|Click on the links below to read some of the interesting articles and publications about conservation projects we believe in.|
|"Crocodiles vs People"
Published in the "Wildlife Australia" Autumn 1998 edition
|"Harriet, The Galapagos Tortoise, Disclosing One and a Half Centuries of History"
Published in "Reptilia" March/April 1998
|"The Cooperative Conservation of the Fijian Crested Iguana"
By Terri Irwin (Australia Zoo)
|"Breeding Behaviour of the Canopy Goanna"
By Kelsey Engle (Australia Zoo)
|"The Poorly Known Rusty Monitor Varanus Semiremex: History, Natural History, Captive Breeding and Husbandary"
By Richard Jackson (Australia Zoo)(Herpetofauna 35(1): 15-24.)
"Cocodrilos de la Laguna del Carpintero"
|CROCODILE VS PEOPLE: A POSSIBLE SOLUTION?|
Text by Steve and Terri Irwin and Barry and Shelley Lyon
In Australia, the saltie ranges across the north and east between Broome, Western Australia and Maryborough, Queensland. Notwithstanding its common name, this crocodile lives in fresh, brackish and salt waters. It can be encountered in the open ocean, near the shore and in and near estuaries, freshwater rivers and the swamps and lagoons associated with them, sometimes hundreds of kilometers from the coast.
Skins from salties, especially big ones, make excellent, highly prized leather. Demand for skins (for use in shoes, belts, suitcases, briefcases and handbags), supported a significant crocodile-harvesting industry in northern Australia between the end of World War II and the 1960s. Two factors led to the industry's decline and final cessation.
In Queensland, despite such protection since 1974, the Saltwater Crocodile remains on the threatened species list as vulnerable. Since the 1970s, populations of salties have grown. Big crocodiles (usually male) are once again fairly common. They, and smaller crocodiles, have been encountered with increasing frequency, not only by adventurers in remote areas, but also by people in and near cities and towns. Some of these encounters have resulted in fatalities.
This problem can be reduced, possibly even eliminated, by instilling cautious, commonsense attitudes in people whose activities place them in potential contact with salties.
One response to this problem has been devised by the Department of Environment in Queensland. The East Coast Crocodile Management Program was established in 1985 to deal with rogue or nuisance crocodiles. Under this program, potentially dangerous animals are captured and transferred to crocodile farms, wildlife institutions or back to the wild in areas remote from settlement. This strategy is costly and sometimes risky, but seems to work. Certainly the problem is alleviated at least in the short term. However, removing a crocodile from its domain does not mean an area completely safe, merely that it is safer than it was.
Where there are healthy populations, salties usually live in communities. A permanent, deep 1 km long lagoon, where there is a constant food supply, could easily support between six and ten crocodiles. Such a community would have a well-defined social ladder. On the top rung would be a dominant, large male; next would be two or three breeding females; and then, at the bottom of the ladder would be varying numbers of immature crocodiles. Depending on the availability of food, the lagoon might also support another two or three young, sexually mature males. However, the dominant boss of the lagoon would always keep these, through intimidation and fights, on the outer.
In such a situation, removal of the dominant male might solve a people problem temporarily. But, following battles for supremacy, another dominant male will reign, restore order to the lagoon and may again threaten people. Thus, while removal may eliminate immediate threats to human safety, it is hardly a definitive long-term solution. There are problems too for big crocodiles removed from their habitats. Capture and handling can be harsh, sometimes brutal and adaptation to captivity in what are sometimes far from ideal conditions can be difficult, sometimes impossible.
In Queensland, Saltwater Crocodiles occur most commonly in rivers and lagoons associated with the Gulf of Carpentaria. Populations of salties in eastern waters are, by comparison, low with one exception Lakefield National Park, on south-eastern Cape York Peninsula. Lakefield protects the largest population of Saltwater Crocodiles in eastern Queensland. The national park of 537,000 ha is one of only five key areas for C. porosus conservation in Queensland.
