Underground Temperatures

[Jay Rennemeyer]

I did a little research and found that the ground temperature 4' under the soil is 50-55 degrees. The articles didn't say where. Condisering that sulcatas can burrow as deep as 45 vertical feet, it seems safe to say that they're experiencing similar low temperatures while they're underground. This leads me to believe that my tortoise could spend the night outside where the low for this time of year is 60-70 and it wouldn't cause any detrimental effects. What's your opinion?

 

[Tom]

Not true. Especially for a burrow that is open to the air. I have had many man made burrows over the years for various lizards and tortoises. At a depth of 3-4 feet my burrow stays 79-81 all summer long with highs of 110+ and summer night lows down in the 50s. Very little fluctuation. I the winter the temps hover right around 50 down there with daytime highs in the 60s and night temps in the high 20s to low 30s.

Next item: two years ago my adults dug a burrow that is 22' long at about a 45 degree angle. I don't care to do the math, but that should put it somewhere around 10-12 feet under ground. Temps were around 74 during a mild summer at the bottom.

Further: Remember that sulcata territory winter weather is similar to my summer weather. Their summers are similar to summers in Phoenix, AZ. There is no cool time of year over there. My African friend describes their seasons over there as "Hot or Hotter".

Also remember that 60- 70 above ground out in the open is not the same 60-70 in a burrow or temperature controlled box.

I have see lots of instances of sulcatas surviving in 60-70 degree temps, or lower. I did it myself for a while. That is how I know first hand that warmer is better for them. Because they can survive it, does not mean that it is optimal.

I live in one of the hottest parts of the country. I don't know where you are, but dig a sulcata sized hole 4' deep in the heat of your summer and put a temperature probe down there. I can guarantee it will be warmer than 50-55.

 

[mikeh]

I did a little research and found that the ground temperature 4' under the soil is 50-55 degrees. The articles didn't say where. Condisering that sulcatas can burrow as deep as 45 vertical feet, it seems safe to say that they're experiencing similar low temperatures while they're underground. This leads me to believe that my tortoise could spend the night outside where the low for this time of year is 60-70 and it wouldn't cause any detrimental effects. What's your opinion?

The articles most likely refer to solid soil itself retaining fairly steady temperatures few inches below the surface, somewhat depending on type and density of soil. However like Tom described this does not exactly apply to ambient temperatures in an open air circulation burrows.

 

[Jay Rennemeyer]

Thanks for the scoop. Good to know.

 

[Tom]

I have heard that info about cool soil temps before. My uncle told me that about soil temps being that cool all the time at that depth. He and I argued about it a bit. I went back and dug a 4' hole and put a temp probe there. It was in the 70s during summer in solid earth. I tested with my temp gun and with a probe in a short side tunnel out of the sun.

Same story story when we had to dig five feet down to get to the septic tank for service. I WISH the dirt was that cool down there. It is hellish trying to do physical labor here in the summer sun.

 

[jaizei]

http://www.builditsolar.com/Projects/Cooling/EarthTemperatures.htm

 

[Tom]

Interesting link J. It shows mean ground temps in my area as 72, with a single spot at 79. Their chart states these numbers are for temps at a depth of 30-50 feet, but this matches my observations in my area at much shallower depths. It also shows the mean temps in the phoenix area as 68 which is surprising to me as its cooler than here.

I'd like to see a chart showing seasonal highs and lows at various depths vs. a mean temp for the year.

 

[mikeh]

Great read Jaizei. Thanks. I also though the steadier temps would occur at shallower depths.