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The sand lizard ( Lacerta agilis) is a Lacertidae 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 United Kingdom and across the continent to Lake Baikal in Russia.M., Smith (1969). The British Amphibians and Reptiles. Collins, London, UK. 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 , where the ground temperature is elevated by the sun. The sand lizard uses warm sand to Thermoregulation itself and to Egg incubation its eggs.
Males are known for their bright coloration and aggressive, possessive behaviors when seasonally competing for females. In contrast to other Squamata, the sand lizard's mating season is very short. Males choose mates selectively, whereas females mate more indiscriminately. Females usually only lay 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.
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.
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.
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.
The female sand lizard lays in loose sand in a sunny location, leaving them to be incubated by the warmth of the ground.Olsson, Mats (1988-01-01). "Ecology of a Swedish population of the sand lizard (Lacerta agilis) - a preliminary report". Mertensiella. 1: 86–91.
Female sand lizards usually only lay a single clutch each year and clutch sizes that range between six and 15 eggs in a single one. However, there is a lot of variation in the time of year when females end up laying their eggs. But generally a single female sand lizard has a relatively consistent egg laying timing from year-to-year, with the first ones to do so generally being larger, more physically fit females. These early clutches ended up producing offspring that were larger, more successful, and had higher survival rates. Generally offspring from earlier clutches were higher quality offspring.
When female sand lizards produce larger clutch sizes, the size of each individual offspring in it has been observed to decrease. On the opposite side, smaller clutch sizes had fewer, but larger, offspring. When food resources were increased so it was not a limiting factor, clutch size increased significantly, so it is likely that sand lizards produce clutch sizes with different offspring sizes based on resource availability. The other factor that contributes is the physical constraints of the space available to lay their clutches in.
Natural malformed offspring have been observed in sand lizards most likely due to close kin inbreeding defects. Because of their relatively long lifespan and male polygynous mating, there is a decent chance of inbreeding occurring during their lifespan. Inbreeding has been seen to cause malformations in sand lizards with studies in laboratory settings mirroring the deformations seen naturally in the wild.
Sand lizard locomotor performance, agility, and speed is related to their ability to avoid predators (as well as foraging efficiency). Like many lizards, sand lizards are able to separate their tail from the rest of their body in order to escape predators. Sand lizards with autotomy were able to run faster and as a result were better at avoiding predators that were chasing them. These tails do not regrow past 80% the original length after autotomy.
Sand lizards are a frequent carrier of common ticks which are a great risk to the health of the lizards, especially males during breeding seasons when they have great mobility. Males with larger home territory ranges were also subject to carrying even greater loads of parasites. Trematodes, metacercariae, cestode larva, nematodes, nematode larvae and acarines are all examples of parasites that inhabit the alimentary tract of this lizard.
When male sand lizards compete over females, they perform ritualistic displays that often escalate into aggressive behaviors and actual combat. Males raise themselves up on all four limbs and turn over to intimidate their opponents, one may back down at this stage but if not, the two can begin fighting actual combat. They mainly attack through biting each other and aim at the heads or other vulnerable spots. Occasionally, even extremely deep cuts into jaw muscles and tissues were observed. Generally, equally sized males will have longer fights than two males with differing sizes; however, males fighting intruders in their own areas of residence did not win significantly more than intruders.
If male sand lizards engage in a fight with another multiple times, they will consider them a rival. However, subsequent aggressive interactions beyond the first one tend to be much shorter on average than the first encounter between the two. This is most likely because they are able to individually recognize others and the result of the fight between two rivals will most likely be similar to the first, so they are able to predict the outcome and end their battle early.
Sand lizard mating seasons are very short, lasting only 17 days of the entire year. Generally males are only able to mate with an absolute maximum of six different females during this time period and because a single mating guarding session can take up to 18% of the entire mating season.
Because of this, a several day time commitment means the investment male sand lizards put into mating is incredibly high and as a result males can begin to develop selective preferences for certain females. Because female sand lizards are often found close together in groups, males have more choices and opportunities to choose a mate depending on their individual characteristics.
The sand lizard is facing multiple threats throughout its range, including habitat destruction, habitat degradation, habitat fragmentation, lack of habitat management, climate change and inappropriate habitat management. Although the sand lizard is under strict protection in the UK, there are still actions needed to be taken, including habitat protection, habitat management, species protection, species management, distribution surveys, population and conservation status monitoring, scientific research, and public awareness.Russell, Liam (December 2012). "THE CONSERVATION AND LANDSCAPE GENETICS OF THE SAND LIZARD Lacerta agilis"
Efforts in the UK have been made to protect and conserve their habitats because the sand lizard is one of only six reptile species found in Britain. Lizard populations were analyzed and their habitats were studied and specific recommendations were made for maintaining the quality of the environments so sand lizards can continue to inhabit those regions.
In Sweden, the sand lizard is also considered threatened and is managed by a national protection plan. Populations are highly fragmented. This is thought to have led to an increase in inbreeding and low genetic diversity; as of 2017, the Swedish sand lizard populations decreasing by around 20-40% in the previous approximately 20 years. Swedish sand lizards are generally found around the coast where sparsely vegetative habitats are more common. However, there are also populations as far north as Värmlands and Dalarna County; despite the species' name sand, does not always appear to be a requirement for populations.
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