In 1994, there were many reports about a large saltie at Old Faithful Water hole, a popular fishing and camping area on the Normanby River. The crocodile, estimated to be 4m long, was swimming close to and approaching people fishing in boats and from the high riverbank. Following assessment by park staff, the area was closed to visitors to reduce potential risks to them and the crocodile. (Illegal shooting had been a problem on the park before.) A decision was made not to attempt to move the crocodile, but to trial a new management strategy that might maintain the well-established social structure in the water hole, yet make it safe again for people. Because of the problems associated with relocation of large crocodiles, the experiment involved capture and harassment of the crocodile and its release to the same waterhole. The aim was to instill fear of people (people shyness) in the crocodile so that he would be reluctant to approach them.
With Lakefields Ranger-in-Charge, Ron Teece, the crocodile was trapped and educated with what appears to be some success. The aversion experiment had three main objectives: Instilling people shyness; maintaining existing social structures in the waterhole; and making it possible to reopen the waterhole to visitors, appropriately educated about his presence.
We arrived at the waterhole on 12 December 1996. A large crocodile, apparently curious, could be seen watching from a distance of about 50m. He continued to watch as a survey dinghy was prepared and as the boat slowly moved upstream.
By two pm that day, the first trap had been erected in a deep, shady location where basking and ambushing sites of crocodiles were located. (The trapping method was developed by Steve and Bob Irwin.) An undulating, melaleuca-lined bank was cleared of foliage and debris, then leveled with shovels to create a large clearing about 2m from the waters edge for the-nylon mesh trap. The trap was rated at 16 tonnes and was supported by sticks hammered into the ground and hemp twine.
The completed rectangular trap was 5 m x 1.5 m x 0.9 m. The entrance was 60 cm from the waters edge and was evenly interwoven with rope attached to 100 kg weight bags. The bags were suspended from a trap ring about 7 m up a tree (on a branch estimated to be able to withstand a force of 400 kg) and attached to a steel rod trigger mechanism.
The trap was baited with 40 kg of fresh feral pig and secured by a short rope spliced over the trigger mechanism. Any jerking or pulling of the bait would cause the weight bags to fall, pulling the mouth of the trap closed in a drawstring effect.
Early next day a stocky 2.6 m female was found in the trap. She was easily released and the trap re-set it was surmised that the capture of one of the target crocodiles mates may have made him wary of the trap, so a second trap was set on a mud bank.
The next morning Old Faithful was in the trap. Within half an hour two top jaw ropes were in place and the crocodile was secured. The mouth of the trap had closed around the base of the crocodiles tail and cloaca, a common occurrence in trapping animals over 3.6 m. To ensure the crocodile was not injured, he was induced to move
fully into the trap. Once inside, a canvas shelter was erected to keep the crocodile damp and so it could be closely monitored. Old Faithful measured 4.2 m from head to tail
with a head length of 56.5cm.
During the first day of capture, team members circled the water immediately in front of the crocodile in two different dinghies, hoping he would learn to fear noise and people. The crocodile soon became agitated whenever an outboard was started and became even more agitated when approached by a 4WD vehicle. The campsite was in
During the night the crocodile was further harassed with spotlights from a dinghy with an outboard motor. Next morning the animal was calm and motionless, but when an outboard motor was started he became distressed and fought to escape. A similar escape attempt occurred when a vehicle approached the camp. These reactions were considered positive signs of stress in response to human activity.
Before his release, a team of eight people straddled and restrained the big crocodile for 15 minutes, while the trap and top jaw ropes were removed. Under the weight and power of the people the crocodile hardly attempted to fight. Such passiveness was a desired response. Then, on the count of three, everyone jumped clear and the crocodile was free. Without hesitating, he walked slowly into the shallow water, swam to the middle of the waterhole with his head above water and then headed straight towards the deepest section. The team was fairly confident Old Faithful had responded to the aversion therapy and that the animal would remain dominant in his territory.
