by Neil Sonnemann
The Olive Python, Liasis olivaceus, occurs across the northern half of Australia and comprises two subspecies. Liasis olivaceus olivaceus is found from the Kimberley area across to Mt. Isa in Queensland. Liasis olivaceus barroni occurs in the Pilbara Region of Western Australia. L. o. barroni is distinguished from L. o. olivaceus by having fewer midbody scale rows (58-63 v. 61-72) and more ventrals (374-411 v. 355-377) Smith (1981). Another species, Liasis papuana occurs outside of Australia Hoser (2000).These are large, brown, terrestrial pythons lacking in pattern. Smith, 1981 notes that specimens preserved in alcohol show no difference in colour between L. o. olivaceus and L. o. barroni
Captive breeding of the Olive Python has been reported by Christian, 1978, Moran, 1988, Ross and Marzec, 1990, and Barker and Barker, 1994. These reports are from L. o. olivaceus, the commonly kept form of the Olive Python. This paper presents breeding data from 12 clutches of the Olive Python L. o. olivaceus held captive in northern Victoria between 1989 and 1997.
MATERIALS AND METHODS
Pythons used in these trials originated from the Kimberley Region in Western Australia, the Top End of the Northern Territory and the Mt. Isa area in Queensland. All the breeding females originated in the Northern Territory or were descended from this founding stock. The single Kimberley female failed to breed.
Being large and terrestrial these pythons require large caging. Adults are housed in ground level wood cages measuring 200 centimetres long, 100 cm wide and 100 cm high. Subadults can be reared in cages 100 cm long, 80 cm wide and 60 cm high. Juveniles can survive in smaller cages of 60 cm long, 40 cm wide and 30 cm high for several months before growing out of them.
The substrate used is crushed rock used in road making, size 7mm, white in colour. This is washed in a cement mixer to remove dust and dirt particles and air-dried. A depth of around 75mm is used in the cages. Various forms of cage heating have been used over the years, ranging from spot-lamps and heating cable in the substrate to under-floor heating. All specimens have been housed in a purpose built heated room. Ambient average room temperatures are presented in Table 4. Throughout most of the year the daytime air temperature in the room is around 30 degrees C , with the night time low dropping down to 20 degrees C. in winter. Supplemental daytime heat is provided by spot globes or heating cables, the temperature in the basking area is maintained in the high 30’s during daylight hours, with a range of 30-40 degrees C. An absolute low air temperature of 17 degrees C has been recorded in the room in winter. Substrate temperatures have been lower than this on occasion with gravel temperatures measuring between 12 and 15 degrees C. Daytime heating has always been available but females will sometimes opt for voluntary cooling during the winter, not using the heat source until after mating when the eggs are developing. Some of the best results were obtained in “cold” caging, however this has inherent risks to the health of the animals from colds and pneumonia.
Daytime heating hours are varied according to the season, from a low of 8 to 9 hours in winter to a high of 14 hours in summer. No heating is used at night, with cage temperatures falling to ambient room temperatures overnight. Olive pythons will bask during the day and coil tightly in the hide boxes overnight in winter to conserve heat.
Temperatures are cycled throughout the year to initiate breeding responses in the pythons. During spring and summer the temperatures are held within a relatively narrow range of highs and lows. When the breeding season begins in autumn the daytime high and nightimeow temperatures are changed gradually, with the lowest temperatures recorded in winter in June and July. Daytime high temperatures are increased to compensate for lower night time temperatures and decreased daylight hours.
A natural photoperiod for northern Victoria is provided by skylights in the room. Cage furnishings consist of the gravel substrate, a water bowl and a hide box constructed of plywood to give a snug fit for the size of the python in the cage. Branches were included in the cages at one time but were not used often and were eventually discarded. Hollow logs have been used but were unsatisfactory when an animal needed to be examined for any reason, being very difficult to remove from the log without scale damage
Specimens are housed one per cage throughout the year except for the short mating period in winter. Using individual housing allows easier feeding and servicing of cages. This is a fairly placid species with most individuals being easy to keep and handle. The occasional irritable specimen is encountered, large ones can be difficult to keep and maintain. Olive pythons tend to have a docile temperament, only biting if greatly agitated Hoser(1981). Defensive behaviour consists of an elevated stance with half-hearted snaps at the intruder, they will bite in defence but prefer not to. Bites due to feeding behaviour are a different matter and are generally painful. Some individuals can become very food-conscious, to the point of biting and constricting anything that touches them. What causes this behaviour is unknown, a regular feeding schedule as opposed to intermittent feeding did not correct the condition, the keeper must be aware of specimens with this tendency and handle them accordingly. I have had Olive pythons in excess of 3 metres bite and constrict first one arm and then the other, they can be very difficult to remove. Running cold water over the body or into the mouth can result in them releasing their hold. No serious injuries have been sustained but bites by large specimens will make you more careful in future dealings with big Olives. Juveniles are usually defensive and snappy; they seem to settle down quite well when feeding regularly during the first year.
