TEMPS: Gradient vs. One Temp

[Madkins007]

If this is an old debate, I apologize- I did not find it when I was looking for it.

The traditional idea is that most herps do best when given a range of temps to self-select from- a temperature gradient.

However, some people have said or suggested that at least some species either do not need this or do not benefit from this. Terry Kilgore and a couple of others, for example, says it is not needed for Red-foots, and I believe I have read Ed say that if we could find the 'ideal temp', we could eliminate or reduce gradients (if I remember the posts correctly, and I apologize to anyone if I am mis-representing what they are saying.)

I am not sure I understand the benefits of offering a limited thermal gradient for ANY tortoise species, and would like to hear any reasoning or research on the topic.

(And, just to clarify- I fully agree that we do not need to offer a huge gradient- say 70-90F, and I also agree that we too often offer too hot of a hot spot. The question is not over the right and wrong way to do a gradient, it is if the gradient is needed at all.)

 

[GBtortoises]

I think that the need for a temperature gradient (or no temperature gradient) is based solely on which species you refer to and what their natural environmental needs are. That's where it pays to do some research on their natural habitat, at Terry has with Redfoots.

I keep primarily Northern Mediterranean species; Hermann's, Ibera, Marginateds along with Russian tortoises, who even though are not considered a Mediterranean species, have very similar environmental requirements. With these species I think that a temperature gradient is absolutely necessary, as is a 15-20 day to night time difference for normal activity.

I can't speak so much for Redfoots or similar species but I have absolutely observed Northern Mediterranean species regulating their body temperatures by moving to and from basking areas where temperatures are warmer. This is especially true when they're kept outdoors with only the sun as source of heat.

Based on my tortoises own actions, I would say that a temperature gradient is absolutely needed for them to function at a normal activity level.

 

[Kristina]

Since my Russians have been outside, I have absolutely noticed thermoregulating activity. Our peak temperature so far this year has been 83*F, and as soon as it hit that temperature, my torts hit the shade. They were active in the morning, sitting still in the shade in the early afternoon, and active again in the evening.

My Hingebacks, on the other hand, don't seem to like the heat at all. I have their "hotspot" adjusted to 80*F, and they won't use it. They all crowd on the other side of the enclosure. I mean the FAR side. If I shut the heat lamp off (it is red, by the way, so it isn't that they are hiding from bright light) the utilize that part of the enclosure. My house temps range from 70-76*F. At this point I only turn the lamp on if the temps drop below 70*F. They are eating, breeding, and active, so they must be content.

I think it depends on species, and you cannot conclusively say that tortoises as a whole do/do not need a temperature gradient.

 

[egyptiandan]

I'm thinking Mark is meaning a temperature gradient during the day.
I agree that it's different for different species and it all depends on where they come from.
I think a gradient helps during the day. Say your talking about a Hermanns tortoise in the wild. On a nice sunny summer day, the shaded temperature could be 90F. In the sun it would be 10 to 15F warmer than that, but if you dig down into the ground 4 or 5 inches the temperatures would be about 10F lower than the shade temperature.
So to reproduce those temperature changes you would need a gradient in the enclosure.

Danny

 

[fifthdawn]

I think even within a species, it varies from tortoise to tortoise. My two redfoots have two hides on opposite ends. One end is about 75 degrees and other end is around 85. The hot spot/basking area is in the mid that ranges from 90-105. They're both cherry heads, but they both prefer different temperature. One of them likes the warmer end, and one of them like the cooler end.

The one that likes the cool end just eats the hang around the cool side, sometimes under a the fake plants. This guy never bask with a few exception after eatting.

The one that likes the warmer end comes out alot more often. After eatting, he will always go to the basking spot and bask for hours before going back in to sleep. Sometimes he falls asleep right under the basking spot. Sometimes he would just randomly come out in the morning to bask and go back to his hide.

