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Python Sexing and Breeding



Proper sexing of a snake is necessary only if the snake is intended for breeding. There are no secondary sexual characteristics that contribute to a major difference in appearance or behavior between the two sexes. While there are minor secondary sexual characteristics, such as the length of the tail and the size of the ventral spurs, without another snake of both sexes to compare it to this method of sexual determination is unreliable. There are several methods to determine the sex of a snake that are far more reliable and accurate. The male copulatory organs are known as hemipenes and are located on both the left and right sides of the tail base and invert into the tail base. It is the presence or lack of these organs that is used to determine the sex of a snake. This is known as a primary sexual characteristic and is the most reliable means of sex determination. Manual palpation of these organs may be attempted in order to evert the hemipenes and is commonly known as "popping". This method is not very reliable, because if not performed properly hemipenes may be present, but not be everted which would lead one to falsely believe that the snake was a female, when in fact it was a male. The most reliable method is to probe for the presence of hemipenes with a special purpose made probe. It is important that this procedure only be performed by experienced individuals to prevent damage to the organs. The purpose made probe is inserted into the tail base toward the tail tip on either side of the midline. The depth that the probe passes determines the sex. If the probe passes deep into the tail base than the presence of hemipenes may be evident. If the probe fails to pass deep into the tail base the absence of hemipenes may be evident and the result would be a determination of a female. Proper probing should always involve probing both sides to double check ones results. Another method of sexual determination is known as Hydrostatic Eversion. This method involves injecting saline into the tail just below the location of the hemepines to the point that the hemepines are everted. This method is not only reliable, but leaves little room for error. Hydrostatic eversion should ONLY be performed by and experienced reptile veterinarian and never attempted by an owner or breeder. The potential for damage to the sexual organs exists if performed incorrectly.


