Snake Egg Incubation
Dr. Jenni Bass
Snake egg incubation times vary and are influenced by several factors. A few weeks after the hibernation or cooling period necessary for the successful reproduction of many oviparous species, a shed will occur, which in females is known as the "pre-ovulatory" shed. At this time the male is often paired with the female, and she should ovulate in the weeks after this shed. The chorion. This layer receives nitrogenous wastes.
Copulation or mating occurs before ovulation, and in most species occurs several times over several weeks. Fertilization is the union of egg and sperm, not the act of mating. This means that the precise date of fertilization is not certain. In addition, snakes are able to store sperm, so fertilization may occur sometime after mating, and in the absence of a male. Just as the time from mating to ovulation varies, so does the time from ovulation until oviposition, or laying.
Pregnancy can be difficult to determine. The snake usually swells in the mid- to hind-section of her body, but in the case of overweight animals, the swelling can be obscured by fat deposits. The snake may bask more and her appetite may decrease. Her body position may change; she may lie on her side or may coil more loosely than normal. Close to the time she will lay, she may be more restless.
Gravid (pregnant) snakes typically shed about two weeks before they lay. This is an important date to note. The swellings of eggs may be visible in lean animals and may be palpated, that is felt, by an experienced keeper or a reptile veterinarian. They may also be visible on a radiograph (X-ray). Ultrasound is the best and safest method of determining if a snake is gravid as well as the number of eggs.
Take care when handling heavily gravid snakes. The follicles prior to ovulation, as well as the eggs in the oviduct, are fragile structures, and have been known to rupture. Once a snake starts, she should finish laying all of the eggs within her oviduct within 24 hours. If this does not occur, call a reptile veterinarian.
The developing snake embryo (early developmental stage) receives nutrition from the large yolk, to which it is attached by an umbilical cord. As the fetus (later developmental stage) develops, the yolk shrinks and sinks, so that the young snake will hatch on top of the egg. The shell contains calcium deposits, but in a lower concentration than in bird or tortoise eggs, hence the more pliable, leathery feel of the snake egg. The shell, under the appropriate conditions of temperature, humidity and gas (that is oxygen and carbon dioxide) concentrations, permits the exchange of moisture and gas, while protecting the embryo.
The three membranes inside the egg, which sustain the growing animal are:
The amnion. This layer surrounds the embryo and controls the immediate fluid environment.
The allantois. This layer eventually fuses with the chorion to form a gas exchange organ when the fetus is sufficiently developed.
Generally, development is faster when temperatures are at the higher end of the range. Incubation at high temperatures is not necessarily desirable, however, as the safety margin will be narrowed, increasing the chances of abnormalities and making lethal temperatures more likely. Most snake eggs should hatch in 45 to 70 days. However incubation times in some species can require months.
Typically colubrid snakes lay 8 to 14 days after the pre-lay shed, and pythons lay 18 to 26 days after the shed. Offer a nesting site at the time of the pre-lay shed, to allow the snake to become accustomed to something new in her environment. The health of the female and the environmental and husbandry conditions play a determinative role. Unlike the female bird, if conditions do not suit her, the female reptile will not lay her eggs.
It is not unusual to see egg binding or other complications in otherwise healthy animals, which simply have not been provided an adequate site to lay. For most snakes, an opaque container with an entrance hole on the top, half filled with one of the moistened substrates discussed above, will suffice. The ovipositorium (nest) should be placed within the temperature gradient of the cage, such that a thermometer at the level of the eggs reads 82 to 86 degrees Fahrenheit. To discourage the snake from laying in her water dish, replace a large dish with one in which she cannot fit to coil.