If humans can have preferences, it would only makes sense that animals would as well whether they're low or highly cognitive species.
I don't think showing preference needs a large sample size. Logically, if the argument is "All tortoise of X species prefer Y temp" then you only need to show one exception to contradict the whole argument. If you can show even one exception, then the argument has to be chnaged to "Some tortoise of X species prefer Y temp."

 

[-EJ]

I've had up to 15 different species with one background temperature and the same general conditions. About half of them have access to a heat lamp to thermoregulate. When the background temperature is 80 to 85 F none of them use the heat source.

It's ironic how some keepers insist that different tortoises have different requirements. If you look at the general behavior you will see that most tortoises have the same requirements but have different behaviors to fulfill those requirements.

 

[chadk]

So Ed, if they are not using the heat source, could that mean the ambient temps are too high? If you provided a 75 degree area, an 85 degree area, and a basking spot, and at various times of the day it will be found in all 3 spots that would tell us one thing. if it only stayed in the 85 zone, that would mean something else, right?

If you only provide warm areas + a basking area, but not a choice for a cooler area (even a hide with cooler temps), then how do you know they would not choose that if they could?

 

[-EJ]

They are eating... growing... behaving normally... I equate that as 'happy'.

If given a gradient... which I mentioned that some have... hot spot is about 100F and they don't use it if the background temp is 80 or better.

So Ed, if they are not using the heat source, could that mean the ambient temps are too high? If you provided a 75 degree area, an 85 degree area, and a basking spot, and at various times of the day it will be found in all 3 spots that would tell us one thing. if it only stayed in the 85 zone, that would mean something else, right?

If you only provide warm areas + a basking area, but not a choice for a cooler area (even a hide with cooler temps), then how do you know they would not choose that if they could?

 

[chadk]

I'm just thinking that if I'm sitting in a sauna, after a while, I'm going to keep away from the heat source and stick to the 'cooler' areas. After a while more, I'm outta there if I have the choice. If I don't have a choice to leave, guess what, I don't...

Or, if I'm sitting in an old texas jail cell during August with its 80 degree ambient room temp and 90% humidity, you better believe that when the sun shines onto the floor through the bars, that I"m going to stay out of that 'basking spot'... I'll eat fine. Sleep fine. Grow. Mate if given the chance (wife visits...). Yet I'd sure appreciate a nice 70 degree corner now and then....

Clearly I"m not a tortoise - but just trying to offer some practicle examples we can relate to.

"they don't use it if the background temp is 80 or better"
Did they use the 70-75 degree corner? If you didn't provide one, how do you know they wouldn't have preferred it?

Now 'not neccessary' for basic survival... sure. But would they use it and 'appreciate' more micro-climates?

 

[-EJ]

You're kind of leaving out a factor... you are a homeotherm... and tortoises are poikilotherms.

You're body temperature is designed to maintain 98.6 and most other homeotherms are higher than that.

When reptiles 'self regulate'... I'm guessing that they are trying to maintain a specific temperature based on the available background temperature and the available ground temperature... that's just a guess on my part.

From a homeotherm's standpoint you might have provided a valid example.

I'm just thinking that if I'm sitting in a sauna, after a while, I'm going to keep away from the heat source and stick to the 'cooler' areas. After a while more, I'm outta there if I have the choice. If I don't have a choice to leave, guess what, I don't...

Or, if I'm sitting in an old texas jail cell during August with its 80 degree ambient room temp and 90% humidity, you better believe that when the sun shines onto the floor through the bars, that I"m going to stay out of that 'basking spot'... I'll eat fine. Sleep fine. Grow. Mate if given the chance (wife visits...). Yet I'd sure appreciate a nice 70 degree corner now and then....

Clearly I"m not a tortoise - but just trying to offer some practicle examples we can relate to.

"they don't use it if the background temp is 80 or better"
Did they use the 70-75 degree corner? If you didn't provide one, how do you know they wouldn't have preferred it?

