Reptile & Amphibian Forums

I found this part of the article to be very compelling:

"Hatchlings from rapidly developing embryos at high temperatures perform poorly on tests of speed and endurance relative to hatchlings from slower-developing embryos at lower temperatures. The slower-developing embryos typically give rise to larger hatchlings than do their rapidly developing counterparts."

Does anyone have any knowledge of bearded dragon hatclings sex being related to cooler or warmer temperatures? I have heard this go both ways. Are they temperature dependent sex creatures or not? TSD or non TSD?

What about the temperature egg development relationship?...

I think possibly using a slightly cooler incubation temperature might procure healthier dragons. Instead of 85 degrees maybe 84 or 83. Maybe even 82 for that matter.

It may take longer for them to develop and hatch but they may be healthier animals as a result of the longer processing/development timeframe.

I know eggs burried in soil go through cooling night time temperatures. Cant be hot in the dirt all the time. What is the incubation time in the wild?

I bet it's far longer than the time we induce by our captive artificial incubation environments.

I think a more cyclical incubation setting would be ideal. Having a thermostat and timers to regulate a higher incubation temp for 12 hours then cool by a few degrees for 12 hours. Even if you did this and keep the day temp at 85 degrees, then dropped a little for night temps. Cyclical like the millions of years of evolution they have undergone in the wild. We mammals think in mammal terms... "warm heat makes baby, is good." Personally I think a real simulation of their natural states of embryotic development would lead to healthier dragons and more successful birth rates.

Just theories for speculation at this point though.

Any feedback on this?

The full paragraph I cut from the larger one I posted below:

Although females of oviparous species deposit their eggs in sheltered positions, the vagaries of climate can result in relative cooling or heating of oviposition sites with associated changes in moisture. This realization has led to considerable research on the effects of these abiotic factors on embryonic development. It is now known that within the range of 68–90°F (20–32°C), incubation time can vary as much as fivefold, and that neonatal viability is inversely related to incubation time. Hatchlings from rapidly developing embryos at high temperatures perform poorly on tests of speed and endurance relative to hatchlings from slower-developing embryos at lower temperatures. The slower-developing embryos typically give rise to larger hatchlings than do their rapidly developing counterparts. In the context of this work, it was found that the sex ratio of hatchling turtles varied depending on incubation temperature. In several species of tortoise (Gopherus and Testudo), for example, almost all embryos became males at low incubation temperatures (77–86°F [25–30°C]), and most became females between 88°F and 93°F (31–34°C). Temperature-dependent sex determination (TSD) is known to be widespread, occurring in 12 families of turtles, all crocodilians, the tuatara, and in at least three families of lizards. However, the effect of temperature differs in the various groups. Most turtles exhibit the pattern described, whereas most crocodilians and lizards exhibit the opposite pattern, females being produced at low incubation temperatures and males at higher ones. In a few crocodilians, turtles, and lizards females are produced at high and low incubation temperatures and males at intermediate temperatures. It is possible that some viviparous species experience TSD, in which case the thermoregulatory behavior of the mother would determine the sex of the embryos, but this phenomenon has not been observed.

The effect of the discovery of TSD has been enormous. Almost all developmental biologists previously believed that sex in higher vertebrates was genetically determined. This phenomenon has important implications for the management of threatened or endangered populations, especially if the program contains a captive propagation component. Unless care is taken to incubate eggs at a variety of temperatures, the program could end up with a strongly biased sex ratio. Reflection on the effects of global warming on reptiles exhibiting TSD generates the worry that extinction could be brought about from widely skewed sex ratios.

To my knowledge bearded dragons are genetically sex determined. Their sex is determined by their genes, not incubation temperatures.

I don't think there is too much variation in temperatures in a dragon's nest in the wild..it really depends on how deep the nest is, as sand/soil is a pretty good insulator and tends to hold a fairly steady temperature. There will be some fluctuations, but I don't know the range.

Only real study I have heard of about nest temperatures are more vegetation formed nests (ie huge pile of grasses and dirt mixed together). I think some crocodilians will pile more vegetation on their nests and remove some to regulate internal nest temperatures,but not sure on this aspect. I do know there is some ground bird that spends alot of time building up and taking down the sand/vegetation on a nest mound to keep a near constant temperature inside the next. Scientists stuck a temperature probe inside the nest with the eggs...and monitored the temperature changes. The bird kept it pretty constant...unfortunately I can't remember the variation (if it was only one or two degrees differences or more/less). If I could remember the name of the bird, I would look it up..but I can't. I think its an Australian bird though...
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PHLdyPayne

Yes but the thing is that the bird is sitting on the nest and constantly maintaining the nest whereas a dragon deposits the eggs and then leaves them.

I know the soil insulates to a certain degree, but after a couple of hour the temperature would have to drop a few degrees.

I spent a good deal of time in the mojave desert in California in the national training center (NTC).

It got hot in the day like nearly 100 degrees then it cooled off quite considerably like down in the 60's at night. Sometimes cooler actually.

There is a bigger temperature fluctuation in arid desert regions.

Bob would know he has been to Australia to see them in the wild:

I met him at a show in Daytona.

http://www.youtube.com/watch?v=FZ4T49nYil4

I read in a book that during the breeding season in australia they day time and night time temps fluxuate only 10 to 15 degrees, if thats true, givin a 18 in. to 2 ft. deep hole, the temp would indeed fluxuate a couple of degrees, however, i would think as much as 5 degrees between day and night would be to drastic. I wouldnt be the one to ginny pig my dragons trying, but I know many of you reputable breeders that fill up your incubators and then shelf the rest, and if u shelf them theres no way they are the same temp all the time, yet from what i understand , you get about the same results as incubation however hatch time is usually prolonged. I dont know this from experience, its what i have learned from asking others about thier methods. i agree with the natural way is best, however, naturaly, most offspring fail to make it to juvi age in the wild, and the hatch rate is much lower as well, again what i have read and learned, not speaking from personal experience,But if any one can help, how accurate is this? Thanks

Darren kennedy

I wasn't referring to a typical nest sitting bird, but a bird who buries her eggs in a mound of dirt and vegetation then removes much of this to regulate temperature. Not a typical method for birds, hence why it stuck in my head for so long.

Temperatures underground are much more consistant than temperatures above ground. Even though temperatures in the desert can reach over 100F during the day and drop down to the 40's at night, a foot or two underground, the temperature may only change a degree or two.
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PHLdyPayne