During this survey, fishermen at the waterhole reported seeing a big crocodile lurking at the boat ramp. Subsequent examination of the bank where their dinghy was moored revealed a crocodile slide, but matching an animal less than 3 m long! This crocodile had apparently been feeding on fish offal, backbones and carcasses left on the bank.
The waterhole was surveyed again in October 1997. Old Faithful and a female (about 2.5 m long) were first observed sunning themselves on the opposite bank. The animals quickly responded to the approach of the vehicle and slid into the water and submerged. This was judged to be people shyness.
In subsequent surveys of the waterhole, by Dr Geoff Miller and Dr Mark Read of the Department of Environment, several large crocodiles (more than 2.4 m) were recorded, however, none posed any problem.
This is the second time Steve and Terri Irwin have attempted to deter a declared nuisance crocodile from approaching people. Such a strategy was used in May, 1995 at Escott Station, northern Queensland. A 4.2 m saltie, Nobby, was captured, educated and released. Three years after his education, Nobby is still only rarely seen by property managers and staff. It is hoped that a similar people shyness will deter Old Faithful from approaching people for some considerable time. It is worth noting that large, old crocodiles in Lakefield National Park, that survived the shooting era, are only rarely sighted by rangers or visitors. These crocodiles (longer than 4 m and more than 24-years-old) appear to have maintained their fear of humans for at least 20 years.
To be sure Old Faithful remains wary of people, the crocodile will have to be observed often, at least biannually and there is no guarantee that he will not again pose a threat. Visitors will have to continue to be vigilant! There is only one track into Old Faithfuls Waterhole. A single sign on this track could educate visitors about potential crocodile sightings, Old Faithfuls history, and the value of crocodiles and their conservation in the national park.
All information so far indicates that Old Faithful and Nobby remain dominant in their territories, but avoid any contact with people. In this method, there may be hope for increasing peaceful co-existence between salties and people.
Barry Lyon is formerly a district ranger for Southern Cape York with the Queensland Department of Environment. He and his wife Shelley were the Rangers-in-Charge of Lakefield when it was gazetted a National Park in 1979.
|HARRIET THE TORTOISE||Top|
The Galapagos Tortoise
by Scott Thomson(1), Steve Irwin(2) & Terri Irwin(2)
Gleaning out Harriet's history
Harriet arrived at the Queensland Reptile Park in 1987 from Fleay's Fauna Sanctuary. She already had quite a public life as David Fleay was a prolific writer and she featured prominently in Fleay's books. So where did David Fleay find Harriet? He found her in 1936 at the Brisbane Botanical Gardens and purchased her when they closed their zoo in 1952. David Fleay had very little success in locating Harriet's history but did record that she was here in 1870; we have no idea how David arrived at that date but do have a theory on it which we will discuss later. David did contribute significantly to Harriet's history in other ways, because of David her name is Harriet not Harry, when they realised that he was a she in the late 1950's. We also know where her name came from, she was named after Harry Oakmann, who was the Curator of the Brisbane Botanical Gardens and worked there for over thirty years. But nothing on where she came from.
We were able in time to speak to Harry Oakmann and he introduced us to one of Harriet's former keepers from when she a was at the gardens. Both remember Harriet from as far back as the 1930's but didn't know where she came from, the records from the gardens were searched thoroughly for any evidence and we were able to push the confirmed date back a little further, 1893, the great flood of Brisbane.
The newspapers of the day show people sculling down the main street of Brisbane and for weeks the "Courier Mail", a newspaper in Brisbane, started each edition by thanking the Sydney Morning Herald for printing their papers on their behalf, as their Brisbane office was under some five meters of water. This also spelt the end of the Brisbane Botanical Gardens' records as they were all destroyed in the flood.
At this point we thought the search would be lost to time, we had envisaged reading newspaper after newspaper going backwards in the hope that we could find some mention of her arrival in Australia. We never, thankfully, got around to this, can you imagine trying to find words to the effect of "tortoise arrived" in some 100 years worth of daily newspapers!
