Reproduction

All living creatures are motivated by two overwhelming primal instincts. These are survival of the individual and survival of the species as a whole.

In the realm of the first instinct falls the daily routine of foraging for food, finding shelter against the hostile elements and defence against, or avoidance of, predation.

In the realm of the second falls the annual rituals of seeking a mate, mating and producing offspring.

Sex and reproduction amongst serpents is of necessity brief. Snakes are loners who do not tend to live with, or care for, mates. Snakes tend to avoid others of their kind as it means competition for food resources. They are not usually hostile during chance meetings though. Neither is a snake much of a mother. The young must fend for themselves the moment they are born.

Sexual Meeting:

In spring, or when it gets warmer, sexually active males will approach any other snake they see - and the reaction of the approached will then determine the outcome of the encounter. If the approached is a male and it acts aggressively a battle will usually immediately ensue. These battles vary from species to species. Elapids and Vipers tend to indulge in a form of ritualised wrestling and no biting takes place. Colubrids on the other hand can get very violent and bite each other severely. Certain species indulge in no combat but follow the female in amicable groups.

Should the approached not react in any particular manner the male snake will then begin the preliminaries to the sexual act. Using the vomeronasal organ, which gets its data from the tongue, the male will determine chemically what sex and species the approached is by the pheromones emitted from its skin. If it is not a sexually receptive female of the right species the male will quickly move off in search of a new mate.


Snakes mating
Should the approached snake be a receptive female the male will then attempt to mate with her. He will place his head on her back, wind his tail around hers and attempt to join their cloacas together. However the female seldom permits such an uncomplicated act and she usually moves off while he is trying to mate. The male usually only succeeds after many hours - or sometimes days - of trying.

The sexual organs of the male consist of two penises - called hemipenes. The hemipene is covered with flexible spines. Once the male succeeds in penetrating the cloaca of the female with one of his hemipenes it will inflate and the flexible spines will prevent it from being easily dislodged. The coupling usually last for an hour or two but sometimes it is as little as a few minutes to as long as a two days. The couple generally lie still throughout the mating but in some cases the female will pull the male along with her as she moves. After mating it is normal for the male to stay close by the female for a few days and then to couple again.
A hemipene

What came first? The snake or the egg?


Snake laying an egg
Approximately 70% of snake species are oviparous. This means the female deposits a number of eggs in a carefully chosen spot. Temperature and humidity must be just right and gravid females will travel great distances to find the correct spot for laying their eggs.

Egg hatching - the hatchling has just cut through the egg shell with its egg tooth
In rare instances the female will "stand guard" over her eggs - never straying far from where they were laid and fighting off predators who would consume them. Some cobras in India are observed to do this. Only one snake actually builds a nest into which the eggs are deposited - the King Cobra (Ophiphagous hannah). The female King Cobra will coil around her nest and guard it.

Many pythons take real care of their eggs - incubating them by regulating temperature by muscular action of their own bodies. They both care for and protect their eggs.


Snake giving birth to live young
The other 30% of snakes give live birth. They are ovovivaparous. Which means they hatch their eggs within their bodies. Nearly all snakes living in cold climates use this method.

Embryonic development.

Fertilization - the ovule and the spermatozoid meeting - takes place high up in the oviduct. (see Anatomy) The fertilised egg then moves down into the oviduct where the uterine glands secrete substances to surround it. The nature of these substances depends on whether the egg is to be laid or gestated within the body. The length of embryonic development depends on species, and within the species on temperature.

The variations are great with a range of 2 to 5 months encompassing most species.

Fecundity.

The clutch of eggs produced by the female shows just as vast a range as gestation times, with between 2 and 50 being within the norm. However the usual range is between 4 and 16 eggs. As females age and increase in size bigger clutches are produced. Another factor influencing clutch size is the frequency of reproduction.

Most ovovivaparous snakes have a litter annually.

Growth and Maturity.

A newborn hatchling is a perfect miniature replica of the snake which gave birth to it - except for its head which is proportionately larger. It has to fend for itself from the moment it is born. Mortality among infant snakes is very high and predation great.

The growth of a newborn snake is indeterminate and continuous. It depends on availability of nutrients and frequency of feeding. Another factor influencing the rate of growth is temperature. In the tropics snakes tend to grow much faster than in temperate climates. All of these factors influence sexual maturity - even within a single species.

Males tend to mature at a younger age than females. In some areas snakes can be sexually mature at nine months while a more normal age is around 2 to 3 years. However the range is once again great. Prairie rattlesnakes in Utah attain sexual maturity at 3 years while in Canada they only do so at the age of seven.

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Copyright: Séan Thomas & Eugene Griessel - Dec 1999.