Now 'not neccessary' for basic survival... sure. But would they use it and 'appreciate' more micro-climates?

 

[chadk]

"I'm guessing that they are trying to maintain a specific temperature based on the available background temperature and the available ground temperature"

That sounds reasonable. Yet unless you know for certain what that majic temp is (for any given tort of a certain species, of a certain age\size, etc), then giving them a reasonable gradient to choose from seems valid.

Just the other day it was about 70 degrees out. Nice and sunny, but not too warm. My torts moved around browsing, and I noticed at certain times they would stop and rest in the cool shade for long periods of time. Then later, they would stop and bask in the sun.

If nothing else, the gradient approach give the torts more reason to move about and get exercise.

 

[fifthdawn]

I guess what he's trying to say is there can be multiple temperature that they will be happy at or specifically, a range of temperature which they will continue to "behavior, eat, grow, etc." Maybe 85 degree is within that range in which they're "content" I'm not saying 85 isn't good but maybe some tortoise will be happier at a constant 90 degree while others would be happier at a constrant 80 degree, but you can see in this case how both of them would still behavior, eat, and grow normally at 85. But there's really no way to tell without a gradient since they're content with 85.

 

[chadk]

Another aspect is that many folks just can't regulate temps precisely. The ambient temps in the room may change from season to season, day to day, and from day to night. While it would be great if everyone could dial in the t-stat to the magic number and leave it, many of us cannot.

By providing micro-climates, we can better represent the outdoor experience where the tort moves around all day finding the temp he prefers. If the day is really warm, he can find cool areas, if the day is cool, he can find a spot to bask in the sun to warm up. And in my case, if it is winter and close to freezing, he can just head back in to the warm tort shed after grazing for a bit.

 

[Madkins007]

To clarify, I did not intend this to be the daily temp fluctuation or night temp drops, although I think that is an interesting discussion as well.

One interesting natural behavior you read about over and over for almost every species is temp-related foraging- only feeding while temps are in the range of about 75-85F (I don't recall all the studies, that is an estimate). This supports the idea that a fairly limited range is the preferred activity zone.

The argument that Red-foots come from the rain forest and do not experience thermal gradients is inaccurate on two levels. First, MOST Red-foots are not from rain-forest, but rather from savannah or scrub forest- even those in the Northern range. Secondly, MOST of the Red-foots range does experience significant temperature swings- season to season, day to night, and even within microhabitats depending on how much sun they get.

(On that topic- don't forget that climatic charts and weather station reports do not reflect the small but significant changes that happen at the tortoise level in the tortoises specific habitats.)

One theoretical argument I have against 'one temp' plans is that almost all animals seem to want different temps for different activities- eating, digesting, sleeping, napping, healing, etc. Of course, I would also agree that these differences are probably not more than about a 10 degrees F range overall.

Then, of course, is the sheerly mechanical aspect. It is often easier to heat a medium-sized habitat with a single heat source than to provide a more even heat- and this seems to lead to the baking temps of 95+F.

............

I also have to say that I tend to agree with Ed on a big point- there may not be as much difference in tortoise care between species as we sometimes think there is. And that makes sense physically. Humans and other mammals have different skin chemistry, fat ratios, surface area ratios, etc. to better deal with wildly different habitats. Tortoises are built pretty much the same world around structurally and anatomically.

Diet is a common element pointed at as a difference. The weed diet for grassland species, a more omnivorous diet for forest species- but there is little evidence that forest species NEED fruit or meat if the weeds part is adequately varied, and in fact most recent Red-foot books de-emphasis the role of fruits and meats. (This is not to suggest that all species need the exact same diet- Chacos needing cacti is an example of an important exception.)

Ed already brought up temps, and we have discussed similar needs for humidity for young'uns before as well.

Maybe, just maybe, it really IS possible to write an 'all in one' care sheet that then has small notes for the rather few things that really ARE different? Of course, this is probably another thread too, isn't it?