The sequence of events that actually uncovered her history were so remarkable that saying that we were a little shocked by it all would be understating the reality and the fact remains that this chain of events is still happening as we speak. On 6 July, 1994 the "Sunday Mail" ran a story on the plight of Lonesome George the last of the Pinta Island tortoises (Geochelone nigra abingdoni) entitled "Lonesome George - the last of his breed", this story had absolutely nothing to do with Harriet but it was the trigger. An old retired historian by the name of Ed Loveday from Mareeba in North Queensland thought he would write a letter to the editor mentioning his recollections of the three, not one, tortoises at the Brisbane Botanical Gardens. We have reproduced his letter in full with this paper (chart 1).
So now we had some names of people, some dates, a starting point at last. In the next two weeks the information systems were extensively searched for additional information. Ed Loveday's earliest recollection of the tortoises, he only ever saw two as one died last century, was in 1922 when he visited the gardens frequently with his parents. Upon interviewing him some more information was gained. The last time he remembered seeing two tortoises at the gardens was between 1925 and 1930, i.e. six years before Harry Oakmann or David Fleay ever saw Harriet. I assumed that the other animal died and was probably buried or dumped somewhere.
We were also able to ascertain that the tortoise that Ed had thought died recently was a very old Red-footed tortoise (Geochelone carbonaria) which died around 1986. Out of necessity we re-examined the previous morphological identification and concluded that Harriet could be a santiago tortoise (Geochelone nigra darwini) as females of this population and the Santa Cruz population are virtually indistinguishable.
Charles Darwin and John Clements Wichkham had crept into the picture now and this gave our first real information. If you want to look at animals in history there is only one sure way to obtain accurate and continuous information, attach the animal to a famous person and follow the person through history. Therefore the history of all the people who could have been associated with Harriet was studied; Darwin, Wickham, Gray, Bell, to name a few. But also places, Darwin's home; Wickham's home, Newstead House and the Oxford University which has some of Darwin's specimens. We also found out that some old city records from Brisbane, before the flood, are possibly stored at the John Oxley Library in Brisbane, but to date we haven't had time to look.
In September of 1994 we were all in Brisbane for a meeting of the Taxon Advisory Group and one of us (ST) was actually going to try and visit the John Oxley Library to have a dig. First, however, I went to the Brisbane Museum to look at a few specimens of Australian turtles, what I eventually found there left no time for the John Oxley Library. Patrick Couper, the Collection Manager there, mentioned to me that they actually had a large tortoise and that it was listed as an Aldabran (geochelone gigantea). I lifted the lid it was a fully spirit preserved tortoise, genus Geochelone, but it was on its back and from what I could see, essentially the plastron, I thought it might be a very large Yellow-footed tortoise (Geochelone denticulata) or something. So we went back up to Patrick's office and looked up the records, apparently this tortoise was given to the Museum by the Brisbane Botanical Gardens and was lodged (not necessarily received) in 1941. I am fairly certain I beat Patrick back to the spirit room.
This time we pulled it out of the tub and righted it so that the animal could be viewed properly. The most significant thing we saw was painted on its back:
"Tom Galapagos tortoise Died 1929 Brisbane Botanical Gardens"
The following day at the Taxon Advisory Group meeting we were actually announcing, for the first time, that we had some information concerning Harriet's history, a rather hasty adit was made about Tom. Since the meeting numerous press releases were made in the hope of obtaining further information from the public, with some success. From all the recent information we were able to deduce how David Fleay arrived at the 1870 date of arrival. We suggest that it was actually the earliest date that he could find first hand evidence that she was actually there. We have first hand evidence going back some 73 years from 1995. David first started studying Harriet in 1936, if he was also able to go back about 70 years also, then he would achieve a date of around 1870.
So where are we at the moment? We know that Darwin collected from three populations: Santa Maria tortoise (Geochelone nigra nigra). San Cristobal tortoise (Geochelone nigra cathamensis) and the Santiago tortoise (Geochelone nigra darwini). Based on Darwins notes all the tortoises collected were juveniles and based on the few sizes given they were probably between one and five years old.
