[7] Studies show that the more carnivorous an individual is (the more insects they eat), the less diverse the population of parasitic helminths that infest the lizards.

[7] Zootoca vivipara lives in very cold climates, yet participates in normal thermoregulation instead of thermoconformity.

These hypothesis test for coloration due to thermoregulation, predator avoidance, and social cues, specifically sexual reproduction.

Through an experiment conducted by Vercken et al., colour polymorphism in viviparous lizard is caused by social cues, rather than the other hypotheses.

More specifically, the ventral coloration that is seen in female lizards is associated with patterns of sexual reproduction and sex allocation.

[citation needed] Additionally, males have been found to have larger heads than their female counterparts, and this trait appears to be sexually selected for.

[6] Characteristic behaviors of the species includes tongue flicking in the presence of a predator and female-female aggression that seems to be mediated by the colour of their side stripe.

[3] Z. vivipara is terrestrial, so they spend most of their time on the ground, though they do occasionally visit sites of higher elevation.

[3] The size of an individual lizard's home range is also dependent on population density and the presence of prey.

[7] Their diet consists of flies, spiders, and various other insects, including hemipterans (such as cicadas), moth larvae, and mealworms.

[16] Predators of this species include birds of prey, crows, snakes, shrikes, hedgehogs, shrews, foxes, and domestic cats.

This refers to its ability to give birth to live young, although the lizards are also able to lay eggs.

They also argue that a reversion to oviparity is not as rare as once believed, but has occurred 2 to 3 times in the history of the species.

[19] Some research in the Italian alps has suggested that distinct populations of oviparous and viviparous Z. vivipara should be considered separate species.

Cornetti et al. (2015) identified that viviparous and oviparous subpopulations in contact with each other in the Italian alps are reproductively isolated.

[20] Hybridization between viviparous and oviparous individuals of Z. vivipara leads to embryonic malformations in the laboratory.

[6] This aggression and interaction is centered around available mates, so males with smaller heads have significantly less access to females for reproduction.

[25] The first is that Z. vivipara has remarkable behaviors to combat the cold, and there are geological phenomena in their distribution that maintains their habitats at a temperature that the species can survive in.

These lizards have exceptional hardiness to the cold, which allows them to hibernate in upper soil layers in temperatures as low as −10 °C (14 °F).

This cold hardiness along with the favorable hydrogeological conditions of groundwater-warmed soil habitats allows for the wide distribution of lizards throughout the palearctic.

[26] The colour polymorphism of female Z. vivipara has not been thoroughly studied in past years, regardless of the extensive research done on the species itself.

[27] These factors cause the lizards to vary in terms of their fitness (clutch size, sex ratio, hatching success).

Additionally, female lizards disperse through habitats based on the frequency of colour types that are already present in the population.

Yellow morphs remain in the population due to their large clutch size, which causes an increased frequency of those females.

[9] Selection favors the yellow morph because of the ability to produce large clutch sizes, which increases the female's fitness.