Have you often looked at a lizard or turtle and wondered how they could possibly have babies? They aren't very affectionate looking and they don't seem to be very maternal, but like all animals reptiles do reproduce and have some interesting ways that they achieve their goal.
Most reptiles reproduce sexually. However there are some reptiles that have been known to produce asexually. Sexual reproductive activity takes place at the cloaca. This is the opening at the base of their tail where excretory waste is eliminated. Some species do not have copulatory organs and so they will simply press their cloaca together so the male can transfer sperm to the female. The copulatory organs of other reptiles are stored inside the body and only emerge when mating is to occur. Male tortoises and crocodilians both have just a single penis while snakes and some lizards have hemipenes.
Asexual reproductions, also known as parthenogenesis is documented in at least 5 lizard families and 1 snake. There are colonies of lizards that are made of all female lizards. They reproduce by creating one unisexual diploid clone of the mother. There are species of gecko that this is commonly displayed. There has also been several cases of parthenogenesis in the Komodo Dragon.
Sexual behavior in the reptile world is varied and can be quite interesting. Some courtships will take only a few minutes, while some can last for hours. Some lizards will bounce up and down on their front legs as if doing push ups and the skin on their throats will change colors or distend. Some tortoise males will ram into females in order to stimulate ovulation, while other tortoises bite the front feet of the females. Crocodiles and alligators will blow bubbles against the cheek of a female they adore. Some of the mating displays are meant to ward off competitors while at the same time attract the females to them. Alligator males can be heard roaring through the everglades during mating season. The deeper the roar the bigger the male. This serves to alert smaller males to back off, while encouraging the female to come where a big strong male is. Snakes are not as aggressive. In fact it is not unusual to come across a ball of snakes containing more than 100 snakes all writhing together. This is called a nesting ball. In the center is one female and the males all vie to mate with her. She may mate with several males in the ball. This is common among garter snakes, anacondas, and pythons. With other lizards it's all about the head bobbing and color displays. No matter the method it's interesting and sometimes quite amusing to watch the courtship behavior of reptiles.
Most reptiles are oviparous, this means that they lay eggs. Some species will lay large clutches of eggs and then leave to let the young develop and hatch on their own. There is no care given to the young and they are left defenseless. This is commonly seen in sea turtles. Sea turtles will come up on the beach and dig a deep trench in the sand and lay over 30 eggs per clutch, cover them back up and then head back to the sea. However some species will dig a hole and lay only one or two eggs in each place before covering them up and moving on. This helps to ensure the species because if only one nest is found then some of the eggs have a possibility of surviving.
Other species such as crocodiles, pythons and some large tortoises will create a large nest and stay with it, protecting the eggs. In fact pythons have been known to curl around the eggs and flex their muscles to help keep the eggs warm. Once hatched the mother will stay with a young a few days before leaving them to their own devices. Crocodiles and alligators will defend their nest violently and after the young have hatched the mother will take the young in her mouth and bring them to the water's edge to keep them safe. She too will stay with them through the first few days of their life and should they get into danger they make a chirping noise that will bring mom charging to the defense.
Other reptiles are ovoviviparous. This means that the mother reptile keeps the eggs inside her until the moment that the babies are hatched and then she gives birth. This has led to some people thinking that they give live birth but essentially she just keeps the eggs inside until they are able to go freely on their own. There are many species of both snakes and lizards that are ovoviviparous, but no turtles are known to practice this.
Reptile babies are born fully functional and need no real care from their mother. From the moment they hatch they have an egg sac that provides them with enough food to travel a small distance and then can begin eating on their own. Because reptile babies are small it is rare to actually see the young in the wild. Many reptile young will stay as hidden as possible to avoid being snacks for other predators.