We have an account that the three original tortoises were brought to Australia by John Clements Wickham when he moved to Australia and became First Government Resident of Moreton Bay. Wickham was the First Lieutenant of the Beagle under Capt. Fitz Roy, and later Captain of the Beagle. Wickham never went to the Galapagos so he had to obtain the tortoises of somebody else, the most likely person would be Darwin. Currently we are having mtDNA analysis done to confirm the identifications of Harriet and Tom. Tom as a preserved specimen may not work but we feel that he is worth the risk to try anyway. This will be done by Ed Louis of Texas A & M University. We still have to get to the John Oxley Library and Ian Swingland is looking into things from the English end. Well, this is how the story unfolded so far. The difficult thing to conceive is Harriet's age, to bring this into perspective we have constructed a chronology (Chart 2). To do this we interweave some significant human events into a chronology of events Harriet went through, assuming the story is correct. After all, just imagine being some 167 years old!!
First published in "Intermontanus" (Publication of the Utah Association of Herpetologists) Vol. 4. Nr. 5 (1995): 33-35.
(1). Applied Ecology Research Group. University of Canberra. P.O. Box 1. Belconnen, ACT, 2616, Australia.
THE COOPERATIVE CONSERVATION OF THE FIJIAN CRESTED IGUANA
by Terri Irwin
The plight of the Crested Iguana was brought to my attention in April 1994 while attending the Herpetological TAG meeting in Darwin. Terry Boylan, from the Taronga Park Zoo, explained that both B vitiensis and B fasciatus needed attention. B vitiensis was found on the island of Yaduataba in healthy numbers of 4000 to 6000 individuals. However, the National Trust of Fiji was having a difficult time finding funding to maintain this island reserve. Returning to Beerwah, Steve and I agreed to visit Fiji to further field study and find out, firsthand, what could be done to help these iguanas.
Let's save the Fijian Iguanas.
|BREEDING BEHAVIOUR OF THE CANOPY GOANNA (Varanus keithhornei)||Top|
|by Kelsey Engle|
|Australia Zoo (formally Queensland Reptile and Fauna Park), Beerwah, Sunshine Coast|
In 1988 the Queensland Reptile and Fauna Park (QRFP) at Beerwah obtained permits from the Queensland National Parks and Wildlife Service to collect two specimens of V. keithhornei from the wild. Unfortunately, one specimen sustained injuries during the capture and died shortly after arriving at the park. The second specimen, presumed to be a male, flourished in captivity for the next five years in the absence of conspecifics and at this time a second permit to take was granted to allow for the establishment of a captive breeding program at the QRFP. This species in the wild has an elusive nature, making behavioural and/or reproductive observations virtually impossible; hence, a captive situation offered the best opportunities to observe and record this important information. In November 1993 three specimens, one male and two females, were collected from Iron Range in Cape York Peninsula (Irwin 1996 a).
After the death of the original male the three remaining lizards were moved into
Due to the shy nature of these lizards, food initially was left unattended in small feed dishes within the enclosure. However, once established, the lizards would readily take food from the keeper, ensuring that a strict record of the dietary intake of each individual could be maintained. The lizards adapted well to a diet of small rodents and were also offered crickets, beetles, grasshoppers and, very occasionally, small pieces of fruit. Once established, better replicate wild conditions, their diet was modified to consist almost entirely of insects, with a pink mouse only being offered about once every two weeks (Irwin 1996 a, Sprackland 1994 a).
Eight weeks after transferring the lizards to the new enclosure three eggs were found scattered across the floor. These died early during incubation or were, most likely, infertile. Between 1994 and 1997, the two females had produced eight clutches between them. All were hard, often discoloured and failed to hatch. On each occasion the eggs where laid in various locations with neither female seeming to have a preferred laying site. Numerous nest sites were offered including a termite mound, hollow logs (empty or filled with various substrates such as sand, potting mix or sphagnum moss), an open sandpit and an open sphagnum pit. The various nest sites, where possible, were trialed high above the ground as well as at ground level. During this time none of these nests were utilised for egg deposition and neither female was ever seen to investigate any of these options although they had been observed frantically searching for suitable substrate during the period prior to laying (Irwin 1996 a).
