How is reproduction in turtles?

Here we will compare the reproduction process in land turtle reptiles, such as the Hermann’s turtle (Testudo Hermanni) and the Greek turtle (Testudo graeca), and reproduction in sea turtles.

How to differentiate a male from a female?

First of all, here are some keys to differentiate a male turtle from a female turtle:
The female generally has a flat plastron (belly) and a small tail while the male has a hollow plastron and a strong and long tail. This morphological distinction is generally made from 5 to 6 years old. Before, the determination of the sex can pass by the observation of the behavior of the animal, the males being more aggressive, attacking their congeners, whereas the females are calm and sociable.

Age of sexual maturity

In the wild, land turtles begin to reproduce at around 12 to 14 years of age. In captivity, sexual maturity is advanced to 8 to 10 years. Sexual maturity is in fact more determined by the size than by the age of the turtle. Thus, sexual maturity is reached in the male when the plastron measures 11 cm, while the female reaches its maturity when the plastron measures 14 cm.

The age of sexual maturity of sea turtles is more difficult to estimate, since these turtles reproduce only at sea. Nevertheless, scientists estimate sexual maturity at about 13 to 14 years of age.

Season of reproduction

The reproduction of land turtles begins after the winter, at the end of hibernation, around the month of March. The female has the possibility of mating with several males in the same season. She can also keep the male turtle’s sperm intact inside her reproductive tract. As a result, the female can lay fertilized eggs during the second season, even without having mated. The male usually shows interest in the females until late May – mid June. Reproduction can start again in September or October, depending on the climate. Note that turtles generally start to reproduce before they even start eating again after hibernation!

For the sea turtle, the nesting season depends on the turtle species but also on the nesting beach.

For the land turtles, after hibernation, the female generally exposes herself to the sun to warm up. On the other hand, the male is very agitated. It is always the male who triggers the mating. He looks for the female by touching her with the tip of his nose. Then he nods his head in front of the female several times before moving her forward by hitting her shell. Then, he bites her front and back legs successively and slides her tail under her carapace. It may be necessary for the male to repeat these operations several times. Generally, shell hits and leg bites are harmless to the female. On the other hand, fights between males for the same female can be very violent. This aggressiveness can lead to injuries. Thus, you must be very careful if you introduce a new male during the mating period. It may sometimes be necessary to separate the fighting males. After mating, the male will calm down and start to eat.

Sea turtle mating takes place in the water and is similar to that of the land turtle. The male turtle clings to the shell of the female with his two claws on the front legs. It is important to know that the female does not mate every year but generally every 3 to 4 years!

Egg-laying

Egg laying by land turtles occurs 1 to 2 months after fertilization. It is preceded by warning signs. The female “visits” hypothetical places of laying. Before digging her nest, she often behaves like a male and climbs on other congeners. Then she starts to make a hole of 6 to 10 cm with her hind legs, in a sunny and slightly humid place. She usually lays her eggs in the late morning or late evening. When it is time to lay eggs, it usually stands with its back to the sun, its tail stops and the eggs start to come out. The eggs are oval, white, 2 to 3 cm long. The shell is hard, each egg weighs about fifteen grams. There are usually 6 eggs per laying (and 2 to 3 layings per year). Laying lasts several hours (usually between 2 and 4 hours). When the laying is finished, the turtle, exhausted, covers the hole with soil and adds twigs and leaves. The turtle must not be disturbed during the laying process, as it may interrupt the process. Also be careful of domestic animals (dogs and cats) and wild predators, which could eat the eggs. In captivity, it is important to ensure that the turtle can find a suitable place to lay its eggs. Otherwise, egg retention could occur and cause serious health problems for the turtle.

Sea turtles lay their eggs at the birthplace of the female turtle, on a beach. Usually, the female comes out of the water at night (to avoid too much heat) and goes up on the beach. She digs a hole with her front legs, lays eggs in it and then closes the hole. Egg laying can last up to 3 hours. She then returns to the sea. The turtle usually lays 150 eggs in one clutch! However, many eggs or newborns will be devoured by predators (seagulls, etc). The turtle can lay several times in the same season (usually between 3 to 5 times), but always with a minimum 15 days interval. Depending on the species of turtle considered, the female will go to the beach to lay eggs alone, or several hundred turtles will come to lay eggs at the same time, or even several thousands: this phenomenon is called “arribada” and usually lasts one week.

Incubation of eggs

For ground turtles, the incubation temperature should be between 27 and 33 °C. If the temperature is not sufficient, an incubator should be used. It should be noted that the incubation temperature determines the sex of the newborn: at 27 – 29°C the embryos will be male, at 30-31°C there will be half male and half female, at 31-33°C there will be only females. Incubation lasts 75 – 90 days.

For sea turtles, incubation usually lasts 2 months. Similarly, the sex of the newborns depends on the temperature of incubation: below 29°C, the babies will be male, above it will be female, and in between there will be half male half female.

Hatching and first aid for newborns

For land turtles, hatching eggs can take several hours, usually 1 to 3 days. Babies have a horny tooth at the end of their beak that allows them to pierce the shell to come out. During the hatching process, there is no need to help the baby out of the egg. Indeed, the small ones remain in the shell the time that the yolk sac (which contains the energy reserves) is resorbed. The hatching should therefore not be rushed. The baby turtle leaves huddled up of its egg. It has a navel on the plastron, a scar which will disappear thereafter. When the little one is completely out, he takes a bath. In captivity, it is thus necessary to install a tank containing a little warm water to allow the baby to drink for 3 to 5 minutes. Afterwards, it usually sinks into the ground. In captivity, there are generally two different tanks: the incubator and the nursery, integrated 3 days after birth. It is generally at this time that the baby turtle begins to feed. Like its parents, it is herbivorous, but feeds on softer shoots (dandelion, clover…). In captivity, you can reduce the plants into small pieces to make their task easier.

All sea turtle eggs hatch at the same time, and the newborns immediately head to the sea, where they begin an active swim for several days. After about a week, they become pelagic, meaning they stop swimming actively, to let themselves be carried by the currents and look for food. Then the youngsters settle down.