Captive breeding of pythons has greatly increased over the past 15 years and has seen advancements in both the number of offspring being produced and the variations of color patterns and morphs. Most owners will eventually find themselves attempting to breed their pythons at one time or another during the life of the animal. For this reason it is important not only to understand the methods for breeding, but to have an understanding of a python's reproductive biology as well. The male reproductive anatomy is the same for pythons as it is for other species of snakes. The testes are located in the coelomic cavity of the abdomen. The right testis is located high and to the left. All snakes lack an epididymis, which is present in other species of reptiles. The actual copulatory organ is a pair of organs known as hemipenes, which are located in the base of the tail and controlled by a retractor muscle that is used for retraction and eversion. Copulation is performed by everting a single hemipene and inserting it into the cloaca opening of the female. The male effects on the reproductive cycles of females are currently undetermined. While pythons have two hemipenes only one at a time is needed for copulation. Unlike mammals the hemipenes have a single purpose and are used solely for sexual reproduction and do not play a role in the process of eliminating urates. The urates pass straight into the cloaca. The female reproductive anatomy consists of overies that are located in the coelomic cavity of the abdomen and are located in the same position as the male testes. The overies consist of cells, connective tissue, nerves and blood vessels that are enclosed in a tunic. The oviducts themselves have the ability to secrete albumin and serve in shell secretion, but are not a true uterus. The oviducts empty directly into the cloaca through papillae and not into a separate uterus, which all snakes lack. Sexual maturity is usually determined by size with age having a small effect on sexual maturity. In captivity, diet and care play a much more significant role in sexual maturity and development than in the wild. Captive animals may be "power fed" to bring about early sexual maturity, but this method often has long term effects on the overall health of the snake. Most pythons are oviparous, (egg layers). The female oviducts secrete albumin and shell to produce soft leather like eggs. These eggs are then fertilized by the male sperm that was deposited and stored during copulation and will be deposited outside the body where they will develop. The female will stay with the eggs while they the neonates develop within the eggs. It is important to note that the number of eggs that a female produces is directly effected by the cold blooded nature of reptiles. Pythons, as do all reptiles, have a limited amount of energy to expend on reproduction. The results of this energy limit may be seen in the number of eggs produced or the size of the offspring themselves. This energy may be used to produce a large number of smaller offspring or a smaller number of larger offspring. Snakes are known to allocate up to 40% of their total body weight to reproduction. If you were to compare this to a human female it would be the same as a woman giving birth to a single 50 pound baby. Experiments have been conducted in which some of the developing follicles were removed from the female during the early stages of egg development to reduce clutch size to produce exceptionally large offspring. Providing additional hormones during the early stages of egg development to produce larger clutches and smaller offspring has performed the reverse. It is important to be sure that the female is well fed prior to mating. It is also advisable to supplement her food with a vitamin and mineral supplement prior to mating, due to the excess loss of calcium due to egg production. Environmental factors and climatic conditions in pythons effect breeding. General health also plays a key role in sexual reproduction. A snake that is malnourished may not breed and if it is a female it may not survive the entire process. Prior conditioning is recommended to ensure that both the male and female are in the best possible condition prior to breeding. Both the male and the female should remain in separate enclosures until it is time to begin the process of breeding. The snakes should be allowed to cool down for several months prior to introduction. This is vital for the male, since the production of sperm has been linked to this cooling off period. This period also serves to set the mood for mating. Both animals should be fed prior to the cooling off period and allowed to void their stomach and bladder prior to cooling. If not given the opportunity to vacate prior to cooling the contents of the stomach may remain undigested as a result of the lower temperatures. This may lead to complications and serious illness. A thorough veterinary examination of both partners is recommended prior to cooling to ensure the health of both the male and the female. The cooling off period itself should begin around November and last through December. A light cycle of 12-14 hours per day should be maintained and fresh water should be provided at all times during cooling. Following the cooling period the two snakes should be introduced weekly for periods of 24-48 hours and then separated. This introduction should continue for about three months until copulation is noted several times. The determination of a female being gravid may be signaled by a lack of appetite. Once egg development begins the eggs may appear on a radiograph in the early stages. During the later stages of egg development an abdominal mass may be noted and the eggs themselves will be palpable within the female. Once the female is determined to be gravid she should be provided with a nesting box. This may consist of a plastic container large enough for the female to move around in. The box should be half filled with 1 part vermiculite mixed with 1 part water. The lid should be place on the container and a hole cut in the top large enough for the female pass through. Once the female lays her eggs, the eggs should be removed. The eggs may be safely incubated by placing the entire container in a home made incubator and maintaining them at a temperature of 88-90 degrees F. This temperature should be maintained up until two weeks prior to hatching, at which time the temperature should be, reduce by 2 degrees. An incubator may be made by placing the eggs in a ten-gallon aquarium that has been filled of the way up with water. The water should be heated with a submersible aquarium heater. The container of eggs is placed on bricks and elevated above the water. A styrofoam cooler lid is then placed on top of the aquarium to help retain heat and humidity. The temperature and humidity should be monitored closely during incubation and should be maintained for several days prior to the introduction of the egg container. A thermostat is vital to maintaining proper temperature. The eggs should be inspected periodically for signs mold. Any badly molding and collapsing eggs should be removed and are more than likely infertile. When the neonates are ready to hatch they will make a small slit in the eggshell. They will then remain in the shell for 24-36 hours until they absorb all of the egg yolk. During this period they may poke their head in and out of the slit and return back inside the egg. You should never attempt to remove a snake from its egg during this period. The young snakes are not only absorbing the yolk for its nutrients, but are adjusting to breathing air. All of the eggs in the clutch will begin to hatch at about the same time, usually in the order that they were laid. After a week all of the eggs should have hatched. Eggs that fail to hatch at this point are probably infertile. The remaining undeveloped eggs may be gently opened with a razor blade or scalpel to determine if the neonate is still alive and just unable to escape the egg. Care should be taken to ensure that no harm is caused to the snake. The newly hatched young may be removed from the hatching container after they have left the egg and absorbed all of the yolk. They should be placed in separate, clean and dry container with water and maintained under proper heat and humidity. Feeding may take place after the snakes first post hatching shed. Some pythons may often be difficult to start feeding, but do not loose hope. Continue your efforts and you will be rewarded.

All rights reserved. No part of this document may be reproduced in any form or by any means, electronic or mechanical, including information storage and retrieval systems without permission in writing by the author. No liability is assumed with respect to the use of the information contained herein. Printed in the United States of America. Original Edition 1997

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