Adults are maintained on a diet of laboratory-raised rats and wild caught rabbits. These are fed either freshly killed or frozen and thawed. Food is generally presented to them on tongs, which will elicit a strike and constriction of the food item. Some specimens will take food left on the floor of the cage. Olive pythons can be fussy feeders, often developing a liking for one kind of prey item and ignoring all others. Wild prey items consist of 48% mammals, 26% reptiles and 26% birds (Shine, 1991). Some juveniles have started feeding on birds such as Starlings and Sparrows and then refused to accept rodents. Trick feeding by scenting rodents with bird feathers has worked for a while until they work out what is going on and then they refuse all rodents. These individuals have been reared on a diet of birds alone but it is hard work obtaining enough birds and they do not grow as well as mammal feeders. There is also the consideration of Salmonella poisoning from birds which is discussed under diseases.
A variation of trick feeding was used with large specimens having a preference for mice, rats or birds. This involved tying the preferred dead food item on to the front of a large dead rabbit, cotton cooking twine was used to tie up the back legs of the preferred food and a small bag needle used to attach this item to the head of the rabbit.
Once presented to the specimen the preferred food would be taken and eaten and the rabbit consumed as well. Fussy feeders could also be presented with several rats strung together in order to get a large meal into them.
Frequency of feeding varies throughout the year, typically adults cease feeding during April and resume in spring. Gravid females will refuse food until after egg laying. Juveniles will feed year round if kept warm in winter. Adults are fed ad lib from spring through summer and autumn until they cease feeding for winter. Large adults will accept six to eight adult rats or one large rabbit at one meal. Two or three large feeds are followed by a slough, adult males would be fed about eight to ten rabbits per year, reproductive females require more food volume, being fed about fifteen rabbits per year. Non-reproductive females have a tendency to become very large and obese, growing to lengths in excess of four metres and twenty kilograms in weight. Feeding should be reduced in these animals. Reproductive females are often of intermediate size, directing resources into egg production rather than body size increase. By the end of summer reproductive females should have replaced fat reserves used in egg production. Muttonbird oil has been used as a dietary supplement, no other vitamins or minerals have been used
The sex of individuals is determined by probing the inside of the tail for the presence or absence of hemipenes (Laszlo, 1973). Juveniles have been difficult to sex on occasion with some specimens giving indeterminate results, sexing in these becomes easier as they grow over several months.
The sex of adults can usually be determined visually by the shape of the tail and the presence of larger spurs in the males.
Mating trials are commenced in May and continue through until mid-July when mating activity decreases. There is a window of opportunity when both sexes are keen to mate; key dates I have used for introductions are the 30th. May, 6th. June, 21st. and 22nd. June (the Winter Solstice). Most successful matings resulting in eggs have occurred during this period.
The male is always introduced to the female’s cage, males should locate the female and initiate courtship without delay. If the pair is compatible mating should occur during the first couple of days of introduction. Often there is no interest in mating shown by the male, this may be due to the female not being receptive, the male being too young or any number of other factors out of the keepers control. Sometimes good matings occur followed by a failure of the female to lay eggs, they can be a very frustrating snake to work with. Male combat has been used to induce mating in an otherwise disinterested male but is not considered essential, older males should mate readily without resorting to allowing males to fight. If males are allowed to combat they should be watched closely as intense fighting can occur and one or both males may be injured or killed.
Upon introduction males will push each other around the cage for a while and then the larger or dominant male will constrict the other, if not separated at this stage the result may be one dead male. This can be a difficult operation where both males are large and aggressive. Male combat should not be required but can be tried with the above precautions if all else fails.
A large male around ten feet in length and twelve kilograms in weight died from teeth abscesses after male combat with a smaller male, this male had been in captivity for fifteen years (Bob Withey, pers. comm.). Both sexes will have a pre-mating season slough after fasting for some time in the autumn, they are introduced following this slough.
Males are left with females for about one week then removed for a week and introduced again. If males are cycled through several female cages the system can become unworkable due to males scenting the presence of the previous male. This can result in fighting with the female rather than mating, injuries have occurred to some females because of this. This has included bruising, bites and rakes from the spurs of the males. One male was removed from the female after fighting occurred, the male was so upset it started biting it’s own tail.
If a compatible pair can be found it is best to use the same pairs each year, results seem to be better than continual swapping of incompatible males. Sometimes there is a season where there is no breeding, other years have produced two or three clutches, this may be a result of climatic factors such as a colder than normal year although the reason for this is not known. Most matings have occurred in June (Table 3), and by the end of July most mating activity has ceased. Males are permanently removed at the end of July. Mating is generally required for the production of a clutch of eggs. Clutches have not been produced without the female being with a male, it seems that mating is required to trigger ovulation.
