The sand lizard (Lacerta agilis) is a lacertid lizard. There are several subspecies, including L. a. agilis, L. a. argus, and L. a. exigua. The sand lizard is distributed across most of Europe from the southern coast of Britain and across the continent to Lake Baikal in Russia. It does not occur in European Turkey. Its distribution is often patchy. In the northern extremes of the sand lizard's distribution, it survives by inhabiting seaside heathlands, where the ground temperature is elevated by the sun. The sand lizard uses warm sand to thermoregulate itself and to incubate its eggs. Males are known for their bright coloration and aggressive, possessive behaviors when seasonally competing for females. In contrast to other squamates, the sand lizard's mating season is very short. Males choose mates selectively, whereas females mate more indiscriminately. Females usually lay only a single clutch of eggs per year. Sand lizards spend most of their time basking, foraging, or under vegetation. They prefer to live in diverse habitats. They are largely solitary outside of mating season. Male sand lizards typically have larger territories than females, and they will compete with other males when territory overlaps. Females neighbour each other more amicably, occasionally sharing habitats. Sand lizards may live up to ten years. Due to their longevity, they are sometimes prone to inbreeding.
Description
The sand lizard is a sexually dimorphic legged lizard. In northwest Europe, both sexes are characterised by lateral and dorsal strips of ocellated (eye-shaped) markings, which appear as dark patches with pale centres. Colouration varies across their European and Russian range. Males have finer markings than females, and their flanks turn bright green during the spring mating season, fading again in the late summer. Male adults may reach a total body length of 19.3 cm, where female adults may reach 18.5 cm. In the two main western subspecies (L. a. agilis and L. a. argus), the dorsal stripe is thin and interrupted, or not present at all. L. a. argus also includes a plain red or brown-backed phase without any dorsal markings. In these two subspecies, only the flanks of the males turn green in the mating season, but in the eastern subspecies (predominantly L. a. exigua), males can be wholly green, even outside the breeding season. Sand lizards can self-amputate their tails as a defence mechanism. This ability is called autotomy. In males, the bright green genital coloration has been shown to be brighter depending on body mass and fighting ability. Males with brighter colors were more likely to initiate aggressive behaviors and win fights, which generally leads to them having a higher mating success. Females are more of a grey to brown color and can be seen with large bulging bellies full of eggs, from May to August. Sand lizards can live for over ten years, with their average lifespan lasting between 5–6 years.
Habitat and distribution
The sand lizard can be found in a variety of habitats. They prefer dry habitats, such as outcrops, fields, hills, beaches, heathland, sand dunes, and rock gardens. While in continental Europe the sand lizard has a wide variety of habitat, in colder places like Great Britain they depend on sand to incubate their eggs and such are restricted to coastal habitats. Male sand lizards have home ranges with an extremely high amount of overlap; however, female sand lizards have much smaller home ranges (generally less than 100 meters squared) that neighbor each other, or they will even share burrows or basking areas with each other. They highly prefer and are much more active in areas with a wide variety of structural characteristics. This can create different temperature micro areas that they are able to move between depending on their needs.
Behavior
General activity Sand lizards spend extended periods of the day after emerging on long basking sessions. They occasionally take breaks to forage for resources. They also spend a considerable amount of time simply doing normal activity in areas under concealed vegetation. Under poor weather conditions, sand lizards emerge from resting locations later and bask less often throughout the day. Sand lizards most frequently bask on logs. This is most likely due to its absorption and slow release of heat radiation as well as providing a vantage point to spot potential predators and prey. They very rarely share basking sites with other lizards. Male sand lizards especially avoid sharing basking sites with each other, and are found only occasionally sharing with females. They avoid basking on open sand or soil and prefer to use vegetation if they bask on the ground. They thermoregulate themselves by moving between areas of high and low insolation.
Mate selection In general, female mate choice in organisms is more selective than male mate choice. This is due to the fact that females generally have to invest more time and resources into offspring than males, who are under less selective pressures due to their low parental investment. Generally females will simply reject male attempts at mating outside of their receptive mating period, doing so through a unique head bobbing behavior. However, during their period of receptivity, females have been known to not discriminate against different males and do not reject them besides when they are outside of this period. Male sand lizards have been shown to highly prefer larger females when selecting mates, but they are still willing to mate with smaller females if the opportunity presents itself. It was observed that some males that were too small for the large females they attempted to court had troubles gripping females with their jaws during copulation due to their small size. This may be one constricting factor in their choice of mate.
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