 |
|
| StarTortoises.net | * Indian / Sri Lankan & Burmese Star Tortoises... plus a few other species... |
|
Burmese & Indian / Sri Lankan Star Tortoises
Other Stars Angulate Tortoise Misc. Pages
|
Indian / Sri Lankan & Burmese Star Tortoises Eggs & incubation
Geochelone elegans eggs. One baby is peeking through the egg. INDIAN / SRI LANKAN STARS (Geochelone elegans) Incubation of eggs Incubation period is variable. Reports range from 47 to 257 days. In captivity, the average is around 90-120 days depending on the incubation temperature. Indian / Sri Lankan Star tortoise eggs can be incubated at a constant temperature, unlike Burmese Star eggs which may benefit from, or require, a cooling period. Eggs are placed on slightly damp vermiculite, or other suitable incubation medium, and can be partially embedded (1/3 - 1/2 egg) into the substrate. This way eggs will stay dry enough, but benefit from the surrounding humidity. You can place a shallow water dish in the incubator, if it has no built-in water troughs. Humidity in the incubator should be above 60% and up to 80-90%. The trick is to get the wetness and humidity just right. If the conditions in the incubator are too wet, the will eggs absorb too much water, swell, and crack. It it's too dry, the eggs may dehydrate or become too tough for the hatchlings to break through. If eggs start "looking wet" over time, there's too much water in the substrate. If in doubt, keep the substrate a bit too dry rather than too wet. In fact, some Star tortoise breeders place eggs on dry vermiculite and then lightly spray the eggs with water as needed. Temperature-dependent sex determination Temperature-dependent sex determination (TSD) has been observed to be quite reliable in Indian / Sri Lankan and Burmese Star tortoises. The threshold temperature is said to be around 30.5 °C. Based on TSD 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). According to Dr Zovickian, a premier US 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 / Sri Lankan and Burmese Star tortoises. Based on his extensive experience, TSD is almost 100% accurate in Indian / Sri Lankan and Burmese Star tortoises (Kingsnake forum, 2010). However, higher incubation temperatures, especially above 90 °F (32.2 °C), are more likely to introduce birth defects. Examples - Incubation temp & humidity (G. elegans) 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 them. Below are some examples of published incubation temperatures and humidity levels for Indian / Sri Lankan Star tortoise eggs. For more details, please read the original publications. 1.) Hans J. Bidmon (Turtles, Proceedings: International Turtle & Tortoise Symposium Vienna 2002, 2006) Egg box is filled with vermiculite that has been covered with fine gravel. Eggs are embedded 1/3 into the substrate. A small amount of water is injected into the vermiculite with a syringe. This is repeated every 3rd week. Eggs are incubated at 28 °C, or are first incubated at 33-34 °C for 80 days and then at 28 °C for the rest of the incubation period. Humidity above gravel is 86%. Incubation takes 86-123 days. 2.) Anslem de Silva (The Biology and Status of the StarTtortoise in Sri Lanka, 2003) Eggs are half buried in wet vermiculite (1:1 vermiculite to water) and incubated at 28.5 °C, or 30.5 °C, or 31.5 °C. Incubation takes 84-166 days. 3.) Simon Girling, BVMS CertZooMed MRCVS (Pet Owner's Guide to the Tortoise, 2002) Eggs are laid 60-90 days after mating in a 12-20 cm (5"-7") deep nest. Eggs are incubated at 29-31°C (83-86 °F). Average incubation lasts 90-120 days. 4.) Jerry D. Fife (Star Tortoises, 2007) Eggs are incubated either at 85-87 °F (29-31 °C) for more males being hatched or at 88-90 °F (31-32 °C) for more females. Humidity in the incubator is maintained above 60%. Eggs are placed on damp vermiculite (2:1 vermiculite to water). 5.) Monika & Johannes Janssen (Radiata No. 4, 2009) Egg container is filled with very moist vermiculite that is covered with a layer of small pebbles. Eggs are place on top and incubated at 32-33 °C for the first two months, and then temperature is reduced to 29-30 °C. Humidity is kept at 70-80%. 6.) Gunther Koehler (Incubation of Reptile Eggs, 2004) Eggs are incubated at 26-30 °C. Incubation lasts 109-147 days. 7.) Antonio Sanz & Francisco Javier Valverde (Reptilia No. 9, 1999) Eggs are half buried in damp vermiculite (3:1 vermiculite to water) and incubated at 31-32 °C to produce more females. Average incubation lasts 90 days.
Hatching Burmese Star tortoise. Photo by Royden Lepp (pwp).