The average time from the first observed mating to egg laying is 85 days, and the average time from the last observed mating is 81 days (Table 2). Therefore egg laying should occur nearly three months after an observed mating.
The gestation period is the time from ovulation to egg laying. Ovulation has been observed on a number of occasions, characterised by a massive mid-body swelling; it appears that the female has just eaten a large meal where in fact nothing has been eaten. A large lump appears in the female for a period of one or two days and then subsides as eggs are distributed more evenly along the body. If this is seen it is a good indication that the female will lay a clutch. Sometimes the females will lie upside down in the hide box or under the basking lamp while eggs are developing. Usually the female refuses food during gestation.
The dates of ovulation have been recorded on only two occasions, 15th. July, 1991 for female number 12 and the 18th. July, 1994 for female number 6. This gives gestation periods of 52 and 51 days respectively (see Table 2 for laying dates).
Most clutches are laid in September, one clutch was laid on the 26th. August and one female laid a clutch in October and one in November, however the egg laying month is September with nine of the twelve clutches recorded in this month (Table 3).
Sometimes females will develop palpable follicles and fail to lay a clutch. Females will have a pre-laying slough on average 29 days prior to egg deposition, the range is 25 to 34 days (Table 2).
Several days before laying the females are often very active around the cage looking for the best site to build the nest, they will often rub their snouts in an effort to escape the confines of the cage. In the last day or two before laying the females will become very reclusive, seldom venturing out of the hide box. Most clutches have been reported during the day, around mid morning or mid afternoon, the reason is unknown but may reflect a warmer time of the day for strenuous activities such as laying eggs. No special provisions have been made for the female, they seem happy to lay the clutch in a dry hide box without sphagnum moss etc. A clutch of Olive python eggs is the size of a soccer ball, and eggs will adhere to each other if left in the clump. After the female has laid the last egg the clutch is removed and the eggs separated prior to artificial incubation. Maternal incubation by leaving the eggs with the female has not been tried due to the dry conditions in the cages and the need to get females back onto food as quickly as possible. Allowing the female to rest for a week and then cleaning the cage substrate to remove all traces of the smell of the clutch will result in the female commencing to feed again. They will lose a lot of weight during the year in the production of a clutch of eggs. In order to try them the following year it is important to feed as much as they can eat over spring, summer and autumn. Females will breed for two or three years in succession and then miss a year, this may be a natural part of their biology.
Artificial incubation has been used with all clutches using standard python egg incubation techniques. Temperature of incubation was 30 degrees C +/- 2 degrees C. A water:vermiculite mixture of 1:1 by weight was used in the incubating containers.
Plastic bread containers were used and would hold three or four eggs each, half buried in the vermiculite. Eggs were separated immediately after laying and before they became adhered to each other. The eggs of olive pythons have relatively thick shells and separation of eggs was easily accomplished up to several hours after laying.
Most eggs were pure white after laying and were candled with a small pocket torch to see if they contained blood vessels, an indication that they are fertile. All good-looking eggs were incubated apart from the obviously small and yellow infertile eggs or slugs. There was a tendency in some clutches towards incomplete calcification of fertile eggs. Sometimes clear patches were apparent on some eggs up to about the size of a fifty cent piece, these resembled water marks and did not seem to affect the viability of the egg. During incubation these patches were sometimes observed to close over and re-calcify. Other eggs were laid with varying degrees of yellow colour on the eggs, resembling the shell of an infertile egg. The size of these patches varied from one third of the egg (most of these were viable and hatched), to half the egg (a couple of these hatched), and eggs with more than half yellow colouring failed to hatch. This yellow part of the shell would become hard during incubation and was difficult to cut with a knife or scissors, attaining the consistency of old leather. The initial yellow greasy area would become clear and translucent before turning hard. In effect this was a dead part of the egg and was not involved in oxygen and gas exchange, nevertheless some hatchlings resulted from these imperfect eggs, usually they were smaller at hatching. Some eggs were pear shaped at laying and later hatched normally. It is always worth incubating eggs even if they do not look good, sometimes they will surprise you and at worst you can always discard them if they die. Some infertile eggs, or slugs, were half calcified; these eggs will decompose rapidly in incubation. Some eggs died during incubation for no apparent reason, other hatchlings have died after becoming entangled in their umbilical cords.
