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Viviparous lizard

life science Maturity 5-7 Next article →

The viviparous lizard, also known as the common lizard (Zootoca vivipara), is a remarkable Eurasian reptile.

Common Viviparous Lizard (Zootoca vivipara) (6161781876)
Common Viviparous Lizard (Zootoca vivipara) (6161781876)

It holds the record for the largest distribution of any terrestrial lizard species in the world. This lizard can survive in much more varied climates than most other reptiles. It lives in environments ranging from the British Isles to Japan. It even thrives in subarctic regions. The species is named for its ability to be viviparous. This means it can give birth to live young.

Zootoca vivipara Russia male and female 01
Zootoca vivipara Russia male and female 01

However, some populations are oviparous, meaning they lay eggs instead.

To survive in cold climates, the lizard uses a process called thermoregulation. This is the active control of body temperature to maintain thermal homeostasis. Most animals in extreme cold use thermoconformity, where they simply adapt to the temperature. The viviparous lizard instead uses behaviors like basking in the sun to stay warm. In the harshest winters, it uses a "supercooled" state. This allows the lizard to survive in temperatures as low as -10°C. If temperatures drop further, the lizard can actually freeze solid. It may remain frozen for two months until it thaws out.

It often finds warmth in microhabitats near unfrozen groundwater.

There are distinct differences between male and female lizards, known as sexual dimorphism.

Zootoca vivipara LC0273
Zootoca vivipara LC0273

Males often have larger heads and more colorful undersides. Their bellies may show bright shades of yellow, orange, green, or blue. Males also typically have spots along their backs. Females usually have darker stripes on their sides and backs. Females also exhibit colour polymorphism more often than males. Their ventral coloration can range from pale yellow to bright orange. Researchers like Vercken et al. found this color variation is caused by social cues. This relates to patterns of sex allocation and reproduction.

Reproduction in this species is complex and involves different biological strategies. The ability to switch between laying eggs and live birth is a major focus of study. Some scientists believe viviparity evolved from oviparity only once. However, researcher Yann Surget-Groba suggests it may have evolved multiple times across different clades. He also suggests that reverting to egg-laying is not as rare as previously thought. In the Italian Alps, some populations are so different they might be separate species. These populations are reproductively isolated from one another. If they do hybridize in a lab, the embryos often show malformations.

Historically, the classification of this lizard has changed due to new research. It was once part of the genus Lacerta. In 2007, researchers Arnold, Arribas, and Carranza split Lacerta into nine different genera. This placed the common lizard into its own genus, Zootoca. This change helped scientists better understand the specific evolutionary path of the species. Understanding these taxonomic shifts helps us track how different reptile groups branched out over millions of years.

As an exclusively insectivorous predator, the lizard plays a specific role in its ecosystem.

Zootoca vivipara male front leg
Zootoca vivipara male front leg

It hunts flies, spiders, and various other insects. Its diet includes moth larvae, mealworms, and hemipterans like cicadas. Interestingly, the lizard's diet affects its health regarding parasites. Studies show that more carnivorous individuals have less diverse populations of parasitic helminths. These helminths are small parasitic worms. Larger lizards tend to carry a greater number of these parasites.

Zootoca vivipara male hind leg
Zootoca vivipara male hind leg

The lizard must also avoid many predators, including birds, snakes, and foxes.

The life of a viviparous lizard is defined by its incredible hardiness. Most individuals live for about 5 to 6 years. They reach sexual maturity during their second year of life. Male success in the wild is often tied to physical traits. Larger heads are a result of sexual selection. Males with larger heads are more successful in mating and male-male aggressive encounters. They also tend to reproduce more frequently during a single season. This combination of physical strength and environmental adaptation makes them a highly successful reptile.

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🖼️ Images & Media (6)
File:Common Viviparous Lizard (Zootoca vivipara) (6161781876).jpg
Common Viviparous Lizard (Zootoca...
File:Zootoca vivipara male front leg.jpg
Zootoca vivipara male front leg.jpg
File:Zootoca vivipara male hind leg.jpg
Zootoca vivipara male hind leg.jpg
File:Zootoca vivipara Russia male and female 01.jpg
Zootoca vivipara Russia male and female 01.jpg
File:Zootoca vivipara LC0273.jpg
Zootoca vivipara LC0273.jpg
Arusisalik Zootoca vivipara.ogv
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