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Indian & Burmese Star Tortoises

- incubation techniques -

Burmese Star tortoise, Geochelone platynota, hatchling

Burmese Star tortoise (Geochelone platynota) hatchling

General info

Indian Star tortoise (Geochelone elegans) eggs can be incubated at a constant temperature, but Burmese Star (Geochelone platynota) eggs benefit from, or require, a cooling period before incubation.

Generally, eggs are placed on dry or slightly damp vermiculite, or other suitable incubation medium, and partially embedded (1/3 - 1/2 egg) into the substrate. Humidity in the incubator should be above 60% and up to 80+%.

If the incubator has no built in water troughs on the bottom, you can place a shallow dish of warm water into the incubator to raise the ambient humidity level.

The trick is to get the substrate dampness and the air humidity just right inside the incubator. If the substrate is too wet, eggs can absorb too much water, swell, and crack. It the air is too dry, the eggs can dehydrate or become too tough for the hatchlings to break through. When in doubt, it's safer to keep the substrate a bit too dry than too wet.

Some Star tortoise breeders place eggs on dry vermiculite and then lightly spray the eggs with water as needed. Others strongly advice against egg spraying because this can cause eggs to crack. Instead, small amounts of warm water can be added directly into the incubation substrate without wetting the eggs.

Introducing polluted water into the incubator can contaminate eggs and subsequently kill them. Distilled water is safest to use. It has been boiled to steam, and major bacteria, fungi, and other contaminants have been removed in the process.

Temperature dependent sex determination

Temperature dependent sex determination (TDSD, TSD), if done with accurate incubators and thermometers, has been observed to be quite reliable in Indian and Burmese Star tortoises. The threshold (pivotal) incubation temperature is said to be around 86.9 °F (30.5 °C). Roughly equal number of males and females and produced at that temperature.

Based on TDSD results in Indian Star tortoises, incubation temperatures of 88-89 °F (31.1-31.7 °C) produce more females and 84-85 °F (28.9-29.4 °C) more males. This probably applies to Burmese Stars as well (Dr Liu, 2000, website gone).

Per Fife, eggs incubated at 85-87 °F (29.4-30.6 °C) will result for mostly boys being hatched and eggs incubated at 88-90 °F (31.1-32.2 °C) for mostly girls (Star Tortoises, 2007, see below).

According to Dr Zovickian, a premier US Radiated and Star tortoise breeder, incubation temperatures of 88-90 °F (31.1-32.2 °C) produce females and 84-85 °F (28.9-29.4 °C) produce males in both Indian and Burmese Star tortoises. Based on his extensive experience, correctly done TDSD is almost 100% accurate in Indian and Burmese Star tortoises (Kingsnake forum, 2010).

Caution! Higher incubation temperatures, especially above 90 °F (32.2 °C), are more likely to introduce birth defects.

Hatchlings incubated for female are often sold as "temperature sexed females" (TSF's) or as "temperature sexed males" (TSM's). However, this is NOT a guarantee of sex. Scroll down to the last section on this page.

Burmese Star tortoise, Geochelone platynota, nesting

Burmese Star tortoise nesting in the early evening hours.

Burmese Star tortoise laying eggs

Close up of her eggs in the nest. She laid eight eggs.

Incubating Indian Star eggs

Incubation temperatures for Indian / Sri Lankan Star tortoise (Geochelone elegans) eggs vary somewhat among breeders. Same for the vermiculite dampness, i.e., how much water is mixed with it. Vermiculite to water ratios by weight vary from 1:1 to 3:1. Many breeders use the "squeeze the water out of the vermiculite" method instead of weighing the amounts. Alternately, some breeders use dry vermiculite with no water added.

Below are some examples of published incubation temperatures and humidity levels for Indian Star tortoise eggs. For more details, please read the original publications.

