Reproductive biology

The males of many species are brightly colored, with dominant males developing bright breeding colors. When defending its territory, the lizard displays by turning broadside, lifting its head, and expanding its throat. The flanks also flatten so as to present the most massive, threatening appearance. If the threat display does not deter a rival, an attack follows. The combatants bite each other and shake, but wounds are seldom serious because the head is well-armored.

With the exception of a few European species, all lacer-tids are oviparous, which is surprising as many live in temperate and montane environments where viviparity could be expected to evolve. Most lay small clutches (usually fewer than 10) of soft-shelled eggs in a small chamber dug in moist soil, often beneath a sun-warmed stone. As usual in lizards, the larger species lay more eggs, and in the eyed lizard (Lacerta lepida) this may be up to 20. There is no brood-care behavior. The viviparous lizard of northern Europe (Lacerta vivipara) is one of the few lacertids to give birth to live babies. A small brood of four to 11 young is born from late July to early October after a three to four month gestation. Seven Caucasian lacertids of the genus Darevskia are all-female species. They reproduce by parthenogenesis and result from interspecific hybridization.

Over much of the savannas of the northern part of southern Africa, the Cape rough-scaled lizard (Ichnotropis capensis) and common rough-scaled lizard (I. squamulosa) live together. It is a simple rule in ecology that two species do not inhabit the same niche, as they would compete for the same resources. However, adult and juvenile lizards do not usually compete for the same food, and even if they eat the same species they take different size classes. The two rough-scaled lizards grow to maturity, mate, and lay their eggs within a year, and after reproducing die. Incubation of the eggs takes about two months. During any sixth-month period, one species is represented by adults that mate and lay eggs. At this time the other species' eggs are hatching, and the adults have died after reproducing. There is therefore no competition for food between the adults of one species and the hatchlings of the other species. As these hatchlings grow to maturity, the adults of the first species die, while within the ground their eggs develop. The two "annual" rough-scaled lizards have therefore evolved an elegant rotating solution to living together that minimizes competition.

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