After a female had been mated, she became very aggressive towards the male and other female. Bites and scratches would be inflicted, with the aggression reaching a peak just prior to and following nesting activity. Even during the period of suspected ovulation and mating, small scuffles between the females would occur and on occasions aggression would also be shown towards the male. It became clear from this interaction that the smaller of the two females was the dominant animal and due to her persistent aggression, she was removed from the main enclosure and housed alone. Only once eggs had been laid would a female be removed from the male and replaced by the second female.
In order to reduce the females' frantic searching behaviour prior to laying, a nesting box designed to replicate a rotten log was constructed. The box had internal dimensions of 124mm x 680mm x 245mm. It was totally enclosed with a hinged lid for keeper access. The entrance was a small, elongated opening 25mm high and 7.2mm wide, positioned 190mm from the bottom of the box. An overhang of 75mm out from the box and 90mm down the side was placed around the entrance to provide extra security for the female (Fig. 1). The nesting substrate consisted of a layer of damp sphagnum on top of a 110mm layer of moist sand. A gap of approx. 30mm was left at the top of the box. A heat pad was placed underneath the box. Due to external temperature fluctuations, the internal temperature of the box varied from between
The subordinate female was the first to use this nest box for the first time she deposited four eggs overnight on 23 January 1997. These were placed in the incubator at a 1:1 ratio of vermiculite to water by weight. These eggs although appearing better than previous clutches, were still discoloured and probably not fertile. They were discarded within a month of laying. The second female also deposited a clutch of eggs but scattered them throughout the enclosure. These eggs were of a similar appearance and also infertile.
As the lack of fertility was thought to be related to inadequate heating, a heat lamp was installed to allow the lizards to obtain higher body temperatures. This produced a basking site between 42 and 47 C and was frequently use by the male. However, it was rarely used by either female even after a second basking position was offered, allowing both occupants to bask simultaneously
The nest box was also modified in two ways. The sandy nesting substrate was replaced with a moist potting mix as this was though to better replicate the substrate from which V. prasinus hatchlings have been seen to emerge from in the wild (Sprackland 1989). The underfloor heat pad was also replaced with a strip of heating tape (85mm wide) placed along the inside wall of the box, allowing for a 55mm gap without heat at the box entrance. This modification in the placement of the heat source resolved the original problem of the heat increasing as the female dug down and gave the female greater options by providing a horizontal thermal gradient within the nest box. It was hoped that these two minor alterations, would encourage the use of the box for egg deposition.
Matings were observed on 14, 18, 26 and 28 January 1997. Throughout this period the male was constantly observed on top of the female, sometimes seeming to be resting in that position. Copulation was obvious as the tail base of the male would be wrapped entirely underneath the female's and on some occasions it was possible to view the hemipene itself. While the female was receptive to the male, the two were constantly in contact with each other, the female never objecting to the close proximity of the male. , As the time of egg deposition approached the female became less receptive, the male tended to lose interest in her and the pair spent most of their time on opposite sides of the enclosure. Once the eggs were laid the male actually avoided contact with the female. In this instance, by 3 February 1997, the pair was spending less time together and their individual behaviour returned to 'normal' with each lizard sunning at separate locations for most of the day.
This female first entered the nest box at 4pm on 2 March 1997, 47 days after the first observed mating. It is assumed she did not emerge during the night and remained inside the nest box until 8.30am the next morning. Four eggs were immediately removed from the nest box for artificial incubation. These eggs, unlike previous clutches, were full in appearance with no obvious discolouration (Table 1.). The female did not re-enter the box at any stage after egg deposition however, the male did seem more cautious of her at this time indicating possible aggression by the female towards him. At no time during courtship, mating or egg development did this female's food intake vary. However, as with all of the previous nestings, the female was ravenous after laying, snatching all food offered to her. This aggressive feeding behaviour lasted for 2-3 days.
