Snakes reproduce in different ways and at different times, even within a species.
Telling sexes apart is not always easy. With Boomslang, except for most of the Eastern and Western Cape, males are usually green and females brown, but not always. In many other snakes, like the Puff Adder, males have a much longer tail than females do but this does not apply to all snakes. Herpetologists use metal probes that are inserted into the sexual cavities toward the tail, and depending on how deep the probe penetrates, the sex of the snake can be accurately established. In males, the probe usually penetrates more than twelve subcaudal scales and in females, less than three. In some snakes, like the Southern African Python, the females get much longer and bulkier than males. In many cobras, the males get a lot larger and bulkier than females.
Most snakes mate in early spring and do not generally move around in pairs. When ready to mate, female snakes emit pheromones to attract males and several males may follow a single female. Males of some species, like the Black Mamba, Puff Adder or Rhombic Night Adder, may engage in male combat. It is usually a bit of a wrestling match with the snakes intertwining as the one male tries to push the other to the ground and tire it out. Such battles can last for more than half an hour and the winner gets to mate with the female. During male combat, snakes do not necessarily bite one another, not that it really matters as snakes are immune to their own venom. Mole snakes, however, are quite vicious during male combat and bite one another, leaving gaping wounds. These wounds heal quickly and have virtually no effect on the snakes.
Male combat in Black mambas.
Male snakes have paired sexual organs called hemipenes. These hemipenes, when everted, can be rather complex in appearance with blobs, hooks, spines or spurs. This is for the hemipenis to attach when inserted into the female during mating. Hemipenes are so complex in structure that taxonomists have used their appearance do distinguish a species, when describing newly discovered species.
During copulation, the male snake usually mounts the female while flickering his tongue and will twist his tail beneath that of the female for a single hemipenis to protrude and enter the cloaca of the female. Copulation may last several hours or even days. After copulation, the male pulls his hemipenis back into his tail region using a retractor muscle.
Female snakes, once mated, can store sperm, enabling her to produce viable young for several years in succession, without mating again. Some snakes produce two or three clutches of eggs a year, while others may only reproduce every second year. Like females, males can also store sperm and do so in the ducts of the testes.
One of our sakes, the Flowerpot Snake (also called Brahminy Blind Snake) that was introduced from India and South-east Asia, is an all-female population and produces viable eggs without mating, the young are all female and genetically identical. This phenomenon is called parthenogenesis.
The all-female species, the Flowerpot Snake or Brahminy Blind Snake (Indotyphlops braminus)
Most of our snakes are egg-laying (oviparous). Snake eggs are soft and leathery and are usually laid underground or in a hollow log or under large rocks. Most of our snakes lay their eggs and abandon them, and the eggs will hatch in 6 – 36 weeks, depending on the species and incubation temperature.
An Olive Snake (Lycodonomorphus inornatus) dropping eggs. Photo Nick Evans.
There are exceptions. Both the Southern African Python and Spotted Skaapsteker remain with their eggs throughout incubation and protect them. Spotted Skaapstekers usually lay their eggs under flattish rocks and several females may lay their eggs in communal laying sites. Their eggs seem to be partially incubated when laid, as they hatch within about six weeks.
The Southern African Python lays its eggs in holes in the ground, favouring Aardvark and porcupine holes. Females may return to the same laying site year after year. Breeding females go very dark in the breeding season and will coil around their eggs protecting them. A female will lose around 38% of her body mass when laying and will refuse food for the three months it takes the eggs to hatch. During this period, she will often bask at the burrow entrance but is quick to disappear down the burrow if disturbed. When the eggs hatch, the young remain with the female for a few days and usually disperse after their first shed.
When snake eggs are ready to hatch, hatchlings have a toothlike projection on the nose called an egg tooth. It is used to cut open the leathery shell of the egg from the inside and is then shed.
Newly hatched venomous snakes are fully equipped with fangs and venom in their venom glands, and are capable of inflicting serious bites. While their venom is similar to that of adults, it may differ in composition as snake venoms are often prey-specific and may change as snakes mature and start to feed on different prey. The venom yield of a hatchling is obviously far less than that of an adult and there is no truth in the rumour that juvenile snakes are more dangerous than adults because they supposedly cannot control the amount of venom injected when biting.
A number of our snakes are ovoviviparous, retaining the embryos within the oviduct and giving birth to live young covered in a thin membrane, which is easily ruptured. Producing live young has some advantages. Females can spend more time basking to assist with egg development but may feed less and find it more difficult to move. This includes our adders (but not the Night Adders), Rinkhals, Mole Snake and Slug-eaters, to mention a few.
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Johan Marais is the author of various books on reptiles including the best-seller A Complete Guide to Snakes of Southern Africa. He is a popular public speaker and offers a variety of courses including Snake Awareness, Scorpion Awareness and Venomous Snake Handling. Johan is accredited by the International Society of Zoological Sciences (ISZS) and is a FGASA (Field Guides Association of Southern Africa) and SASTM (South African Society of Travel Medicine)-approved service provider. His courses are also accredited by the HPCSA (Health Professions Council of South Africa). Johan is a qualified instructor for the Emergency Care & Safety Institute in Oxygen Administration and Wilderness First Aid and a qualified Basic Life Support instructor.