The hatching process for the clutch may take up to a week from when the first egg is pipped to when the last hatchling emerges from it’s egg. The young snakes will often wait in the eggs for one or two days after their heads are seen outside the egg before finally emerging. When the first egg is slit by the hatchling all the other eggs in the clutch are opened by making a lengthwise cut along the egg using a pair of curved nail scissors. This is to ensure the hatchlings are able to breathe and are not stuck in the eggs unable to get out for any reason. Using this method a good hatch rate has been obtained from fertile eggs. Most hatchlings will emerge from the eggs unassisted, however weak or deformed young will require manual removal; sometimes the hatchling may need to be separated from the yolk if it has not absorbed the yolk after two or three days of pipping the egg. These young may be smaller and weaker than the rest of the clutch, however these will soon catch up with adequate nutrition. Sometimes hatchlings are deformed at the time of hatching, more on this in the health section.
Upon hatching all neonates are removed from the incubation containers and placed in individual plastic rearing boxes such as large cake containers. Small grade 3 mm aquarium gravel is used as the substrate in these containers and changed as necessary. A small enamel water dish and a piece of upturned Eucalypt bark as a hiding spot are added to the container. These containers are suitable for young Olive pythons for a short time only until they outgrow them, at this time they require individual cages of appropriate size.
Neonates slough their skin about two weeks after hatching and some can be slow to start feeding. All hatchlings have eaten voluntarily and force or assist feeding has not been required. Ducklings were used for many years as there was a ready supply of day old ducklings available from a nearby hatchery. These were readily accepted and the young pythons were then converted to rats by rubbing the rodents on fresh ducklings. After the ducklings were no longer available the hatchlings which would not eat rats were given chicken heads initially and then starlings, sparrows or finches to start them feeding on their own. They were then converted to rodents by scenting with bird feathers, or by rubbing mice and rats in a bird’s nest kept in the freezer for this purpose. Hatchlings that would not accept dead food would generally take a live finch placed in the cage (Brian Barnett, pers. comm.). Most hatchlings were feeding well on dead rodents by six to eight months of age.
There is some variation in temperament between hatchlings, some are easy going and placid and others are defensive and nervous by nature. Some have changed as they grow from being aggressive to becoming placid, whilst others become more nervous as they grow. Most will settle down well with careful handling to whatever routine is adopted.
Growth rates have not been routinely recorded. Hatchlings average 660 mm in total length at hatching (Table 9) and grow rapidly on a diet of suckling and weaner rats. Adult body size for males is 176 cm and for females 190 cm (Shine, 1991).
In captivity, Olive pythons appear to reach sexual maturity in 3-4 years, although the majority of captive breedings have occurred with specimens 8-12 years of age (Bob Withey, pers. comm.) in Kend (1997).
My earliest breeding of a female Olive python was at around five years of age, however a young pair produced in November, 1991 first bred in September, 1995 at an age of three years and ten months. This was the earliest recorded breeding. These females were relatively large at around 200 to 250cm total length
Males were reproductive at four years of age however the best results were obtained with large older males.
A number of health problems were noted with these animals. Over the time I was breeding them up to fifty specimens of all ages were held captive indoors. The breeding colony consisted of about twelve adults, growing subadults and hatchlings awaiting sale. A brief summary of disease causing death in individuals is as follows:
A variety of disease processes were involved in the death of breeding animals, the most significant being Salmonella infection. This is thought to have originated in the rodent colony although tests for Salmonella in rat faeces were inconclusive. This bacteria is readily found in the environment and can cause disease when present in large numbers in food. It is often associated with poultry, although most of the animals which succumbed to Salmonella were not fed on birds.
Internal parasites were well represented in earlier years, notably Nematodes (roundworms) and Cestodes (tapeworms). These infections were treated with Panacur (Fenbendazole) for the nematodes and Drontal dog worming tablets for the tapeworms. Tapeworms were readily controlled however the nematodes kept recurring and several doses of Panacur over a year or so were required for complete control. These medications were put into food and fed to the adults. Dosage rates used were obtained from Klingenberg, 1993. Juveniles were not treated for internal parasites, on the assumption that they were free of infection.
A disturbing case of genetic abnormality occurred in three clutches. A pair sold to Gavin and Jayne Royle in 1991 produced a clutch of 13 eggs in September, 1995. All 13 hatched of which 9 were healthy and 4 had umbilical hernias. This consisted of defects around the navel region resulting in contortions and deformation of the spine.
Three were euthanised and one was taken for veterinary treatment to repair the hernia but was unsuccessful and the hatchling later died. The same pair of adults produced a further clutch the following year of 16 eggs, 5 hatched and were healthy and normal, the other 11 either died at full term or hatched with umbilical hernias as in the previous clutch. Whilst it was at first thought the deformities were the result of environmental factors such as high cage or incubation temperatures it became clear the deformities were genetic in origin, being carried by the male. This male was later purchased and bred with female number 12, which had no history of deformed young.
The clutch of 15 fertile eggs produced by this pair comprised of 10 normal hatchlings and 4 hatching with umbilical hernia and 1 died in the egg at full term with gross spinal deformities. The male died in August, 1997 (following the mating period) of undetermined cause.