The eggs were discovered nestled under the sphagnum moss and marginally dug into the potting mix substrate. The temperature at the site of egg deposition was 33 °C. The surface of the sphagnum had a thermal gradient from the entrance back, which ranged from 23 - 29°C at the time of egg collection. All eggs were adhered, the entire clutch weighing 57g and an average egg weight of 14.3g.
Both clutches of eggs were placed in plastic containers in a vermiculite: water ratio of 1:1 by weight. Incubation temperature was 29-30 C and humidity was kept as high as possible. Both clutches were also left as single egg masses.
As the cause of the sudden deterioration of this egg was unclear it was decided to trial a different incubation technique. In the past this alternate technique had been used on Green Python (Morelia viridis) eggs with great success (Mannion 1996) and, due to the overlapping distributions of these two species, it was thought that the conditions should be ideal for the V. keithhornei eggs also. The three remaining eggs were placed in a large plastic garbage bin half filled with a vermiculite/water mix at a ratio of 3:1 by weight. The eggs were half-buried and the container sealed with a glass lid. To ensure an even temperature throughout the incubator, a fan was continuously operated to circulate the air. Incubation temperature remained the same ranging between 29-30 C.
On day two of the second clutch's incubation the substrate mixture appeared too dry; no condensation had formed on the lid of the container. A small amount of water was added to the edges of the mix to avoid physically disturbing the eggs. Day three revealed a small amount of condensation forming on the container lid and it was decided that the mixture was sufficiently moist. By day seven the condensation had increased further, although not to the extent of the first eggs.
After 42 days, the presumed infertile egg in the second clutch began to discolour and it was decided to follow the same procedure that was adopted for the discoloured egg in the first clutch. However, as the hypodermic needle was inserted it became apparent that the contents of this egg were virtually solid, the difference in viscosity being attributed to egg infertility. Instead a scalpel was used to slice the egg away from the rest of the clutch revealing its consistency to be similar to gelatine. Again, the attached portions of the shell were carefully removed, resulting in no damage occurring to the viable eggs. This clutch completed the incubation period in the original manner with no further problems being encountered.
c) Hatching and neonate rearing
The eggs of the first clutch began to sweat the day of hatching. The first hatchling emerged on 20 August 1997, 170 days after laying. The second egg hatched overnight and the last hatchling emerged the following day. All three were in excellent condition and extremely active. At hatching each lizard weighed 10g and their total length ranged between 232mm and 251mm (Table 2.).
The second clutch swelled due to absorption of moisture from the incubation substrate. Both eggs looked healthy; however, one egg was noticeably larger than the other. The larger, 'normal sized' egg was first to hatch after 180 days of incubation. This individual weighed 12g at hatching and had a total length of 243mm but did have a considerable amount of yolk sac left unabsorbed. The hatchling was placed into a plastic tupperware container on moist paper towel and left in the incubator until the sac was absorbed.
The second egg began to sweat, but had failed to hatch by the end of that day. Due to concern over the health of this hatchling the egg was manually opened to expose a fully formed but extremely small and weak lizard. This individual also had yolk left unabsorbed and was set up in the same manner as the first lizard. During this time breathing appeared laboured and the hatchling barely moved. It died 3 days after hatching.
The survivor from the second clutch was set up in a similar manner once its health was considered satisfactory. The temperament of this lizard was markedly different. It was extremely nervous when being observed and would not accept food from forceps, hence it was housed separately.
All four hatchlings were very similar in appearance, but were markedly different from their parents' colouration. The markings on the hatchlings were quite vivid, having a black background with distinct silver chevrons across the entire body (Fig. 2.). The head from the eye region forward is entirely silver. As with many varanid species, the juvenile specimens are far more spectacular in colouration and although the body pattern is discernible on the adults the colours have dulled and merged along the greater part of the body.
The small dead hatchling from the second clutch weighed only 5 grams and was donated to the Queensland Museum. Samples from this lizard are being used for genetic analysis of the V. prasinus group.
