata is native in Andorra, Croatia, France, Germany, Italy, Monaco, Serbia, Slowenia, Spain, and Switzerland. It was introduced in Guernsey and Jersey in the Channel Isles and the United States, and there are also introduced colonies on the south coast of the U.K, notably around Poole Bay in Dorset.
Adult western green lizards reach a length of 30 to 45 centimeters including tail (there may be regional differences regarding the size of the species). The tail may reach up to twice the body length. The average weight is about 35 grams. Males are generally a bit bigger than females, with a slightly bulkier head and body.
With females of the species colors and color patterns can vary greatly and range from dark green and brown to shining emerald green, turquoise and blue and everything in between, even male colors (as you can see in the last image in the gallery below).
Adult males tend to look more alike (though there are variations too), with their back usually a striking yellowish to emerald green interspersed with black dots, a yellow or yellow-green belly and blue face, all of which much more pronounced during mating season (the adult male lizards in the first five pictures in the gallery below are all different individuals, but they all were photographed during mating season when their colors were particularly intense).
As juveniles the lizards are mostly brown with a yellowish green chest and belly. Within a year, as adolescents and sub-adults, they develop white lines or dots on both flanks often in combination with black spots until their eventual color patterns start to shine through (as already mentioned above, those two white lines are also responsible for the species' Latin name "bilineata" which means "two-lined") .
REPRODUCTION, BEHAVIOR, DIET AND LIFE EXPECTANCY
Western green lizards attain sexual maturity at around two years. They are territorial animals; the males fight each other, especially during the mating period, when they are very aggressive towards rivals. The mating ritual is precise, and starts with a bite to the base of the female's tail. The females lay 6 to 25 eggs in a humid and warm site, such as in a decomposing log. The baby lizards hatch after 70 - 100 days depending on the surrounding temperatures and already have a size of 8 - 10 centimeters.
As reptiles, the lizards are ectotherms, meaning their body temperature depends on that of their environment. This, by the way, is also why the best time to observe lacerta bilineata is during the morning hours in spring when the air is still relatively cool, because the animals need to raise their body temperature before they can get into action mode. That's when you'll be able to spot them in places that are exposed to the morning sun, taking extensive sunbaths (which they often also do in the evening). Once they're warm enough to get more active, the lizards go hunting in the grass and in the bushes, where their green color makes them virtually disappear.
Western green lizards are predators and very agile hunters. Like most lizards they're excellent climbers and often hunt in bushes and trees, depending on their habitat, but they can also jump pretty high as you can see in the video clip below (the animal in the clip is an adult female who had seen an insect she desired). They feed on arthropods, mainly large insects, but basically anything they can overwhelm that fits into their mouth ranging from small lizards to baby mice is on their menu. They themselves are prey to cats, foxes, martens, weasels, birds of prey and snakes (and other predators who hunt animals of comparable size).
It is assumed that western green lizards can have a life span of 10 - 15 years, although most individuals don't survive their first year.
The lacerta bilineata's natural habitats are woods, shrubland, open grassland, arable land, and pastureland (most of which can thankfully be found in and around my garden). It is threatened by habitat loss.