Tortoise Nest Temperature Data Collection


Well-Known Member
5 Year Member
Platinum Tortoise Club
Jan 17, 2012
Location (City and/or State)
Sacramento, CA (Central Valley)
Thank you Mark for putting this all together. And so glad that I was given the opportunity to be a part of this. Definitely good reading and very interesting. Great way to get the tortoise populations bigger.

I am not sure what tortoises are native to Australia, but considering that there have been a lot of animals who have perished in the fires, this information would be great in helping to re-populate any tortoise species that will need to be replenished there if necessary. It will be great to get better success rates for hatching them for the re-population. I would imagine that you could ideally use this information for any species based on the depth of the nests and the air temperatures. Am I correct in thinking that or am I way off base?

My maths' is not the best, so what is the average percentage in variation of the drops/swings of the nest temps compared to the depth of the eggs laid and air temp variations, which we could then use for all species, as a general formula or would it be different for each species?
Yes, Carol. I have always wanted this type of data to more fully understand, and then predict the best incubation temperatures and even more important for finding best diapause recipes. Only by knowing the relationship between weather data (air temps) and nest temperatures can we extrapolate. We do need to know type of nest site - open or shaded or partial shade. Then depth of nest since some species use depth of nest (sulcata C nigra sea turtles) to allow more open nest sites in hotter climates.

Not sure what you mean by percentage of variation, but a simple chart is valuable. We need to factor sun exposure. But an open nest at 3" can fluctuate 10°F in summer. At 6" this drops to a 7° swing. At 9" it is turning out to be more like 5°. Once at 12" the swing never exceeds 2°F. Certainly the moisture content of the soil and type of soil will affect this as well, but this temp data alone gives us the biggest piece of information for conclusion. The other factors will make a much more minor differences to adjust.

This data also gives us some insight into temperatures tortoise actually do endure. When so many people quote meteorological low temperatures as justification for a tortoise's ability to withstand colder temperatures, we see the mistake. Just a few inches deep in a pallet or pushed under a thick bush or in a overhanging area, the temperatures never drop close to the overnight low. Where temps are the most extreme - russian tortoises, sulcatas they use burrows that would be more stable than a 12" nest. The flat plastron of the tortoise is designed to take best advantage of ground temps. We have all seen in our enclosures their incessant scaping to new substrate as they push into a corner. This is always exposing newer, deeper ground at warmer temps. A sulcata with a cold winter night drop to the 50°s is in a warm burrow at 80°.


Active Member
5 Year Member
Sep 23, 2012
It would be hard to overstate the value of this kind of data - and I appreciate that you've shared the results here where we can all benefit from it. This kind of information is extremely useful beyond just the stated species, because we can use the relationships between soil depth, daily temperature fluctuation, and ambient air temperature to get a rough estimate of diapause conditions for other tortoise species.


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