The behaviour of withholding eggs only to scatter them around the enclosure at a later date, has also been observed in captive V. beccarii, another closely related species (B. Eidenmuller, pers. comm.), as well as captive V. tristis orientalis (Horn & Visser1997) and V. acanthurus (P. O'Callaghan pers. comm.). It is possible that the female's behaviour was a searching response for an unoccupied territory in which to lay her eggs. Similarly, the appropriate biotic or abiotic triggers may not have been in place for oviposition, as noted by Horn & Visser (1997).
Adult V. keithhornei and hatchling V. prasinus have been observed utilising tree hollows in the wild (Irwin 1996 a, Sprackland 1989). These observations, combined with information on the captive breeding of V. beccarii and V. prasinus (Barker 1985, Eidenmuller 1996, Sprackland 1994 b), resulted in the development of the nesting box which was successfully used by the females at the QRFP.
The detection of a gravid female can be difficult in V. keithhornei. In late developmental stages, many varanid species become noticeably distended in the abdomen. This is not the case with V. keithhornei as the abdomen will become only slightly distended and feeding habits will not always alter. This is also said to be true for captive V. gilleni (M. Vincent pers. comm.). For many varanids, changed feeding habits can be a reliable indication of when a female is preparing to nest (Irwin 1996 b). Female V. keithhornei do not dig test holes and there is no investigation of the nest site until immediately prior to laying. The best guide to determining the time of nesting is if copulation is observed, or the male shows a sudden increased interest in the female.
A difference in appearance was noted during incubation between the two egg masses and is likely to be the direct effect of the different methods of incubation adopted for each clutch. The first clutch, which adopted the same technique used at Dallas Zoo for V. prasinus (Barker 1985), did not noticeably change in size throughout the entire incubation period whilst the second V. keithhornei clutch, incubated using the most common technique for varanid egg incubation, showed a substantial change in appearance. The latter absorbed moisture, significantly increased in size and a few days prior to hatching the healthy egg partially collapsed. This scenario has been typical for varanid eggs incubated in this manner at the QRFP in the past (S. Irwin pers comm.; pers obs.). This difference between the eggs' development was also reflected in the hatchlings; the first three being active and strong upon hatching while the second technique produced weak individuals with unabsorbed yolk. It has been suggested that, perhaps due to the drier conditions within the first situation, the developing embryos required the moisture from the egg sack to survive and so absorbed it more quickly (S. Thomson pers. comm.). It has also been suggested that insufficient air circulation toward the end of the development may cause the neonates to emerge before being fully developed. Whether this outcome was a reflection on the physical conditions of the two clutches, or the incubation techniques utilised is difficult to determine and requires further investigation.
The period between mating and oviposition is usually 6-7 weeks, which is longer than the 4-6 week period given by Horn (1980, Horn & Visser 1989). However, the 179-190 day incubation period does compare with the periods collated by Horn & Visser (1997) for nine recorded captive breedings of V. p. prasinus and V. prasinus beccarii. This may be expected due to the close taxonomic relationships between these species and as such initial predictions of incubation were based on this information.
Because of its arboreal habits and cryptic nature, this species offers many challenges for successful captive maintenance, breeding and public display. It is hoped that a greater understanding of the requirements of these lizards in captivity will give us a greater insight into their lives in the wild.
Thank you to Steve Irwin who provided the opportunity to work with this species and many others. His comments, suggestions and enthusiasm were invaluable to not only the writing of this paper but also the success of the project. Chris Banks. Thank you for the time and effort taken in reviewing drafts of this document. Your comments were appreciated and well received. Finally thank you to Paul O'Callaghan who also took the time to review this paper and provided support throughout its development. Thank you all once more.
Table 1. Dimensions of V. keithhornei eggs at oviposition at QRFP.
Egg No. Length (mm) Width (mm)
Table 2. Dimensions of hatchling V. keithhornei at QRFP.
Lizard No. Weight (g) Snout-vent length (mm) Total length (mm)
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By Richard Jackson