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Incubation of Sand Goanna (Varanus gouldii) Eggs.

By Brian Barnett, 16 Suspension Street, Ardeer, Victoria, 3022, Australia

(Originally Published in Herpetofauna 11 (1), 31 August 1979, pp. 21-22)

Late in 1978 I received a phone call from a fellow Victorian Herpetological Society member with a Sand Gonna in his collection that had just deposited eggs. As he had no preview experience in incubating reptile eggs I was asked to take change of them . I agreed but suggested that to gain experience he should retain some and eventually I took five eggs and he kept three.

Although our methods of incubation were similar there was a considerable difference in hatching times. His eggs were kept in a container in a snake cage and mine were in similar containers in my incubator, which is on thermostat with a temperature range of 30-32 degrees Celsius. His cage temperatures were slightly lower. The incubator I use for all eggs is kept at this temperature and is constructed from chipboard with a hinged front. The only ventilation is from a 8 cm X 15 cm vent in the front door. Measurements are 90 cm long X 60 cm high X 50 cm wide, and heat is provided by four 25 watt globes in the roof.

The medium mod for these eggs and most eggs in the past has been peat moss, but, due to several eggs being lost through fungus in the last incubating season, I have decided to change over to vermiculite in future . The eggs were examined every second day and a fine spray of water given if thought necessary.

The eggs were deposited on the 29th November 1978 in an eight and a half hour period with the last one be laid early the next day. The female was just over 60 cm in length. Of the three eggs kept by the other member, two were lost in the first week. The third was kept under incubation for approximately ten weeks before it was brought over to me. It appeared to be still a healthy egg but was lacking in moisture to the extent that it was badly caved in. With very fine spraying over the next few days the egg was brought up to a presentable size again.

I have incubated the eggs of many species of reptiles in the past, but this experience was the most trying of all. Most eggs are incubated within a 2-3 month period but these eggs just went on and on. They looked alright and there was no reason to suspect otherwise but patience finally caught up with me after five and a half month and I opened an egg. The embryo was fully formed and apparently not far from hatching. My impatience was controlled and the three remaining eggs that I had incubated since laying finally came through.

The dates of the births (given below) are those at which the young broke through the egg shell and not the date of complete emergence. Once the egg was broken the young lizard remained inside for 1-2 days.

Date of laying 29th November 1978.

  1. Opened 13th April 1979. Fully formed but did not survive.
  2. Born 16th May 1979 (169 days)
  3. Born 19th May 1979 (172 days)
  4. Born 19th May 1979 (172 days)

Waiting for 24 weeks was bad enough but I still had one egg to go which was the surviving egg from the other member. The slight difference in heat between the the two incubators was a major factor in incubating time.

# 5. Born 24th June 1979 (208 days)

All young were healthy when born and measured on average 26 cm, the tail being 15 cm.

Two were retained and two given away. Crickets were offered at first but these were rejected and small skinks were offered which were readily accepted. Although the preference is still skinks a trick method was tried. Feed skinks were collected and the tails only were offered. Thee young monitors accepted these ‘wriggling skinks' but at the same time medium sized crickets were also placed in the cage and amongst the confusion and activity crickets were also eaten. By this method one is accepting crickets now but the other still requires the trick feeding. The advantage with using tails only is that the skink itself can be saved and returned to its exact area of capture in a short time. Thus a population that would have been completely removed for feed will continue to exist.

There has been much discussion concerning the incubation of these eggs and an incubation period of almost 30 weeks leaves a lot of feed for thought. A goanna in the wild would lay its eggs at approximately the same time that these were laid. As the incubation period was controlled at probably the maximum of heat, it is possible that the last egg was closer to the natural incubation time than the others. Taking into account the cooler nights etc I think this is feasible. As the young could not be born in the winter and survive, possibly the natural incubation period could even be longer with the young emerging in the Spring.

© Copyright Brian Barnett.

For perhaps the best ever paper written on incubating snake eggs - again by Brian Barnett - Click here.

Download the egg incubation paper as an MS Word document (better for printing) by clicking here.

Download the pdf version of the egg incubation paper as it appeared in the journal (about 1838 k) by clicking here.

Download Brian Barnett's paper on breeding Coastal Taipans by clicking here.

Download Brian Barnett's paper on breeding Scrub Pythons by clicking here.

Download Brian Barnett's paper on a novel incubation method for Children's Pythons by clicking here.

Download the pdf version of Brian Barnett's and Graeme Gow's paper on breeding Barkly Adders as it appeared in the journal Monitor (about 1.13 mb) by clicking here.

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