1.) Hans J. Bidmon (Turtles, Proceedings: International Turtle & Tortoise Symposium Vienna 2002, 2006)

2.) Anslem de Silva (The Biology and Status of the Star Tortoise in Sri Lanka, 2003)

3.) Simon Girling, BVMS CertZooMed MRCVS (Pet Owner's Guide to the Tortoise, 2002)

4.) Jerry D. Fife (Star Tortoises, 2007)

5.) Ivo E. Ivanchev (Schildkröten im Fokus Online, 2012:3)

6.) Monika & Johannes Janssen (Radiata #4, 2009)

7.) Gunther Koehler (Incubation of Reptile Eggs, 2004)

8.) Antonio Sanz & Francisco Javier Valverde (Reptilia #9, 1999)

Burmese Star tortoise (Geochelone platynota) hatching

Hatching Burmese Star tortoise (Geochelone platynota). After pipping, I place hatching babies in small deli little cups lined with wet paper towels.

Burmese Star tortoise (Geochelone platynota) hatchling

Just hatched Burmese Star tortoise (Geochelone platynota) with a small residual yolk sac. He will stay in the incubator inside the deli cup until his belly is sealed and flat.

Incubating Burmese Star eggs

Much of the above Indian Star incubation info applies to Burmese Star tortoises (Geochelone platynota) as well, but their eggs benefit from an initial cooling period. This will help break the the arrested development of the eggs known as diapause.

Per Fife, cooling Burmese Star eggs at 65-70 °F (18-21 °C) for about 30 days before incubation increases the hatch rate (Star Tortoises, 2007).

According to Dr Liu, Burmese Star tortoises lay eggs 90-120 days after mating. Clutches are laid at 30-50 day intervals. Eggs are deposited in flask shaped, 15 cm (5.9") deep nests. Females can loose up to 20% of their body weight after nesting (Dr Liu, 2000, website gone).

Below are some examples of published incubation temperatures for Burmese Star tortoise eggs. For more details, please read the original publications.

1.) Jerry D. Fife, Drew Rheinhardt (The Batagur #3, 2013)

2.) Gerald Kuchling, Eric Goode, Peter Praschag (Endoscopic Imaging of Gonads, Sex Ratio and Temperature Dependent Sex Determination in Captive Bred Juvenile Burmese Star Tortoises Geochelone platynota, Asian Herpetological Research, 2011, 2[4]:240-244)

3.) Chris Leone (GardenStateTortoise.com, 2013)

4.) Chris Leone (Reptiles Magazine, Nov/Dec 2016)

5.) Dr Peter Liu (2000, website gone)

6.) Ken Siffert (Tortoise Forum, Mar 2014)

7.) Toronto Zoo, Canada (TorontoZoo.com, Aug 2016)

8.) TSA newsletter (Aug 2003)

9.) TSA newsletter (Aug 2008)

10.) TSA newsletter (Aug 2011)

Buying temp sexed females

Caution! Just because you buy tortoise hatchlings that were supposedly incubated for female, aka as temperature sexed females or TSF's, it does NOT guarantee that the hatchlings will actually be females. Over the years, I have heard of many cases where Burmese Star tortoise hobbyists have bought TSF's that turned out to be males. This has happened to me as well. Always very disappointing.

Numerous reasons could explain why temp sexed females are actually males. Maybe the temperature dependent sex determination in Burmese Stars is not quite as accurate as it's considered to be, or there are other factors influencing the gender development.

Temperature inside the incubator tends to fluctuate somewhat following the room temperature ups and downs. Also, the location of the eggs inside the incubator can make a difference. When I incubate tortoise eggs, I often put 2-3 different thermometers inside the incubator. The readings between these thermometers can easily vary 1-2 °F, sometimes ever more, depending on the location of the probe and the model of the thermometer.

Most breeders do not use super accurate scientific incubators, so the incubation temperature could have been be more or less off the target. Or maybe the thermometers used were not very reliable. The breeder may not know the actual incubation temperature, and in worst cases may not even tell the whole truth to make a sale. Some breeders also prefer to incubate for males in stock that's intended for sale.

 

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