Jean-Michel Le Poder

The following observations represent two successful breeding attempts of Varanus albigularis, the first occurring in 2000, and the second in 2006. Different lizards were involved in each breeding event.
The two V. albigularis involved in the first successful breeding (2000) were a 7 year old male and a 4 year old female, both of which were wild-caught and unrelated. The monitors were kept together in an apartment where they were free to roam the different rooms. Their primary room, which was specially designed for their needs, included a substrate consisting of a sand and soil mixture, atop a concrete floor. Furnishings consisted of large stones and several thick tree branches. Heat and light were provided by six 150 watt reflector bulbs and four full spectrum bulbs (Zoo Med Laboratories, Inc. San Luis Obispo, CA, USA). Their primary room’s daytime ambient temperature was ca. 24-26 °C with basking temperatures ranging between 35 and 40 °C. Night-time ambient temperature varied between 19 and 21 °C depending on the season. The monitors were fed five times a week on a diet of mice, day-old chicks, rats, locusts, and occasionally hard-boiled eggs. Vitamin supplementation was added to the food twice weekly, and water was provided daily.
In the first week of May 2000, the male showed signs of typical varanid courtship behavior, consisting of spasmodic head movements when approaching the female, and tongue-flicking around the female ’s body, especially on the neck and head. This courtship behavior lasted for a period of seven days. Intense copulation began on 12 May, and ended 15 May. Copulation did not occur in the primary room, but instead occurred in the adjacent rooms where temperatures were lower, around 20 °C. On average, copulation occurred four times a day, with short breaks in between where both lizards rested close to each other. After this three day period, both monitors were observed sheltering in the same burrow without any further mating activity. A week later, a large wooden nesting box measuring 180 x 90 cm, was placed in the primary room. The box was filled with a sand and soil mixture to a depth of ca. 35 cm, and was left open for easy viewing. A 100 watt heat lamp was directed onto the nesting substrate, and substrate humidity levels were monitored daily. Nest box temperatures were not recorded. During the last week of gestation before egg-laying, ca. 4 weeks after copulation , the female showed interest in the nest box by repeatedly digging in it. This behavior was observed for several days. At this time, her appetite decreased, and finally refused to feed four days prior to oviposition.
Overnight, between 17 and 18 June 2000, the female deposited a clutch of 21 eggs atop the substrate covering the concrete floor, ignoring the nest box provided (possibly not deep enough). During oviposition, the female positioned herself inside an hollow tree trunk with only her hind limbs and tail exposed, allowing for perfect viewing of the laying process. The female laid her first egg on 17 June at 0000, and her 21st egg on 18 June at 0900. The remaining 3 eggs were laid between 19 June and 20 June atop the substrate covering the cement floor. All 24 eggs were laid at night. The female used her rear limbs to position each egg once laid together into a pile. Eggs averaged 40 g, with an average length of 7 cm and width of 4 cm.
All eggs were removed from their site of deposition, and set up for incubation. Eleven eggs were incubated in a Brinsea Hatchmaster (Brinsea Products Ltd. North Somerset, England, UK), maintained at 30 °C with a humidity of ca. 70-80%. The other 13 eggs were placed in a plastic container inside an aquarium partially filled with water and heated with a 40 watt heat lamp connected to a thermostat. The temperatures ranged between 28-31 °C, and the humidity ranged between 70-95 % . All eggs were partially buried in a water and vermiculite mixture (at ratio of 1:1 by weight).
Of the 24 eggs incubated, 7 successfully hatched; 4 in the aquarium incubator after 150 days of incubation, and 3 in the commercial incubator after 180 days of incubation. The 17 eggs which did not hatch began to look bad towards the end of incubation, and were manually cut open. One egg contained a dead embryo, however the others appeared to be infertile, each containing a gelatinous, reddish mass. All seven surviving hatchlings emerged from their eggs on their own without any assistance. The hatchlings emerged at a rate of one per day, mostly in the early morning or during the night. Upon emerging, two hatchlings still had yolk sacs and umbilical cords attached, which soon fell off after rubbing their abdomens on the substrate.
All seven hatchlings were set up in a large plexiglass enclosure. At night, hatchlings sheltered together under a slab of tree bark. Hatchings began feeding on crickets after 48 h.
The next successful breeding event began in May of 2006 began in May, just like the previous 2000 breeding. Two unrelated lizards were also involved in this breeding; a 6 year old captive bred female originating from the 2000 successful hatching, and an 8 year old wild-caught male. Both lizards were kept together with 8 others adults monitor lizards( 7 Varanus Albigularis and 1 Varanus Salvator ) in one spacious cellar which was designed for the needs of the lizards. Shelters, branches, and stones to climb on were provided, as well as a water container large enough to allow the monitors to fully submerge their body when needed. All copulation occurred in this cellar. Courtship was similar to the 2000 breeding, and lasted for two weeks . Egg laying occurred at night on 2 June 2006, after a gestation period of 30 days from the last observed copulation. Sixteen eggs were laid atop the sand substrate just as in the previous breeding. All 16 eggs were incubated in the same Brinsea incubator at a steady temperature of 30 °C and 90 % humidity. After 180 days of incubation, the first egg began to hatch on the night of 19 November 2006. By the following morning, the hatchling had emerged, and was found laying beside the egg. By 3 December 2006, six more hatchlings had emerged from their eggs. The 9 remaining eggs did not hatch, and appeared to be infertile.
Looking back at the 2000 and 2006 breedings, despite involving different individuals, both events were very similar in regards to the reproductive behaviors observed, as well as the hatching results. In each breeding, 7 monitors successfully hatched from clutches of 24 and 16. A clutch of 25 eggs laid on 24 May 2007, resulting from the same lizards involved in the 2006 breeding, is currently being incubated in the two different incubators used in the 2000 breeding. As with previous clutches, oviposition occurred at night, and once more the female made use of a hollow tree trunk as cover, and deposited the eggs on top of the substrate.

Despite receiving healthy hatchlings from each breeding, the cause for the poor egg viability and hatch rates experienced in both clutches remains unknown. In the wild, it would be expected that female monitors deposit their eggs in safe, secure areas protected from extreme climatic conditions and potential predators. Therefore, depositing eggs on the surface of the substrate is unlikely normal nesting behavior, and suggests that the nesting options provided may be insufficient. Further testing of different nesting media, depths of media, temperature ranges, and moisture content may help resolve this issue, and provide further insight into the nesting preferences of captive V. albigularis.