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          The information on this page, comes from my own breeding, done with my own animals, unless otherwise stated.

          As far as I know, TSD experiments have taken place in other reptiles, where a clutch of eggs are separated into two groups, and each group is incubated at different temperatures, and the resulting hatchlings sex recorded.

          The people that argue that TSD does not take place in snakes, have not provided me any legitimate info of these experiments being done on snakes specifically.  Only studies on lizards and turtles, where later they mention, they do not "think" TSD takes place in snakes.

          If experiments with snakes, have taken place, as with lizards and turtles, and the results show temperature does not effect snake eggs, then TSD may not be taking place during the incubation period of the snake eggs.

          But, that does not prove that TSD is not taking place during conception or during the formation of the eggs in the female.  My own breeding shows that, sometime during the keeping, breeding, formation of eggs in the females, or incubation of the eggs, at lower temps, can result in clutches with a higher ratio of females.

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          TSD has been discussed a few times in the snake forums, and some people swear it CAN NOT happen, though they can show NO proof.  It has been proven that the sex of some reptiles is determined by temperature during incubation of their eggs, but I can find no info concerning testing snakes only.  Some people say Temps have no influence on the sex of snake eggs, others say they have experienced TSD themselves with their own snakes.  One person told me, that you "must" split the clutch into 2 even groups and then incubate them at different temps, and do this over several breeding seasons, with different pairs of snakes, or you can not prove anything.  I don't think splitting a clutch into 2 groups makes any sense.  What if the sex was determined at conception, or later, during the formation of the eggs in the female?  It could be that the temps in which she is being kept, has influenced the sex.  That would still be considered "Temperature Sex Determination".

My Results

          Initially, I was keeping my Hot Room at 85 - 86 degrees (29.4 - 30 Celsius) at all times.  I was just a collector of exotic venomous snakes, mostly Cobras, but also some Oz/PNG Elapids.  The first specie of snake I ever bred were Eastern (Common) Brown Snakes.  I bred them in Jan. 2003 and Jan. 2005, but never could get them to eat, and they didn't survive.  They were extremely small.  Smaller than any Corn Snake hatchling I've ever seen.  Also, in Jan. 2005, I bred Sri Lankan Spectacled Cobras, without cooling them.  The snakes were kept at 85 - 86 degrees (29.4 - 30 Celsius).  They bred at those temps.  The eggs formed in the female, were laid, and were incubated at those temps.  There was a 12 . 5 sex ratio.  That is 12 males and 5 females for those of you that didn't know.

          I moved to Florida in Sept. 2005, and then I got more into breeding.  I was still keeping the Hot Room at 85 - 86 degrees, but I started cooling the snakes before breeding.  After cooling, I slowly warmed the room back up to 85 - 86 degrees, and after they shed, I put the snakes together.  The following information is on my original pair of Yellow Phase Equatorial (Sumatran) Spitting Cobras (Naja sumatrana), as I have bred the same pair together for 3 years in a row and kept exceptional records.

          The first year they were kept at the temps mentioned above, all year, then cooled, and then warmed back up to the same temps.  They were introduced, and they bred at those temps.  The eggs formed in the female at those temps.  And, the eggs were incubated at those temps.  I incubated the eggs in a 9.75" clear plastic deli cup with the holes in sides of the cup covered with tape, and just 7- 8 pinholes in the deli cup lid, so that no bugs could get in, but the eggs can breath.  A little condensation forms on the inside of the deli cups.  I used a 50/50 mix of vermiculite/water by weight, and left them sitting on a shelf in my Hot Room, at 85 - 86 degrees.  After 64 days, 6 of the 7 eggs hatched and there was a 5.1 sex ratio.  The 7th eggs did not hatch.

          After I saw the 5.1 ratio that first year, I talked to some friends about it.  They suggested I lower the temps.  I immediately lowered the temps I kept the snakes at throughout the year.  Then I did everything exactly the same, with the same pair of snakes at the new, lower temps.  The third year, I lowered the temps more, but only slightly, and did everything else the same.

          The chart below shows that temps can/do have an effect on the sex of the offspring, other than the eggs taking longer to hatch.  If you split the eggs of one clutch, into 2 groups, and sex has already been determined by temps or other factors during their formation in the female, then your test is showing you nothing.  But, when you breed the exact same pair of snakes, over several years, and everything else is the same, except temperature, and you continuously get less males and more females at the lower temperature range, then TSD (Temperature Sex Determination) most likely is taking place.

          In July 2008, I finished my new Snake Room.  It was built inside a steel building, with 2x4 walls, 2x6 ceiling joists, and it is insulated just like a house would be.  I put Luan on the inside walls.  It was then painted white.  I have a good sized A/C unit for cooling, and two oil-filled electric heaters, each controlled by separate Johnson Controls, on separate breakers, and 4 Ceiling fans circulating the air.  Shortly after it was finished, and the smell of paint was gone, I moved the adult snakes into the room.

          Shortly after that, mold started to grow on the walls and ceiling.  I washed it off, but it grew back.  I purchased a dehumidifier and it solved the problem.  But, maybe too late,  I lost a few, otherwise healthy, adult Corn Snakes and King Snakes, and then a few months later during Brumation, I lost my male breeder N. siamensis, my male breeder N. melanoleuca, and a CB'06 female N. sumatrana.  The temps never went below 55 F (13 C). and everything was healthy.  The N. siamensis and N. melanoleuca may have been old animals, but the N. sumatrana was produced here and was otherwise healthy.

          Before moving the adult snakes to the new Snake Room, they were in bedrooms in my house, and I was using the same type heaters, but using Helix Controls instead of Johnson Controls.  The humidity was naturally much lower, and I didn't need a dehumidifier in the house.  Maybe the temps in the new Snake Room were not as low as I thought, since I was using new heat controls and different A/C unit. Maybe the very high humidity or mold had some effect, maybe not, but as you can see, I did everything else the same, but this year I got more males than females.  This was also the first year that the eggs were laid in the new Snake Room, and incubated in the same room in my house as the 3 prior years.

          This year, 2010, I did everything the same as in 2009, but the Temperature and Humidity remained more constant, ie: no radical rise in humidity.  The dehumidifier has worked very well.  The same two adults were bred again, and they produced 10 eggs.  The largest clutch thus far.  One egg went bad quickly, and the other 9 started hatching out after 74 days, and finished hatching after 75 days.  The sex ratio is 5 . 4 once again, showing a higher number of females, at the lower temps.

Naja sumatrana

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          The Chart below shows the results from breeding the exact same pair of Indochinese (Black & White) Spitting Cobras (Naja siamensis), during the same first two years as in the chart above.  As you can see, at the lower temperature, they produced a lower ratio of males and a higher ratio of females, and again took slightly longer to hatch.

          In 2009, I bred a different, younger male, to the same female, because as stated above, my main breeder male died during Brumation.  I've added the info below, but sine it was a different male, the data does not completely apply.

Naja siamensis

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          In 2008, I also bred Central Asian (Russian) Cobras for the first time.  This species used to be bred with some regularity by at least one man in Europe, but you rarely see them now.  As adults they are not one of the more beautiful species of Cobra, but they are in the top 5 when it comes to personality.  I introduced the female to the male on 02/18/08.  I saw them breeding on 3/15 and 3/21, and she laid 8 eggs on 5/2.  They may have bred before I saw them, because the eggs were laid in only 48 days.  Four of the eggs were infertile.  I incubated the 4 good eggs, and the results are below.

Naja oxiana