Lizards have a fascinating reproductive process that begins with courtship rituals and copulation and ends months later with egg-laying and live births. The length of gestation varies considerably among the over 6,000 species of lizards, but here is an overview of how long lizards carry their young before giving birth or laying eggs.
Gestation Periods in Lizards
Lizards can be divided into two groups based on their reproductive strategies:
Egg-laying (Oviparous) Lizards
- Most lizard species are oviparous, meaning they lay eggs rather than giving live birth.
- For oviparous lizards, the length of pregnancy refers to the time between copulation and egg-laying.
- The gestation period for egg-laying lizards varies from 4-8 weeks depending on the species.
- Some examples:
- Leopard geckos have a gestation of 4-6 weeks before laying 2 eggs.
- Bearded dragons gestate for 4-8 weeks and lay 20-40 eggs.
- Water dragons gestate for 5-7 weeks before laying 10-15 eggs.
Live-Bearing (Viviparous) Lizards
- Around 20% of lizard species give live birth to offspring rather than laying eggs. These lizards are viviparous.
- For live-bearing lizards, pregnancy lasts from the time of copulation until birth.
- Viviparous lizards generally have longer gestation periods of 2-3 months.
- Some examples:
- The common side-blotched lizard is pregnant for 2 months before giving birth to 5-10 young.
- The skink Chalcides chalcides is pregnant for nearly 3 months before birthing 4-12 babies.
- Prehensile-tailed skinks gestate for over 3 months and can birth litters of 12-16 offspring.
Factors Affecting Gestation Length
The length of pregnancy in lizards is influenced by several factors:
- Species: The lizard species determines whether eggs are laid or live young birthed, which greatly impacts gestation length.
- Environmental temperature: Warmer temperatures shorten pregnancy in many lizards. Cooler climates often result in longer gestation periods.
- Maternal body size: Larger female lizards tend to have longer pregnancies before laying larger clutches of eggs. Smaller females gestate for less time and produce fewer eggs or offspring.
- Geographical location: Lizards living in certain environments may have adapted gestation lengths to match seasonal conditions. For example, lizards in cold climates often give birth/lay eggs in spring.
- Maternal age: Older, more experienced female lizards sometimes have longer pregnancies and produce more offspring than young females.
- Maternal health: A healthy lizard with robust fat stores may gestate for a longer period and lay larger clutches than an unhealthy female.
Stages of Pregnancy in Lizards
Lizard pregnancy can be divided into three main stages:
1. Fertilization and Implantation
- Mating and internal fertilization occur through a process called cloacal kissing where male lizards transfer sperm into the female’s cloaca.
- The fertilized eggs (zygotes) migrate to the oviducts and implant into the uterine lining where embryonic development begins.
- Implantation occurs within 24 hours of copulation in most lizard species.
- Once implanted, the embryos grow within eggs or inside the female’s body.
- In egg-laying lizards, calcium is deposited on the eggshells and egg yolks provide nourishment.
- For live-bearing lizards, gas exchange and nutrients are transferred across the placenta to the fetuses.
- The developing offspring become fully formed during this middle gestation period.
3. Birth or Egg-Laying
- Oviparous lizards lay soft-shelled leathery eggs in clutches of 2-40 eggs depending on species. Mothers often remain to incubate eggs.
- Viviparous lizards give birth to independent young through contractions and dilation of the cloaca. Mothers provide no further care.
- Newly emerged offspring are immediately capable of hunting and avoiding predators.
How Long Are Lizards Pregnant? Examples by Species
- Leopard Gecko: 4-6 weeks. Leopard geckos mate in spring after winter brumation. Females lay 2 eggs 30 days after copulation which hatch 2-3 months later.
- Green Anole: 3-4 weeks. These small lizards native to the southeastern US breed April-July. Females lay single-egg clutches every 7-14 days during the breeding season.
- African Fat-Tailed Gecko: 5-6 weeks. These docile pet lizards mate year-round and gestate for about a month and a half before laying 2 eggs. Hatchlings emerge 2-3 months later.
- Eastern Fence Lizard: 4-5 weeks. Abundant in eastern North America, females lay 5-12 eggs in summer after 4-5 weeks’ gestation. Eggs incubate for 6-8 weeks before hatching.
- Bearded Dragon: 4-8 weeks. A popular pet lizard, bearded dragons breed early spring through summer. Females lay 20-40 eggs about a month and a half after mating. Incubation takes two months.
In summary, the length of pregnancy in lizards depends on the species, environment, geography, and maternal attributes. Oviparous lizards gestate for 4-8 weeks between mating and egg-laying. Viviparous lizards are pregnant for 2-3 months from copulation to live birth. Warmer temperatures, larger size, older age, and good health can prolong gestation periods in lizards. Understanding the reproductive cycle of these fascinating reptiles provides insight into their adaptations and life history strategies.
Do pregnant lizards require special care or conditions?
Pregnant lizards might benefit from additional care. Providing a well-balanced diet, suitable temperature, and sufficient hiding spots can help alleviate stress and support their reproductive needs. However, the specific care varies by species, so research your lizard’s requirements to ensure their well-being during pregnancy.
How does temperature impact lizard pregnancy duration?
Temperature can influence the duration of lizard pregnancy. Warmer temperatures often lead to faster development of embryos, potentially shortening the gestation period. Conversely, cooler temperatures might slow down embryo development, resulting in a longer pregnancy duration in some species.
Are there any unique adaptations in pregnant lizard anatomy?
Pregnant lizards may exhibit physiological changes to accommodate pregnancy. Some species develop a distended abdomen to accommodate growing eggs or embryos. In viviparous species, where embryos develop internally, reproductive structures might become more complex to support embryonic growth and development.
How does the number of offspring impact pregnancy length?
The number of offspring can impact pregnancy duration in lizards. Species that carry larger numbers of offspring tend to have shorter gestation periods, as the developmental process for numerous offspring might be more rapid. Conversely, species with fewer offspring may have longer gestation periods.
Are there any known factors that can affect lizard pregnancy duration?
Lizard pregnancy duration can be influenced by various factors. Temperature, maternal health, and food availability can impact embryo development. Evolutionary adaptations specific to each species also play a role in determining pregnancy length. Research into the species’ natural history can provide insights into these influences.