BURMESE STARS (Geochelone platynota) Incubation of eggs Much of the above info applies to Burmese Star tortoises as well, but their eggs may benefit from an initial cooling period. This will help break the diapause (arrested development). Per Fife, keeping the 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). Examples - Incubation temperature (G. platynota) Below are some examples of published incubation temperatures for Burmese Star tortoise eggs. For more details, please read the original publications. 1.) Dr Peter Liu (2000, website gone) Dr Liu incubates Burmese Star tortoise eggs at around 30 °C (86 °F). Eggs are carefully washed and then placed in a plastic box filled with slightly damp vermiculite (1:1 vermiculite to water by weight). Holes are punched to the egg box lid, and the box is then placed into the incubator. Eggs are sprinkled with small amounts of water once a week. If the vermiculite is kept too wet, the eggs may crack. 2.) TSA newsletter, Aug 2008 San Diego Zoo hatched their first Burmese Star tortoises in 2008. First, these eggs were kept at 18 °C (64.4 °F) for one month. Then, they were incubated at 30 °C (86 °F). Baby tortoises hatched at 128-135 days. 3.) TSA newsletter, Aug 2011 At the Wildlife Rescue Center of the Taipei Zoo, Burmese Star tortoise eggs were incubated between 28 °C (82.4 °F) and 30 °C (86 °F). Babies hatched at 184-186 days. 4.) TSA newsletter, Aug 2011 The Rotterdam Zoo incubated their Burmese Star tortoise eggs at 31 °C (87.8 °F). Babies hatched after 150-152 days of incubation.
SMALL INCUBATORS FOR HOME USE Small styrofoam incubators Hovabator Hovabator Choose one of the thermal air (still air) models with no fan. The cheapest Hovabator still air model is 1602N (pic) with a manual temperature controller. Model 1582 has a larger view window, but it's also a bit more expensive. These Hovabators are quite economical. The 1602N runs on 25 watts.
Little Giant Little Giant bird egg incubator (still air model 9200) by Miller Manufacturing Company is another fairly popular incubator used by small scale tortoise breeders. Just like Hovabator, it's made of styrofoam and has two viewing windows. It is usually also available on eBay Reptibator Zoo Med's digital Reptibator Tips Ideally, put the styrofoam incubators in a warm room with a stable temperature above 70 °F. Stabilize the incubator temperature prior addition of any eggs. It may take a day or two of fiddling with the manual temperature controller to get the heat setting just right. Do not turn tortoise eggs during incubation. Keeping eggs in dark during incubation and hatching may be beneficial. You can tape dark paper over the incubator viewing windows to keep the inside darker. Small fridge-style incubators The newer digital incubators that look like mini fridges are popping up everywhere. These ones can heat and cool. They are useful for reptile eggs that require, or benefit from (e.g. Burmese Star tortoise), a cooling period. The automatic cooling feature also protects eggs from overheating. Accu-Temp, Herp-Bator, ReptiPro, etc. This small refrigerator style unit is sold as a reptile egg incubator under several names, including ReptiPro Exo Terra Exo Terra's PT2499 incubator (pic) looks exactly the same as the models above, but it's black in color and has two adjustable shelves. It's usually available on eBay
Lucky Reptile In Europe, this type of incubator is also sold as the Lucky Reptile Herp Nursery II. It's black in color and has one shelf. Tips As with all incubators, you must place a reliable thermometer inside the egg box in these fridge-style incubators and then adjust the temperature according to that thermometer. It's best to put a thermometer in an egg box on each shelf you use. Do not trust the incubator's built-in temperature display alone because it may be several degrees higher than the actual temperature in the egg box inside the incubator. You must test your incubator before use to see what the actual readings for that unit are. For example, to set the top shelf egg box temperature to 86 °F (30 °C), I must set the unit temperature to 92 °F. The unit display shows a temperature variation of 88-94 °F, but the actual temperature inside the egg box placed on the top shelf stays at 85.6-86.8 °F. If you live in a very hot or cold area, or experience frequent power problems, it might be a good idea to plug the incubator into a battery back up surge protector to shield it from current spikes and power outages. Doors of totally sealed-in incubators should be opened briefly every few days to allow for gas exchange. Oxygen in and carbon dioxide out. For the same reason, covered egg boxes in the incubator should have perforations. Towards the end of the incubation, open the door daily. Again, keeping eggs in dark during incubation and hatching may be beneficial. You can tape dark paper over the incubator's clear door to keep the inside darker.
INCUBATION SUBSTRATES Vermiculite The most popular substrate for Star tortoise egg incubation is vermiculite. When purchasing, look for course, pure vermiculite that is certified to be asbestos free. During incubation, the gas exchange of oxygen and carbon dioxide occurs through the egg shell. Larger grain vermiculite allows for better air flow around the eggs. Other Other incubation substrates used with reptile eggs include perlite, sand, peat moss, and dirt. HatchRite A commercial reptile egg incubation substrate, HatchRite HatchRite is a ready to use product. Do no add water to it. After opening, reseal the bag tightly to keep the moisture in the remaining substrate. Since you don't have to worry about the wetness level in the substrate, using HatchRite has been called the 'incubation for dummies' method. :O) HatchRite is available from many other reptile supply sellers, including those on eBay SuperHatch SuperHatch
SHARE Share your Star tortoise incubation experiences, tips, and photos. Post on the visitor comments board, guestbook, or email me (addy below).
|
| StarTortoises.net | * Star Tortoises - Geochelone elegans, G. platynota, and more... |
startortoises at yahoo dot com |
|
A 
who incubate only a small number of eggs. Hovabator is actually a bird egg incubator invented by the G.Q.F. company, USA, over 30 years ago. It has been used for many years by tortoise breeders with good results.
is another styrofoam box style incubator, just with more advanced digital controls. It's sold on 
